Top Doctor: The hidden dangers in your daily multivitamin | Dr David Seres

Summary

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Podcast Summary: ZOE Science & Nutrition

Episode: Top Doctor: The Hidden Dangers in Your Daily Multivitamin
Host: Jonathan Wolf (ZOE)
Guest: Dr. David Seres, Director of Medical Nutrition and Professor at Columbia University
Release Date: September 4, 2025

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Episode Overview

This episode dives deep into the truth about vitamin and supplement use, exposing the gaps in regulation, the marketing myths, and the real science—or lack thereof—behind daily multivitamins. Dr. David Seres, a physician expert in nutrition for critically ill patients, guides listeners through the surprising legal history, scientific evidence, and practical advice for those considering supplements. Throughout, the conversation maintains an engaging, myth-busting tone, empowering listeners to critically evaluate their supplement choices.

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Key Discussion Points & Insights

1. The Origins & Regulatory History of Vitamins

• Initial Breakthroughs:
  Vitamins once offered miraculous cures for severe deficiencies (scurvy, rickets, goiter).

  • [03:02] Dr. Seres:
    “The whole nickname of British sailors as limeys was because they ate limes...because it cured scurvy, because there's vitamin C in limes...”

• From Medicine to Massive Industry:
  America’s supplement industry skyrocketed after the 1994 Dietary Supplement Health and Education Act (DSHEA), which removed nearly all federal oversight.

  • [05:54] Dr. Seres:
    “There was a bipartisan effort...this law...essentially deregulates anything brought to the market that's called a dietary supplement...left specific ways in which the supplements were allowed to advertise suggestively.”

• Hollywood’s Role – Mel Gibson’s Ad:
  A viral ad campaign with Mel Gibson, dramatizing a raid for possessing vitamins, triggered public outcry and Congressional action.

  • [06:20] Dr. Seres:
    “That advertising campaign got more letters written to Congress than the entire Vietnam War.”

• Consequences:
  Supplements can make structure/function claims (“supports heart health”) without proof, with no requirement for pre-market approval, and minimal regulation compared to pharmaceuticals.

  • [08:21] Dr. Seres:
    “A drug company has to undergo a series of randomized control trials...Dietary supplements are treated as if they were a completely different thing...so they're available without any science necessary...without any safety testing.”

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2. Public Perception, Marketing, and Misleading Claims

• General Misconceptions:
  Most Americans are unaware just how unregulated supplements are.

  • [09:59] Dr. Seres: “I don't think so, no.”

• Marketing Outpaces Science:
  Companies use suggestive, science-sounding claims that skirt direct disease treatment language.

  • [11:08] Dr. Seres: “I could...put...crushed up rose hips and tell you that it supports your kidney health and make a lot of money. There's really nothing that precludes that.”

• Scientific Spin:
  Supplement manufacturers frequently cite weak evidence, cherry-pick studies, or even use experimental cell data irrelevant to real-world health.

  • [16:19] Dr. Seres:
    “...if you do A and get B and do B and get C and do C and get D, the likelihood of doing A and getting D is close to zero because of all the intervening processes...it's never a straight line in biology.”

  • Example: Prostate Cancer Study
    Supplement levels in the body were assumed to be a cause, but large RCTs found that vitamin E and selenium supplementation increased, rather than decreased, cancer risk.

    • [18:29] Dr. Seres:
      “...anyone who received either vitamin E or selenium had about 18% increased rate of prostate cancer.”

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3. Understanding the Science—And Its Distortion

• Levels of Evidence:
  Observational studies ≠ cause/effect; randomized controlled trials (RCTs) are the gold standard.

  • [23:27] Dr. Seres:
    “What we really want is a study that gives us information that's actionable, gives us information that talks to us about cause and effect.”

• Manipulation of Data:
  Inflated claims sometimes result from cherry-picking positive results among many negative ones in subgroup analyses.

  • [21:09] Dr. Seres (memory pill litigation):
    “If you take a large enough data set and analyze it enough times, you'll find something...statistically significant but not relevant...they thought they could then claim that they had good evidence that they improved memory...it was a biological impossibility.”

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4. The Role (and Failings) of the Scientific Community

• Scientists’ Shifting Guidelines:
  Mistakes—like the push for low-fat diets—have eroded public trust. Scientists sometimes overstate evidence and fail to communicate its nuance.

  • [31:35] Dr. Seres:
    “It was bad advice. In fact, low-fat diet may in some people at least...predisposed to weight gain...carbohydrates have an effect on appetite hormones...”

• Openness to Change:
  Good science means admitting when previous recommendations were wrong.

  • [32:07] Jonathan Wolf:
    “You recognize a good scientist because they say, oh, I've changed my mind on things.”

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5. What The Evidence Really Shows About Specific Supplements

Vitamins in the General, Healthy Population

• Dr. Seres’s Rule:
  For most, focus on balanced, less-processed foods.
  Only supplement under physician advice for clear deficiencies.

  • [33:06] Dr. Seres:
    “...unless you have an identified risk or deficiency that your doctor has recommended...there is really no benefit to any of these with a couple of minor exceptions.”

Vitamin C

• No benefit for healthy people; possible minor benefit in endurance athletes (lower cold incidence), at lower doses.
  • [35:15] Dr. Seres: “...really no salutary benefit...with one minor exception...intense skiers and marathon runners had fewer colds if they took vitamin C...”

Vitamin D

• “Insufficient” lab ranges were arbitrarily set; mass supplementation is unsupported for most.
• Slight, questionable benefit in elderly (potentially fewer falls).
• Mega-doses are actively harmful (risk of toxicity, calcium deposits).
  • [36:29] Dr. Seres: “Vitamin D is a real headache...randomized controlled trials...have not shown to have much benefit.”
  • [37:19] Dr. Seres: "Vitamin D at high doses can be very toxic. There are real, potentially even deadly consequences.”

Critically Ill & Elderly

• No clear benefit even in ICU patients. Observational associations often due to illness, not deficiency.
  • [43:12] Dr. Seres:
    “...even in that extreme a situation...there's no benefit.”
• Routine multivitamin for elderly? No convincing evidence, potential for harm.
  • [43:44] Dr. Seres: “...still very weak...I really just can't get behind the idea of wholesale supplementation simply because you’re over a certain age.”

Probiotics and Prebiotics

• Most do not contain microbes that colonize the human gut.
• Little evidence of benefit, except in some specific, minor circumstances.
  • [46:35] Dr. Seres:
    “...most of the probiotics are not normal inhabitants of the intestine...they don’t survive much past the stomach...to expect a salutary benefit...seems to me far-fetched.”

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6. Dietary Advice & What You Should Actually Do

• Eat food that resembles its form when it was harvested or alive (“less processed, more fresh”).

• Emphasize a diversity of plants and fiber, but admit evidence is suggestive—not definitive—except for clear deficiency or at-risk groups.

  • [51:05] Dr. Seres:
    “a diet that’s got a lot of things that look more like what it looked like when it was harvested...avoid the heavily processed foods...shift away from meat and animal products..."

• Strongest advice: don't waste your money on supplements unless medically indicated, and beware the potential for harm in the absence of benefit.

  • [53:54] Dr. Seres:
    “It would be look at your diet and don’t go to the vitamin store.”
    • (Final advice—memorable closer)

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Notable Quotes & Memorable Moments

• On the biggest myth of vitamin supplements:
  [02:24] Dr. Seres:
  “The biggest myth about vitamin supplements is that if some is good, more must be better and will have health benefit and will be safe...It’s not true.”

• On how little regulation exists:
  [11:34] Dr. Seres:
  "I could...sell crushed up rose hips and tell you that it supports your kidney health and make a lot of money. There's really nothing that precludes that."

• On biological complexity:
  [16:19] Dr. Seres:
  "It’s never a straight line in biology."

• On changing advice:
  [31:37] Dr. Seres:
  “It was bad advice. In fact, low-fat diet may in some people...predisposed to weight gain.”

• Final actionable tip:
  [53:54] Dr. Seres:
  “It would be look at your diet and don’t go to the vitamin store.”

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Key Segment Timestamps

• [00:57]–[02:35]: Quickfire Myth-busting on Vitamins
• [05:54]–[07:35]: The 1994 DSHEA Law and Mel Gibson ad
• [16:19]–[20:04]: How biology complicates claims and why correlation isn’t causation
• [21:09]–[23:27]: How supplement advertisers twist science and why RCTs matter
• [33:06]–[34:23]: Dr. Seres’s core advice on supplements
• [35:15]–[37:19]: Deep dives into vitamin C and D science/effectiveness & risks
• [39:10]–[43:12]: Vitamins in critical illness—case studies and COVID-19 evidence
• [49:27]–[53:38]: Dietary patterns, limitations of nutrition science, and fiber/plant diversity

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TL;DR—Dr. Seres’ Core Recommendations

• Do NOT take vitamin or other dietary supplements unless you have an established deficiency or a doctor’s advice.
• Supplements are largely unregulated, can make misleading claims, and rarely have supporting RCT evidence.
• Focus on a balanced, minimally processed diet rich in plant diversity and fiber.
• Mega-dosing on vitamins like D can be actively dangerous.
• Science is complex and evolving: be wary of new claims, and be open to changing your mind as new evidence arises.
• If you’re healthy and have no deficiencies, save your money—the best investment in your health is in your plate, not your pills.

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Memorable closer:
[53:54] Dr. Seres:
“It would be look at your diet and don’t go to the vitamin store.”

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Transcript

[A]

Welcome to Zoe Science and Nutrition, where world leading scientists explain how their research.

[B]

Can improve your health.

[A]

We're told vitamins are essential for our health, that they boost our immune system, fight fatigue and protect us from disease. But what if most of it is isn't true? In the 20th century, vitamin supplements were hailed as a breakthrough, curing diseases like scurvy and rickets. But that success story has taken a turn. In the U.S. a law passed in 1994, helped by a Hollywood ad campaign.

[B]

Removed almost all oversight from the supplement industry.

[A]

Since then, a $40 billion business has grown in the shadows. One where marketing beats science and health claims are made with barely any evidence. Dr. David Sears is director of Medical Nutrition and a professor at Columbia University. Over 25 years as a physician nutrition specialist caring for critically ill patients who rely on life saving nutrition support. He's seen how vulnerable people are to misinformation and how hard it is to.

[B]

Tell what really works.

[A]

In this episode, he exposes the cracks in the vitamin industry, reveals how to spot scientific spin, and reveals what could.

[B]

Really work to improve your health. David, thank you so much for joining me today.

[C]

Oh, it's such a pleasure to be here. Thank you so much. I'm so honored to be asked.

[B]

So we have a tradition here at Zoe. We always start with a quick fire round of questions from our listeners. Are you up for that?

[C]

Sure, sure. Fire away.

[B]

And we have some quite strict rules, especially for professors. You can only say yes or no.

[A]

Or a one sentence answer if you absolutely have to.

[C]

Okay.

[B]

Did Mel Gibson help deregulate vitamins in the U.S. yes.

[A]

Can supplements make health claims without real proof?

[C]

Yes.

[A]

Did scientists contribute to an obesity crisis by fearing fat?

[C]

Maybe.

[A]

Can supplements be sold in the US without approval from public health bodies?

[C]

Yes.

[B]

Pretty amazing.

[A]

Final question. What's the biggest myth about vitamin supplements?

[C]

The biggest myth about vitamin supplements is that if some is good, more must be better and will have health benefit and will be safe.

[B]

And it's not true.

[C]

It's not true.

[B]

I love it. I think those are some rather remarkable answers to the Q and A. Mel Gibson has never made it into the Zoe podcast before. So all quite startling. And I'd like to start maybe at the beginning of this sort of supplement story because I understand when they were first discovered, like vitamins were a real breakthrough. They fix deadly diseases. I was brought up at school in England, so they talked about scurvy and sailors would die and they discovered vitamins.

[C]

The whole nickname of British sailors as limeys was because they ate limes and they ate limes because it cured scurvy, because there's vitamin C in limes, and there wasn't vitamin C in the usual diet of a sailor.

[B]

So that is, like, a brilliant example about how vitamins can save lives.

[C]

And there are many others, like the B vitamins, that are added to breads and so forth, at least in the.

[B]

U.S. so what's interesting is today we're in a place where this supplementation is hugely widespread Right. In the healthy population. And the research team here at Zoe Said is now a $40 billion industry. And so I would really like to understand with you, like, how we got here. And maybe we could just start with, like, what these vitamins were originally designed to treat and how successful they were.

[C]

Sure. The history of vitamins is miraculous because there were different deficiencies in different populations in the world, iodine included, which would cause goiter and cretinism in children, vitamin D, as I mentioned, which caused rickets, vitamin C in sailors, et cetera. And each one of these was an enormous public health boon. I think that ever since then, we've been waiting for the next big, huge discovery around vitamins, and I think there aren't any left that we are aware of.

[A]

Why do you think that the promise.

[B]

Of vitamins has become so, like, attractive for people who view themselves as healthy and who are not suffering from, you know, a deficiency that they're aware of or a doctor has told them they have?

[C]

There's a general feeling in being human that one would like to control one's destiny. And health is this mysterious black box that if you are able to do something now that will give you extended health and longevity. That's very attractive to be able to do that. And vitamins have been held out as this without good proof, but nonetheless, the ability to market them in the way that they're marketed, suggestive of health benefits, has fueled this.

[B]

So when did they move from being this sort of niche thing to treat a particular disease to sort of widespread usage here in the States?

[C]

I think it was probably a gradual sort of thing. I know that in the 90s, a law was passed to deregulate the industry, but at the time, there was already enough money in the industry to have made large donations to political campaigns and so forth in order to promote the passage of the law.

[B]

Is that where Mel Gibson comes in, who you mentioned at the beginning? Could you tell me about that?

[C]

There was a bipartisan effort to pass this law called the Dietary Supplement Health and Education act of 1995, and DSHEA or DSHEA as some people call it. And the primary promoters got people to believe that this was nutrition and it was nourishing. And people also believed that the FDA was trying to regulate these substances, when in fact, no such effort was ongoing. And Mel Gibson was hired to do a commercial in which he is in his home, in his kitchen, in his bathrobe, surprised by a SWAT team arresting him because he's got vitamins. And he called for people to write to Congress. And that advertising campaign got more letters written to Congress than the entire Vietnam War.

[B]

Wow.

[C]

It was very successful.

[B]

So the ad was saying that I was going to have my vitamin C taken away?

[C]

Yes.

[B]

What was this legislation going to do?

[C]

So this legislation essentially deregulates anything brought to the market that's called a dietary supplement. And by that it takes away the ability for the US Food and Drug Administration to regulate these substances and left specific ways in which the supplements were allowed to advertise suggestively. So it's actually written into this that you can say that this stuff supports heart health or supports brain health without really any direct evidence of it.

[B]

So that's written into the legislation. It says, we agree that when you sell this supplement, you can say it supports heart health.

[C]

I think that the actual wording may not be there, but these have been agreed to in subsequent rule passing. But these are called structure and functional claims. It's complicated as to how to actually interpret that which actually makes it harder to regulate. But suffice it to say that they're still not allowed to say that they treat or cure any kind of a disease unless it's been approved by the fda.

[B]

And so they are allowed to make these health claims. Is that different from what would happen if you were a drug or if you were something else in terms of the claims you can make?

[C]

Couldn't be more different. So a drug company has to undergo a series of randomized control trials where people are randomly assigned to either the drug or a standard treatment or a placebo and studied over time to determine whether or not the product does what it's supposed to do. And then that research has to pass muster with the FDA in order to be allowed to be sold as a medication or a drug. Dietary supplements are treated as if they were a completely different thing, where they are nutrients. So therefore they must be safe. Thus, we don't want to deprive people of the ability to access them. And so they're available without any science necessary, without any proof of benefit necessary, and frankly, without any safety testing. Although there is some accountability if something is dangerous.

[B]

I think it's a bit shocking, everything that you just said, David.

[C]

Yeah.

[B]

And so basically there was this law, it was supported by this brilliant piece of advertising, which was presumably funded by the industry.

[C]

Presumably. And one can find that on Google. Just put Mel Gibson in dietary supplements.

[B]

And so suddenly they are carved out from the way that you would treat drugs, but also sort of given sort of permission to make claims here.

[C]

Right.

[B]

In a very different way.

[C]

Right.

[B]

I'd like to get onto that in a minute. But before we do that, do you think that most Americans understand how unregulated this industry is?

[C]

I don't think so, no.

[B]

What do you think the impact is, therefore, on people's behavior and their health as a result of this?

[C]

There's a $40 billion industry. There are statistics on how many people take dietary supplements and it's astounding. I'd have to look it up. I don't recall the exact amount, but more than half of Americans take some form of a dietary supplement.

[B]

Now, I know that there are differences between the regulations here in the States and elsewhere. The team says that in the European Union and the uk, which is still basically following the same rules as in the EU, apparently. The European Food Safety Authority has rejected over 90% of submitted claims since it was formed in 2008. Is there anything equivalent in the States that is like looking at these claims and rejecting them or accepting them?

[C]

There's no requirement for submission of a claim to be able to sell these products. So I am not aware of any similar kind of commission.

[B]

So what would prevent you from saying, take this pill, it's going to make your heart healthier. What does in fact in any way?

[C]

Well, you have to say it supports your heart health. But I could be very wealthy, I'm a well established credible nutrition physician, scientist, et cetera, et cetera. I could very easily take my credibility, put it on a label and sell crushed up rose hips and tell you that it supports your kidney health and make a lot of money. There's really nothing that precludes that.

[B]

And does it support your kidney health?

[C]

There's not any direct evidence that taking extra vitamin C or rose hips has any benefit for the kidneys.

[B]

So you're basically saying you could make a claim that you think makes no sense in science and that's fine.

[C]

That's pretty close to it, yes. There has to be some indirect evidence that, I mean, for instance, people who have kidney stones or bladder infections. There is some evidence that increasing the acid level in your urine might help either of Those, but there is no direct evidence of doing so by taking vitamin C has any benefit. In fact, the studies of cranberry juice and cranberry juice concentrate supplementation for urinary tract infections have been pretty much disappointed. Disappointing.

[A]

I like to do a little drum roll when announcing something exciting at Zoe, and that really exciting thing is that our plant based gut supplement Daily 30.

[B]

Is now available in the US.

[A]

Daily 30 sold out in the UK when it launched and now we're expecting.

[B]

It to sell out in the US too. And I think I know why. Because I use it every day. I love it on my morning yogurt.

[A]

Not only does it taste delicious, it actually gives me over 30 plants and plenty of fiber without my having to pop a tasteless probiotic or swirl some suspicious green powder into my water. You know what I'm talking about. Also, unlike so many other supplements, Daily30 actually delivers gut health digestion energy. Daily30's ingredients are designed to improve how you feel and I feel it daily. Since I started taking it, I've noticed that I often don't need my mid morning snack and I feel like I have more energy to take on my busy schedule. And I thought I was doing a good job of eating well beforehand. Of course, I'm just one person and I work at Zoe. However, because we're Zoe, we ran a randomized controlled trial as we developed daily 30 and the results blew us away. And they helped us to create the GUT supplement we sell today. One that's been constantly refined based on the latest research by the scientists that you often hear talk on this podcast. Oh, and if yogurt's not your thing, I know lots of people who tell me that daily 30 tastes delicious. On eggs, on salads, hummus. My wife likes it on pasta. Many Zoe members tell us it's great on avocado toast too. To get it, head to Zoe.com where right now listeners to the podcast can get 10% off by applying the code FeedYourGut at checkout. That's Zoe.com with the code FeedYourGut at Checkout. You can be one of the first in the US to try the GUT supplement. That's changed my day and I know it'll change yours too.

[B]

So we've got this huge industry which is also extraordinarily unregulated, given that it's able to make claims around health originally built on this very legitimate case of like treating diseases. And even now, I mean, we talked a lot about the skepticism, but I think that there are certain people and stages of life when physicians do recommend vitamins, and that's important. Maybe we should talk about that for a second in this context.

[C]

Sure. And I'll be honest. I'm taking vitamin B12 because I actually developed a deficiency. And so I'm not suggesting that in certain situations vitamins aren't absolutely necessary, but. But for the general healthy population, less so.

[B]

So I'd love to discuss how we've gone from these vitamins for people who have a deficiency to this much broader market where they're being sold, sort of with all of these claims and what's really going on so that you can understand it. Because I think what happens is it's very hard to differentiate between products that actually work and maybe even medicines and those that haven't. Could you just help me to understand how the science is being used to sort of trick someone and contrast that with what you would view as the right way to do the science?

[C]

Sure. A couple things. First of all, some of the evidence might come out of a petri dish where a cell might react to a substance. And then that cell being part organ system, that you can sort of take very indirect evidence like that to say, well, it is involved in the normal biology of this tissue, so therefore it supports that tissue.

[B]

I mean, that sounds good. What's wrong with that?

[C]

Well, the problem with that is that it's indirect evidence. And biology is very complicated. It's incredibly, wonderfully complicated in that if there's one reaction to a certain perturbation, there's bound to be other counter reactions in order to keep things smooth. And so I like to say that if you do A and get B and do B and get C and do C and get D, the likelihood of doing A and getting D is close to zero because of all the intervening processes that can happen. It's never a straight line in biology.

[B]

You could see something like in a sort of petri dish, you know, like when I was at school doing biology, and I can show that I add this one chemical and something happens to one cell. But that isn't the same as saying that if I take this ingredient, like as a human being every day, that suddenly I'm less likely to get dementia.

[C]

Right. So the other problem beyond that the biology is complicated, is that there's a lot of good evidence that anything that's an association that's found in nutrition between a level and some sort of health outcome, that those associations are actually more likely due to the underlying condition than they are due to the level of the nutrient. So Let me give you an example. Men with prostate cancer were seen to have low levels of vitamin E and selenium. And so a study was done, a proper study, over 10 years where people were given vitamin E, selenium, both, or a placebo. And anyone who received either vitamin E or selenium had about 18% increased rate of prostate cancer. So the decreased levels that we're seeing were due to the cancer itself, not a cause of the cancer. And subsequent studies have shown not only that there's a causal relationship between vitamin E, selenium and prostate cancer, but also cancer recurrence.

[B]

So you're saying they measured people who had prostate cancer and they discovered that they were low in. You said selenium and vitamin E, vitamin E. And they're like, oh, that looks bad. So what about if we supplement people who don't yet have prostate cancer and hopefully that will mean they don't get prostate cancer. They did a big study where they also compared it with people who didn't get any of these intervention, and they got the exact opposite of what they expected, which is if you took the selenium and the vitamin E, you actually increased your chance of getting prostate cancer.

[C]

That's precisely correct. And this was a very large study. It was, I think, 30,000 men over 10 years. It's called the Ohio Men's Study. And up until recently at least, it was posted on the National Cancer Institute website as a precautionary tale. And there are many more.

[B]

Help us to understand that, because I think a lot of people listening to that will be like, well, that it doesn't sound right. You were low on this thing, and now we're giving people higher amounts. So surely that must stop you getting prostate.

[C]

Well, it doesn't work that way because you have to at least conceive of the notion that you got those low levels because of the prostate cancer, not that the low levels caused it. So it could work both ways. And in this case, it absolutely showed that the low levels did not cause the prostate cancer.

[B]

So this example might be, we were discussing before that we were both a bit grayer than we were maybe when we were younger. So you might say, ah, people who are getting grayer hair are getting older. So if we just stop you getting gray hair, you won't age. But we're both laughing because it's obvious that even if you stopped us getting gray hair, we're going to keep aging.

[C]

Well, take it to the extreme. The more times you breathe, the closer you are to dying. Thus please stop breathing because I'd like you to live for a long time. And there are so many different examples of this happening in biology and in nutrition specifically.

[B]

And so how does this link back to the claims around vitamins? So you were explaining how these vitamin companies take something in a petri dish and then they make a claim about how it's great to take this vitamin. And I think you were then using this example with prostate cancer to show how that doesn't work. How does that turn out for real in a claim that I might see in a supplement, you know, at the drugstore?

[C]

Well, you'll never see that kind of science reflected in those claims because there's no requirement that those claims are any more than suggestive.

[B]

And are there other ways that the supplement industry might use science in a way that sort of deceives you versus like, the reality of what's going on?

[C]

The advertising often says supported by dozens of studies or has been studied by. Unfortunately, one of the only ways to regulate any of this is through legal action in the US and the only way to bring legal action is if there's fraudulent advertising or they break the rules and make claims directly about a disease. One such example was a memory supplement that was litigated for seven years. And finally the company lost their appeal and lost in court and has changed their advertising. But they, for the longest time claimed that the reason that they could say that they helped memory was based on a study that was done. They did something that was completely improper from a statistical perspective. If you take a large enough data set and analyze it enough times, you'll find something. It's a statistical certainty that you'll find something that is statistically significant but not relevant and not properly statistically significant. So they took a subgroup of findings in this study that they had done. It was a randomized trial. But the overall outcome, which was based on validated scoring, which only included the whole thing, that it showed nothing but that these subgroups that they found, they found after 30 or 40 subgroup analyses, they found two that went in the right direction, which made no sense if you looked at which ones were and were not statistically significant. But they thought they could then claim that they had good evidence that they improved memory. It was a biological impossibility that this product would work. It was a protein, and proteins don't get out of the intestine intact, and they most certainly don't get into the brain intact. There are barriers that biology has provided to prevent that from happening. So it really had no chance of working.

[B]

And David, because that's like a really strong story. Are we sure that they don't work? You're saying that they said, hey, we've done this study. We've got these results. We've claimed that this memory pill is gonna make your memory pill better?

[C]

Yes, for sure. Their study, which was done properly in a large group and in a validated memory score, failed. And it's only through manipulation of the statistics that they were able to claim any benefit. What we really want is a study that gives us information that's actionable, gives us information that talks to us about cause and effect. So the majority of research that people hear about on the evening news and so forth is what we call observational. And observational research takes two things to see if they both occur at the same frequency or a similar frequency in a certain situation. So thus, do men with prostate cancer have lower vitamin E levels? Yes, they do. But the problem is, as I've discussed, that cause and effect, and in this situation, it's been shown that the low levels are the effect of the underlying condition, not the cause. In order to be able to speak to cause and effect, you need to do what's called a randomized trial. And a randomized trial takes a population and randomly assigns them to a treatment or a standard of care or a placebo, which is like a sugar pill, if that's the only thing that's different between the two groups, to see whether or not that thing works. Now, biology is complicated. I've said this before. People are very heterogeneous in their makeup and their genetics and their underlying conditions and all of the different things of their environment and their socioeconomic status. And so in order to sort of smooth that out, instead of having white rats that are all of the same genetic makeup, what we have to do is do large studies in order to drown out the potential confounding variables such as I've mentioned.

[B]

And so I'm guessing you're going to tell me that most people selling supplements do not do randomized trials of their supplement before they sell it.

[C]

That's correct.

[B]

Is it quite common nonetheless, to do randomized trials for your supplement?

[C]

It's actually fairly common to find randomized trials done, but usually it's by scientists. It may sometimes be supported by the industry. But the results of most of those studies have failed to show benefit in the general healthy population for any of these supplements.

[B]

Many supplements now have many different things in them, don't they? They're not just a vitamin. There's lots of different things.

[C]

Sure.

[B]

What's the difference between the randomized trial you're describing and saying this is based on science. And I've got papers against these ingredients. Sure, because that sounds good.

[C]

Well, it does, and that's how it's easily used to sell. But you're corrupting the science to say that because. Let me explain it a little bit differently. There's a lot of data, and a lot of data is observational and showing these correlations versus doing good randomized trials, which lead to better conclusions around cause and effect. And what's also confusing is that, yes, okay, maybe it is based on science, but at what level is it science in a petri dish or is it real, actual science in real people or even in animals to show a health benefit from giving more of a substance?

[B]

So we've talked a lot, I guess, about. There have been issues around claims around supplements. I guess it's also true that one of the reasons that there's mistrust around science is that scientists can also make mistakes. Right. And they can change their mind and say that we said something in the past and now we said something now. And I think that that can cause a lot of, like, lots of trust amongst the public.

[C]

I'm glad you raised this because it's one of the things that I think we're suffering from as a society to a great extent that to the point where being an expert immediately makes you suspect that people think that you're just in it for the money or you're in cahoots with the drug companies or whatever. I think we got there by not caring enough about how we message our recommendations and the strength of the evidence on which the recommendations are based. When I say evidence, and when somebody says evidence based medicine, what they're really, really saying is that the quality of the data comes from a variety of levels of evidence where the highest level of evidence is randomized controlled trials. But the lowest evidence of just a case report or two could influence guidelines on which we base our medical practice or our dietary practices, et cetera. So people need to understand these nuances and we've done a terrible job as science of explaining them. Changing major dietary recommendations when we discover that perhaps they were incorrect and basing them on observational studies initially that perhaps didn't really rise to the level of making public health recommendations. Like for instance, I think you mentioned earlier the idea that we should completely do away with all the fat in our diet. And while it's not proven, there was certainly a rapid rise in obesity when people started to adopt that kind of a diet. I think scientists need to look inward at their responsibility for this. But from the science information consumer's perspective, I could fully understand how somebody would look at us changing our mind about something, our eggs in or out this time. I mean, if you know anything about the U.S. dietary guidelines, this was a joke for years that when we change our minds, it suggests we don't know what we're doing or because why I follow guidelines is to live longer, happier and healthier. And the stakes couldn't be any greater than that. You've just told me that what you told me before might have shortened my life or ruined my health. I don't want to listen to you anymore. And for whatever reason, it's been hard to get the scientific community at large to recognize this and to take part in how we communicate this to the public so that people understand these nuances. When we make recommendations, they're the best we've got. At the time, and this happened with COVID people were very angry that the recommendations seem to be moving. I think Dr. Fauci did the best he could, communicating during COVID as to why the recommendations were changing. But that's kind of a new thing that science has really stood back and said, but we're science, we are credible, and you should listen to us as opposed to explaining why the recommendations might change.

[B]

And I guess I can see how this is hard to then know how to navigate because you are putting this really important thing about your health and you're asking experts to help to advise you, and then they change their mind. And then you see all these supplements which tend today to be promoted by, you know, influencers and people that you have this real. You feel, you have this real relationship with, with great confidence.

[C]

Yes.

[B]

And I guess you're looking for that reliability. Before I switch on to what we should do, I would love to talk about maybe nutrition in this context for a minute. Certainly you've mentioned before about, you know, low fat. Where were you on low fat in the past and where are you today?

[C]

Well, I was with all of my colleagues and that was the recommendation, you know, when I early in my career, trying to counsel people on weight loss and so forth, that's what we told people to do because that's what we were all led to believe was the evidence.

[B]

And what is your view on that advice that you gave?

[C]

It was bad advice. It was bad advice. In fact, low fat diet may in some people at least be predisposed to weight gain. So it probably made it harder in order to eat A low fat diet, you've got to eat a relatively high carb diet and carbohydrates have an effect on appetite hormones and so forth that we're discovering now.

[B]

My sort of simple rule after eight years at Zoe is that you recognize a good scientist because they say, oh, I've changed my mind on things. And they also say I don't.

[C]

No.

[B]

So I really like the fact that you're talking about the things you've changed. I agree on that because I think it gives you a lot more confidence about the things that someone says with confidence because they are open to changing their mind.

[A]

Now I think we've sort of unpacked.

[B]

Sort of both the regulatory environment, which is a sort of free for all. We talked about the science that you'd like to see about randomized controlled trials for that exact product to prove that it works, but also how the science can get distorted and misled either intentionally where you're sort of cherry picking this particular papers or something that you did in a petri dish or even unintentionally. We've also said, like scientists can also just make mistakes. I'd love to bring this back around to the beginning about pills and supplements and now say, okay, given all of this, what really should be the advice? And I'd love to start with the vitamins and talk about what should we all be taking.

[C]

So what we should be taking is the time to make sure we have a relatively balanced diet if we have the luxury and the ability to afford it. And really, in my not very humble opinion, that is reliably eating food that looks more like it looked when it either was harvested or alive, swimming in the ocean, et cetera. So less processed, more sort of healthy and fresh. But that's easier said than done. And for people who are unable to access that, then to do the best they can with that. As far as taking supplements is concerned, unless you have an identified risk or deficiency that your doctor has recommended that you take a supplement, there is really no benefit to any of these with a couple of minor exceptions. And so for the general healthy population, the recommendation is don't waste your money and that what you're doing may in fact have risk that has not been identified because these have not been studied properly in long term studies such as I've mentioned with the vitamin E and, and selenium.

[B]

It's a very powerful statement.

[A]

I'd love to run through a few.

[B]

Specific vitamins so that people I think will say, yeah, yeah, yeah, yeah, but I know I need to take vitamin C because everyone knows that that's really good for you. Come on, David, surely that's an exception, isn't it?

[C]

No, the studies in vitamin C have shown really no salutary benefit for again for healthy people who don't have a deficiency, with one minor exception, and that is in performance athletes. A couple of studies have shown that, that intense skiers and marathon runners had fewer colds if they took vitamin C, which is a thorn in my side. But the data is the data and those were randomized trials. So if you are one of those in one of those groups and want to decrease your frequency of common cold, then perhaps vitamin C is something that you should consider, but at much lower doses than what are usually prescribed.

[B]

And if I'm going to the gym a few times a week, don't I get to count? Like.

[C]

Yeah. No.

[B]

Okay, so you think really of no benefit?

[C]

Really of no benefit.

[B]

What about vitamin D?

[C]

Oh boy. So vitamin D is a real headache for those of us who want to adhere to science on this. The story of vitamin D is actually kind of interesting in that some years ago a laboratory arbitrarily decided to label the a certain range of vitamin D level as insufficient based on very weak evidence. But they labeled it insufficient. So now all of a sudden 50% of the population has vitamin D insufficiency and it created a billions of dollar industry in vitamin D testing. So that's piece number one in the randomized controlled trials of the general population. Vitamin D has not shown to have much benefit. There have been some studies in older folks that showed maybe a slight decrease in the incidence of falls, but really not anything. That's enough of a bang for your buck that I would recommend taking it. And of course all of these have the potential for side effects and deleterious effects.

[B]

So just to confirm, David, you are not taking vitamin D, I am not taking vitamin D. And you think that at least for the healthy population, again, even if the lab test says that they're insufficient in vitamin D, that you don't need to go and take this right now.

[C]

This is debated hotly in the very lowest of those levels as to whether or not this really constitutes a deficiency or not. But without really good study, I really can't support that. When it's just a matter of opinion. People like to butt heads. When there's good strong evidence, there's no fight.

[B]

Is there any harm from taking mega doses of vitamin D?

[C]

Yes. Vitamin D at high doses can be very toxic. There are real, potentially even deadly consequences.

[B]

So I think again, particularly for people who might not have heard anyone talking about vitamins on previous podcasts, I think we'll be really shocked because I think they're generally presented as like something with no downside.

[C]

Sure.

[B]

Like, why not take it? It's sort of like insurance. You can't harm yourself. After all, they sell it. And it looks just like the things you get as medicines. And we know that's all supposed to be safe. So when could it be dangerous?

[C]

Vitamin D helps regulate your calcium uptake from the intestine, and if you save too much calcium, you can put deposits down in different tissues, the kidneys, the coronary arteries and so forth. And I should be very careful to say that there are some studies that associate the use of calcium supplementation with an increased incidence of coronary disease. But that's not a randomized trial and it's not a cause and effect relationship proven. But it worries me enough that without any good proof of benefit and with the potential for harm, this is just one example of how it might be harmful, that I would shy away from taking it.

[A]

Do you know someone who's confused about which vitamins to take? Share this episode with them now. It might just help them rethink their routine, improve their health and save them money. I'm sure they'll thank you.

[B]

So, David, I think you're caring for critically ill patients who are relying on life saving nutrition support when you're with patients, is that right?

[C]

That's correct.

[B]

So in those cases, are there a lot of sort of exceptions to the skepticism that you're talking about? You know, do you, in those cases suddenly, are you giving them all of these different vitamins?

[C]

No, no, no. And in that situation, there are many examples of how we've been misled. Vitamin D being a big one. Vitamin D is a fat, so it doesn't just float around in the bloodstream. It has to be adhered to a protein. And that protein level drops during illness. So the vitamin D level drops during illness. And so of course, because there's an association between vitamin D levels and survival, everybody promoted vitamin D supplementation in the icu and when the randomized trials were done, they showed no benefit. Now, if you go to the search engine that we use to find articles, it's called PubMed, you will find about 400 such studies in critically ill patients looking at the correlation between vitamin D levels and survival and then analyses and summaries and so forth of that phenomenon. And there are four or five randomized controlled trials, but those all showed no benefit. I received a call in April of 2000 when Covid was just starting to take off. I got a call from a journalist and said, did you see this article? Now, at the time, the big journals had made it possible for you to submit an article and have it be viewed publicly, clearly labeled as not reviewed, but before peer review, so that people could get a sense of what was going on, scientists could get a sense of what was going on and do something about it. And somebody had done this with an article that correlated historic blood levels of vitamin D with some Covid outcome. I don't remember what it was, whether it was survival or incidence, it doesn't matter. And the authors had concluded that vitamin D might improve Covid. Well, I explained to the journalist that this was very derivative. It wasn't direct evidence, it was very poor quality evidence. So it really didn't amount to something that was actionable, except perhaps to design a study, a proper study. He said thank you and wrote a responsible piece on this. But it appeared on the national news two nights later. I've been tracking this and now we're over 2000 papers discussing the relationship between vitamin D and Covid. And the four or five randomized controlled trials that were done showed no benefit whatsoever. So this is the kind of thing that happens even in medicine when we mislead ourselves about vitamins and so forth. We would love for vitamins to be something that would have a benefit to our patients, something magical that we hadn't discovered or. But mostly we've failed in that. Another example in the critically ill patients was vitamin C. There was a lot of interest in using vitamin C in large doses in very, very critically ill patients based on some observations. And that's how it always starts though I got to stop and say it always starts with good observations. But the observations are what we call hypothesis generating. They give us a question that we want to study. So anyway, vitamin C associated with outcomes in the seriously critically ill patients, a lot of interest in that. And randomized trials failed to show enough of a benefit and potential harm so that we don't do that.

[B]

I'm a little shocked by all of that, to be honest, because I would have expected that, okay, sort of healthy people able to eat a healthy diet, you know, vitamins don't help. But I would have thought people who are like really, really sick in intensive care would have been the sorts of group who would benefit from something like this because, you know, they're not going to be like eating a nice, like plant heavy diet and all the rest, I mean, we all know what hospital food is like. So I'm actually really shocked that you're saying, even in that extreme, a situation where it sounds like there've been a lot of randomized controlled trials, there's no benefit.

[C]

That's correct.

[B]

So where does that leave us as we go into old age? Because I have also heard people say, well, you know, the evidence against vitamins is not so strong as we're, you know, we're healthy. But, you know, in the same way that we believe in certain vitamins when you're pregnant and there's strong evidence, like, it seems like it makes sense to move to sort of like a multivitamin once you're, you know, 65 plus or something like that. And I'm looking at you now thinking that you're going to tell me something really unexpected about this.

[C]

Yeah. You know, again, there is some suggestive evidence that people who take multivitamins may have a decreased incidence of dementia and some other things, but it's still very weak. And given the frequency over my career with which I have been surprised by the harmful effect of something, I really just can't get behind the idea of wholesale supplementation simply because you're over a certain age.

[B]

And is that because you're cautious that potentially we're like, taking in these individual chemicals, like, more than we would do through our natural food, and therefore it potentially has a harmful effect rather than it just being a waste of money?

[C]

That would be. Well, both. And that would be one of many different possible reasons. But as I said, biology is complicated, and we don't know until we have really good studies done. And it's never quite made sense to me that people don't think of vitamins taken for health benefit in the same way they would think about medications. If you're taking them for salutary health benefit, why would you not want to make sure that they'd been properly tested? And the answer, I think, goes back to people wanting control of their health outcomes, not trusting the experts and so forth. And I understand that, but I wish we could get people to think about this in a different way.

[B]

I think also a lot of people listening to this are gonna be really surprised that it isn't more tested, that there aren't more, like, proper randomized control trials for each of these things, proving that it works because they are sold to look like medicines. The marketing around them, let's say, you know, even maybe the influencers behind them, like this all feels like they've done some real tests And I think you're saying there's a mix between they haven't or even where they've been doing these, like some of these vitamins you're talking about, like the results have been much less compelling than I would have expected.

[C]

Right. I also just want to point out that these studies are expensive to do. To do a 30,000 person 10 year study costs millions of dollars. And you know, the vitamin supplement industry doesn't have, I don't think, the kinds of money that, I don't know, maybe they do that the drug industry has to support these kinds of studies. And the government has not been forthcoming, the US Government in supporting these kinds of studies to a large extent. And I think that it's likely that these studies would fail to show benefit enough that the industry is not that interested in doing them. I don't know that for sure, but it's just my supposition.

[B]

So, David, what about probiotics?

[C]

Probiotics are bacteria that are given for health benefit. And it's a very funny term because most of the probiotics are not normal inhabitants of the intestine. And there have been decades and decades of looking at supplementing these bacteria to look for a health benefit. And there have been some small ones. There were some studies that said that it might decrease the incidence of ear infections in kids, you know, some such. But these are essentially yogurt bugs for the most part. There's some yeasts and some others that are not, but they're not normal inhabitants of the intestine. Therefore they don't survive much past the stomach. So to expect a salutary benefit from any of them seems to me far fetched. That's changing. There are some bugs that normally inhabit the intestine that people are experimenting with, but that's still in experimental stages. And these have been around for 30, 40, 50 years on the market. I think your listeners would also be interested in hearing about some of the other terminology around this. You're hearing a lot these days about prebiotics. A prebiotic is simply something that the bacteria eats and in most cases it's a fiber that's fermented by the bacteria. Now there are a lot of reasons why that might have a salutary health benefit in that the breakdown products of fiber fermentation include substances that are food for the colon. But the idea that giving more of this as a positive benefit has not been proven. And in fact some of the studies that have been done have been really disappointing and they're hard to do because the Main thing that we're looking at are things like developing colon cancer. But a prebiotic is just a fiber. I will also say that there are many fibers on the market that are fermentation resistant and that's because they're used for constipation, because they pull water into the intestine. You don't want a lot of fermentation if you're giving a lot of fiber because the other byproduct is gas. So one of the side effects of taking these is a lot of bloating and gas. So with the good comes the bad. Then the newest and latest, which the term has been around forever, but there are some products that are being sold as synbiotics. Synbiotics and syn, meaning together, just means a prebiotic and a probiotic put together in a pill and given to you.

[B]

So you are, I think it's fair to say, one of the world's top physician nutrition practitioners. Right. You're combining this together with people who are really sick. So this really matters. Having sort of laid waste to the supplement landscape. What is the best way to eat for our health?

[C]

Well, as I said, I think first of all, we're really unsure of our recommendations. It's important to understand that because our recommendations are not based on long term randomized trials. And I don't know that we'll ever get those in actual diet because they're very difficult to do. Imagine being told you have to eat a certain way for a decade. It's less impossible than we had thought previously. People are getting much better at behavior change interventions. But suffice it to say that those kinds of studies are extremely difficult to do at best. And so we don't have good randomized trials over long periods of time. Yet now there are some shorter term randomized trial where for instance, the experimenter provides the diet. But those are again, expensive and take a long time to really figure it out. And then we have to look at the heterogeneity, the differences between people. It may be that you and I would have better health benefits from different diets, that I might be healthier in the long run with a high fat diet, where you might be healthier in the long run with a low fiber diet. It's the ability to pull apart the biology and understand this in its infancy. Being able to personalize nutrition, which is really being promoted. I don't think it's ready for prime time.

[B]

And if you were gonna give the core tenets, it's only what we have, right? We have to give advice Based upon the data that we have, what would be the key things that you would be advising someone for eating for their health.

[C]

So for people who can afford it, a diet that's got a lot of things that look more like what it looked like when it was harvested or when it was on the hoof, the wing, or in the water to avoid the heavily processed foods and really to shift away from meat and animal products. But I'm not sure that completely doing away with them in the diet is necessarily the right thing to do. For instance, speaking of B12, there is no such thing as a vegan B12. It's all from animal sources. And the way that they sell vegan B12 is by taking B12 that's from an animal and growing it in a yeast that takes it up and that now it's yeast B12, but the yeast didn't make it.

[B]

One thing that comes up a lot on this podcast from other scientists that I haven't heard you mention is this idea that for most of us in the west, we're actually living with a deficiency of fiber and a deficiency of sort of a diversity of plants.

[C]

Yes.

[B]

What's your view on that?

[C]

I am of the opinion that it's probably real based on the evidence that's available. I want to make sure that I say this in that way because it could turn out to be that eating nothing but Fritos is the healthiest diet in the world. But I doubt it. I'm saying that it is my current opinion that that seems to be the way we're headed. If we were able to ever do the kind of study that we'd have to do, there's enough suggestive evidence. Again, it's suggestive. And smaller studies that have been done that use things that are sort of waypoints, things that identify risk. Those studies are suggestive enough for me to get behind this, enough to say that if you want recommendations from me, I don't know what I'm talking about. Science doesn't really know what it's talking about. But as best we can tell, this is probably the way to go.

[B]

And you say that with that note of caution. Cause you feel that unless you've been able to do this randomized control trial, so you've randomly associated people between eating beef burgers and bacon on one side and plants and olive oil on the other hand, you haven't got this highest level of test. And so you feel that you can't have that level of conviction. You'd like to have about this choice that's well said.

[C]

Yeah. I don't have the conviction because of the lack of good evidence.

[B]

So final question, David.

[C]

Sure.

[B]

If you were going to say one thing to people listening to say this is what I would suggest you do tomorrow, what would it be?

[C]

It would be look at your diet and don't go to the vitamin store.

[B]

Brilliant. Thank you very much.

[A]

I'd like to do a quick summary.

[B]

Of what we've covered. And I mean the thing that really sticks in my mind is that there is no benefit from vitamins, even from people who are so sick they're in intensive care and they're like hooked up to things and they are definitely not able to eat a healthy diet. And I'm shocked by that because I saw like, well, surely they would be benefiting from vitamins.

[C]

Well, in truth, most of them at least there's an attempt to feed them with food, you know, with a tube with a product that has vitamins and minerals in it, but to varying success depending on how sick they are.

[B]

It's quite striking to me. And then you said more broadly that we've ended up in a situation particularly bad here in the U.S. but you know, is replicated I think around the world where the level of regulation around supplements is very low. They're able to make a lot of scientific claims, but ones that you wouldn't be able to make with medicines. Most of the time they haven't run some sort of randomized control trial on their product. Which you've said over and over again is like this is the high bar of whether or not to really believe in a result.

[C]

Correct.

[B]

And instead they've done some amazing jobs about running advertising campaigns either to allow regulation in the first place in the US or just to support their products and to convince us based upon often much looser claims, that this works. And then I think we talked about some like specific vitamins cause I was like sure, sure, sure. But come on, vitamin C. And you were like no, unless you're a downhill skier or run marathons. And for vitamin D, much to my surprise, you said again there's a story about a lab creating like a range that says half of the population in the US was deficient and that wasn't based on any real science and that they've now done all of these follow up studies and again you can have much lower levels of vitamin D and it didn't matter. And they looked at this vitamin D supplementation and again you've said in the vast majority of cases it doesn't seem to have had an impact. So for you, don't take vitamin D. And actually if you take super doses of it, you said you could actually be risky.

[C]

Well, don't take it unless you've discussed that with a doctor. There are guidelines as to the levels and the risk factors associated with low vitamin D levels. So that population has been sort of addressed in medical guidelines.

[B]

So make sure that you follow what your doctor says. And as I went through asking you about this, you're like, well, what about when you're older? And you're like, no. Also, you don't really see the evidence. So I think what's amazing is with all of this research you've done, you sort of come out very skeptical about these traditional vitamins. And I think what you've also said is the current generation of probiotics that are out there are really based upon things that you could happen to grow easily rather than anything that lives inside your gut. So fundamentally, you need to think about the food that you're eating and how do you get, you know, the right sort of food, which you describe as, you know, avoiding processed food, you know, getting things much closer to whole food and plants, the sort of things that come up everywhere. But finished, I think, with really interesting challenge, which is you've changed your mind repeatedly. You feel like you've made advice like low fat in the past that now you know is wrong. And it makes you personally feel much more cautious about giving really strong advice because you recognize that you can't do those sorts of randomized control trials on an entire diet. And so ultimately it's always going to be this sort of blend of data. David, it was such a pleasure.

[C]

A pleasure for me too. I really enjoyed it.

[A]

I'll leave you with one final thought. What if there was one simple habit that when repeated, could change how you feel for the better? I'd like to tell you about something that I do daily for my own health. It's called Daily 30, the gut supplement developed by our scientists here at Zoe. Daily 30 is made of over 30 hand picked plants, including seaweed, fungi and different types of fiber. It's a source of plant protein, omega 3 and vital minerals. You simply add a scoop to any meal once a day to support your health and increase the plant diversity in your diet. And unlike synthetic supplements, Daily 30 actually tastes great. It's designed to be enjoyed because when a habit brings you joy, you're far more likely to stick with it. So next time you feel like your plate is missing extra plants, do yourself a favor. Try Daily 30 it's a delicious and healthy habit that you'll feel good about, and one that your gut will definitely thank you for. By the way, whenever we talk about Daily 30 as a good source of fiber, we're required to say that it contains 4 grams of total fat per serving. Obviously, that's all amazing healthy fats from plants, so order yours [e-mail] daily 30. See you next time.