Chasing Life: Why Seeing Blood Makes People Faint
Podcast: Chasing Life
Host: Dr. Sanjay Gupta (CNN Podcasts)
Episode Date: October 28, 2025
Episode Overview
This episode, timed for Halloween, addresses why some people have such strong aversions to blood that they faint at the mere sight of it. Dr. Sanjay Gupta answers a listener's question by breaking down the neurobiology of blood-injury-injection phobia (BII), including its unique physiological response and potential evolutionary roots. The episode also addresses the safety of artificial sweeteners, featuring commentary from an expert in health policy. Throughout, Dr. Gupta emphasizes practical advice, evidence-based insights, and the importance of asking questions about our health.
Key Discussion Points & Insights
1. Why Do Some People Faint at the Sight of Blood?
- Listener Question from Heidi:
"What happens in the brain to make some people fear blood and others don't?"
(00:29)
Dr. Gupta’s Breakdown (02:33)
-
Hemophobia Defined:
- Extreme fear of blood, also called hemophobia, is part of blood-injury-injection phobia (BII), affecting about 3–4% of people.
- BII encompasses fear of blood, needles, injuries, and medical procedures.
-
Unique Physiological Phases:
- Most phobias (e.g., spiders): Trigger the sympathetic "fight or flight" response—increased heart rate and blood pressure.
- BII response:
- Phase 1: Brief hyperarousal (heart rate and blood pressure spike).
- Phase 2: Dramatic crash in both (vasovagal response).
- This sudden drop decreases blood flow to the brain, causing fainting.
- Controlled by overstimulation of the vagus nerve.
"A BII response, on the other hand, sort of seems to have two phases. First, a short burst of hyperarousal... followed by a dramatic crash ... That is why people faint, because there is a sudden decrease in blood flow to the brain."
— Dr. Gupta (03:20) -
Brain Differences:
- People with BII:
- More activity in vision and attention parts of the brain (thalamus, occipital temporal cortex).
- Less amygdala (fear/emotion center) activity compared to other phobias.
- 2009 study: BII phobics’ neural patterns differ significantly from spider phobics.
- People with BII:
-
Why Some People and Not Others?
- Genetics may play a role.
- Higher prevalence among women noted in some studies.
- Possible evolutionary purpose: “Fainting and then falling horizontally is a way to restore blood flow to the brain in case of major blood loss.” (04:33)
Practical Coping Tip: The Applied Tension Technique
- How to Use:
- Sit comfortably.
- Tense muscles in arms, legs, and trunk for ~10 seconds (until your head feels slightly warm).
- Relax for 20–30 seconds.
- Repeat five times.
- Purpose: Raises blood pressure a bit to prevent fainting.
- Counter-intuitive Advice: Don’t simply try to relax—too much relaxation might lower blood pressure further and increase fainting risk (05:32).
"While the goal of many phobia-related therapies is to help you relax, that's not necessarily the goal here... Feeling too relaxed might mean your blood pressure is even lower..."
— Dr. Gupta (05:45)
2. Artificial Sweeteners: Are They Safe? (07:39)
- Listener Question from Ashish:
“How safe are the sugar substitutes...Aspartame, or various other names? If consumed in moderation, do they have any side effects?”
(07:39)
Dr. Gupta’s Overview (08:05)
-
Types of Sweeteners:
- Synthetic (aspartame, sucralose, saccharin).
- “Natural” (stevia from stevia plant).
- All FDA-approved.
-
Pros:
- Low/no calories
- Do not cause tooth decay.
- Usually do not raise blood sugar—useful for people with diabetes or weight loss goals.
"They are low calorie or no calorie, they do not cause tooth decay like sugar can, and they usually don't raise blood sugar levels..."
— Dr. Gupta (08:14)
Expert Perspective: Dr. Laura Schmidt (09:13)
-
American vs. Precautionary Principle:
- U.S. often tests product safety after public exposure ("put it in the cereal and wait to see if it's safe").
- Cautions that long-term safety isn't always assessed before products go to market.
-
Potential Drawbacks & Debates:
- Some major studies show negative effects on the gut microbiome.
- Research links consumption to weight gain/obesity—though debate exists over causation.
- Multiple studies suggesting risks mean “we ought to be thinking twice about it.” (10:32)
“There are some very influential papers...that show very negative effects on the gut microbiome... consumption ... actually increases your weight, can produce obesity.”
— Dr. Laura Schmidt (10:06)
Dr. Gupta’s Takeaway (10:42)
- Helpful for “soda addictions” to quit sugary sodas.
- If you don’t have diabetes, best to avoid artificial sweeteners.
- Moderation if you use them.
- Healthiest sweet snack? Whole fruit—enjoy it slowly and mindfully.
“If you can avoid artificial sweeteners, it's probably a good idea... the healthiest snack option if you're looking for something sweet is whole food, like a fruit. Try it. Eat it slowly.”
— Dr. Gupta (11:12)
Notable Quotes & Memorable Moments
-
On the evolutionary theory behind fainting:
"Fainting and then falling horizontally is a way to restore blood flow to the brain in case of major blood loss. I thought that was kind of fascinating."
— Dr. Gupta (04:33) -
On therapy for hemophobia:
"While the goal of many phobia related therapies is to help you relax, that's not necessarily the goal here. Right, because feeling too relaxed might mean that your blood pressure is even lower..."
— Dr. Gupta (05:45) -
On American food safety standards:
"In America, we don't follow the precautionary principle... Instead, we flip it around and we say, put it in the cereal and wait to see if it's safe."
— Dr. Laura Schmidt (09:21) -
On choosing natural sweetness:
"Eat it slowly. Taste every molecule of it. It's pretty good."
— Dr. Gupta (11:14)
Important Segment Timestamps
- What makes some people fear blood? (02:33–06:27)
- How to prevent fainting at sight of blood (05:18–05:55)
- Artificial sweeteners explained (08:05–09:12)
- Expert on food chemicals – Laura Schmidt (09:13–10:42)
- Dr. Gupta's final take & practical advice (10:42–11:30)
Episode Tone & Closing Thoughts
The episode is upbeat, scientific, and reassuring, reflecting Dr. Gupta's curiosity and commitment to practical, evidence-based health guidance. He encourages listeners to keep asking questions about health—as “part of chasing life.” His advice is both compassionate and actionable, demystifying complex topics with clarity and warmth.
For those who haven’t listened, this episode offers an accessible explanation of why some of us faint at the sight of blood and provides valuable tips for managing both blood-related fears and choices about artificial sweeteners. The practical advice and expert insights make it a worthwhile listen—especially before Halloween!