Podcast Summary: What's That Rash? – "Can flossing benefit more than your teeth?"

ABC News | February 17, 2026
Episode Focus:
This episode investigates whether flossing your teeth can benefit more than just oral health and reduce your risk for heart disease, stroke, or Alzheimer's disease. Hosts Norman Swan and Tegan Taylor address listener Carrie’s question about the broader health impacts of flossing, and offer evidence-based insights on new dental gadgets like infrared toothbrushes.

Main Theme

The discussion centers on the commonly-circulated claims that oral health habits like flossing may prevent serious health issues beyond the mouth, like heart disease and Alzheimer's. The hosts assess scientific evidence behind these headlines and clarify what flossing is actually proven to do.

Key Discussion Points & Insights

Opening & Listener Question

• Teeth Cleaning Routines:
  • Norman shares his meticulous dental habits, including brushing and using both floss and interdental brushes to tackle food particles in his crowded mouth.
    • "I've got a crowded mouth... so interdenting gets rid of stuff that is in between your teeth, and flossing will get rid of anything that's caught in the tight spaces..." (03:00, Norman)
  • Tegan quips about less fastidious habits and lunch leftovers:
    • "If this microphone could talk, it would tell you what I had for lunch." (00:53, Tegan)
• Carrie’s Email:
  • Asks if flossing really protects against heart disease, stroke, or Alzheimer’s, and whether infrared toothbrushes (promoted widely online) are beneficial or just marketing hype. (01:46)

Oral Health 101

• What’s Happening in Your Mouth:
  • The hosts describe the bacterial biofilm in the mouth (plaque), culprit in tooth decay and gum disease, and explain why oral hygiene matters.
    • "Our mouths are innately disgusting, full of bacteria... the sticky kind of biofilm." (04:09, Tegan)
• Why Dentists Prioritize Flossing:
  • Dentists view flossing as key for oral prevention, even if the broader health links are less certain.
    • "...dentists have been much more focused on prevention than many doctors... They believe strongly that flossing and, you know, inter dental work is really important for your oral health and some would say your physical health, which is really what this question's all about." (05:17, Norman)
• History of Floss:
  • The first mention of dental floss dates back to Levi Spear Palmley in 1819, who advised silk thread for cleaning between teeth. Commercial floss appeared in 1882.
    • "In 1819, he recommended running a waxed silk thread through the interstices of the teeth... which is the real source of disease." (06:37, Tegan)

The Oral-Systemic Health Link

• Biological Rationale:
  • Gum inflammation (gingivitis, periodontitis) caused by bacteria is associated with heart disease and possibly dementia.
    • Inflammation could trigger immune responses leading to arterial plaque (atherosclerosis) or allow bacteria to escape into the bloodstream and cause harm.
    • One notable bacteria, Porphyromonas gingivalis, is implicated in Alzheimer’s through its impact on tau and beta-amyloid proteins:
      • "Fragments of this bug get into the brain... can induce the two damaging processes that are part of Alzheimer's disease..." (09:15, Norman)
• Epidemiological Evidence:
  • Studies show association, but not causation. Socioeconomic status, smoking, and general health behaviors confound findings.
    • "Correlation does not equal causation. And there might be other things at play." (10:59, Tegan)
  • Once studies adjust for factors like age and lifestyle, the association between poor oral health and heart disease diminishes.
    • "Once they adjusted for age and other factors... that association kind of disappeared." (11:46, Tegan)
• Clinical Trials Challenge:
  • Impossible to blind participants in flossing studies; hard to prove direct links.

What Flossing Is Proven to Do

• Clear Benefits:
  • Flossing and interdental cleaning help prevent plaque, dental calculus, and tooth decay, and help people retain more of their natural teeth.
    • "If you make no more than that, it's good for your oral health. If that's all that it does, that's pretty good." (12:16, Norman)
  • Frequent flossers have lower DMF (Decayed, Missing, Filled teeth) scores.
    • "People who floss have more of their native teeth than people who don't floss." (12:16, Norman)
• Bonus Effects?:
  • Even if the protective effect for heart and brain is unproven, improving your oral health is already worthwhile.
    • "You're going to make dentists work easier and preserve your teeth for longer. And if it has an effect on your brain and your heart, that's an extra bonus." (13:35, Norman)

Infrared Toothbrush Gadgets

• Evidence & Value:
  • Limited, poorly conducted research—often industry-funded—makes current claims unreliable.
  • Dentists use controlled lasers/infrared for specific treatments, but home gadgets are unproven, may be expensive, and effects are unknown.
    • "We really don't know the effect of the infrared toothbrushes.... Why wouldn't they? Because they're probably sponsored by the manufacturer..." (14:23, Norman)
    • "It'll harm your pocket. We just don't know." (15:11, Norman)
  • General principle: “If an intervention is strong enough to do you good, it's strong enough to do you harm.” (15:49, Norman)

Other Oral Health Habits

• Is Too Much Harmful?:
  • Overbrushing after meals could damage enamel—wait a while post-meal before brushing or flossing.
    • "You don't want to brush your teeth immediately after a meal. You want to wait a while... " (15:56, Norman)
• Order of Flossing and Brushing:
  • No significant difference; both orders are fine as long as you do both.
    • "...doesn't make much difference either way whether you do first or second, as long as you do it." (16:57, Norman)
• Water Flossers:
  • Brief tease; to be addressed in a future episode.

Notable Quotes & Memorable Moments

• Norman's Flossing Philosophy:
  "Interdenting gets rid of stuff that is in between your teeth, and flossing will get rid of anything that's caught in the tight spaces between my teeth, which the interdent doesn't get to." (03:00, Norman)
• On Oral-Systemic Link:
  "There is an association between gum inflammation of various kinds and coronary heart disease. And some people believe there's an association with dementia as well." (08:36, Norman)
• On Caution with Health Claims:
  "Correlation does not equal causation. And there might be other things at play." (10:59, Tegan)
• Bottom Line on Home Gadgets:
  "It'll harm your pocket. We just don't know. I mean, here's the bottom line, which we've said often on what's that Rash. If an intervention is strong enough to do you good, it's strong enough to do you harm." (15:11, Norman)
• On Good Oral Health:
  "Oral health [is] enough for you, but there could be some potential bonus points in terms of your heart and brain health. Probably not. But why not? Just in case." (13:58, Tegan)

Timestamps for Key Segments

• Norman & Tegan Discuss Dental Routines: 00:36–01:31
• Carrie’s Listener Question Introduced: 01:46–02:31
• What Flossing & Interdental Cleaning Actually Are: 02:56–03:56
• Bacteria, Plaque, and Gum Disease Explained: 04:07–05:03
• History and Invention of Floss: 06:11–08:16
• How Gum Disease Might Affect Heart & Brain: 08:36–11:46
• Problems with Proving Causation: 11:46–12:16
• Definitive Benefits of Flossing: 12:16–13:35
• Infrared Toothbrushes Evidence & Warnings: 14:18–15:49
• Risks of Overbrushing/Flossing Timing: 15:56–16:33
• Order of Brushing & Flossing: 16:42–17:15

Conclusion / Key Takeaways

• Flossing is clearly beneficial for oral health (prevents decay/gum disease, helps keep your teeth).
• The evidence for flossing preventing heart disease, stroke, or Alzheimer’s is weak/unproven—links may be due to confounding lifestyle factors.
• Infrared toothbrushes and other new gadgets lack reliable evidence; stick to basics.
• No significant risk if you floss/brush twice daily and avoid brushing right after meals.
• Whether you floss first or brush first doesn’t matter—what matters is consistency.

This episode maintains a conversational, lightly humorous tone, but stays focused on science and practical advice. If you keep your teeth clean, you’re already ahead—even if your heart and brain don’t directly reap extra benefits. As Norman sums it up:
"If it has an effect on your brain and your heart, that's an extra bonus." (13:35)

For detailed answers to water flossers or to submit your own health queries, stay tuned or contact the show!