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Be honest—have you ever rescued a French fry from the floor? In this bite-size myth episode, I test the famous “5-second rule.” I walk through what actually transfers to your food (fast), when that matters, and why a little microbial exposure isn’t always the villain—while drawing a hard line for high-risk settings and situations.

Key Topics & Takeaways

• The verdict meter: The 5-second rule is false—bacteria can transfer in <1 second. In a Rutgers lab study, juicy foods like watermelon picked up the most, gummies the least; tile/steel transferred more than carpet (Applied and Environmental Microbiology / PubMed
  ).
• Foodborne illness is common: ~48M illnesses/year in the U.S., ~128k hospitalizations, ~3k deaths. Usual suspects include Salmonella, E. coli, Campylobacter, Listeria, and norovirus. Symptoms are typically GI, but severe cases occur—especially in the very young, elderly, pregnant, or immunocompromised (CDC overview
  ).
• Context matters: Moisture and surface trump “time.” High-moisture foods collect more microbes; visibly dirty or high-traffic floors (think convenience stores) raise risk—regardless of seconds.
• When to skip the floor food—no debate: If you’re immunocompromised, pregnant, very young/elderly, or you’re in a hospital/clinical setting, don’t eat it. Full stop.
• Nuance: Are microbes always bad? Early, diverse exposure to benign environmental microbes associates with more resilient immunity. Farm-exposed kids had lower asthma/atopy rates (≈20–40%) versus city peers (NEJM
  ). Greening urban daycare yards (adding soil/plant matter) increased skin/gut microbial diversity and shifted immune markers in a favorable direction (Science Advances
  ). This doesn’t mean “eat off the floor”—it means the bigger story is about exposure diversity and context.
• My practice: At home, I don’t stress over a quick drop on a clean surface; out in public or medical settings, I pass.

Bottom Line
Microbes hop on fast; the “rule” doesn’t save you. But danger depends on what fell, where, and who is eating it. Be smart, especially if you or your environment are higher risk.

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Summary: I unpack why medicine sometimes reverses course—and how you can tell sound evidence from shiny anecdotes—with physician-author Dr. Adam Cifu of the University of Chicago and co-author of Ending Medical Reversal
.

Key topics & takeaways

• Why medicine “flips”: Plausible theories + observational data → premature guidelines; true answers require randomized trials. Classic examples: menopausal hormone therapy, early peanut avoidance, and stents for stable angina (LEAP trial
  , COURAGE
  
  
• Open-minded skepticism: Ask, “What’s the human outcomes evidence?” Cool mechanisms and moving testimonials aren’t proof.
• Hype outside the clinic: Mitochondria “rechargers,” microbiome panaceas, and biological age tests are intriguing—but not ready for prime time.
• Nutrition sanity: For supplement evidence summaries, I like Examine
  .
• When AI helps (and when it doesn’t): Tools can orient you to established topics; they’re weaker on breaking studies. Look for linked primary sources.
• N-of-1 experiments: When evidence is uncertain and the outcome is measurable (sleep, blood pressure, pain), test on yourself—track a baseline, try the change, measure again, and, if possible, stop-start to confirm. Use symptom diaries, validated scales, or wearables.
• Humility is a signal: Trust sources that sometimes conclude “we don’t know.” I often check Cochrane Reviews
  for balanced syntheses.

About my guest
Adam Cifu, MD is a professor of medicine at the University of Chicago, author of 140+ peer-reviewed papers, and co-author of Ending Medical Reversal. He writes at Sensible Medicine.

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If this episode helped you think more clearly about health claims, share it with a friend and leave a quick review on Apple or Spotify. For my newsletter on practical, evidence-supported longevity, visit DrBobbyLiveLongAndWell.com
.

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I unpack what “ultra-processed” really means, why these foods are so easy to overeat, what the best evidence shows (including metabolic-ward studies), and how I personally navigate them without fear or perfectionism.

Key topics & evidence (in plain English):

• What counts as “ultra-processed”? I walk through the NOVA system—useful, not perfect—and where borderline items (frozen meals, boxed mixes) fit. See an overview of NOVA classifications here
  .
• How we got here: post-WWII abundance of refined flour, cheap sugars, oils, and a cultural push for convenience—now ~60% of the U.S. diet comes from UPFs (study
  ).
• Additives: stabilizers, emulsifiers, preservatives, and colors are generally recognized as safe (GRAS). I explain why, on their own, they’re probably not the main health issue.
• The bigger problem: UPFs are energy-dense, engineered for bliss (fat/sugar/salt + perfect texture), and easy to eat quickly—driving higher calorie intake.
  • Metabolic-ward crossover trial: +~508 kcal/day when participants ate UPFs vs minimally processed (Cell 2019
  ).
  • Overweight adults in a crossover design: +~814 kcal/day on the UPF week (PubMed
  ).
  • Another recent crossover RCT reports ~300 kcal/day higher on UPFs (Nature Medicine 2025
  ).

What I recommend (and what I do):

• Prioritize whole foods most of the time; shop the perimeter; cook when you can. Canned tomatoes/beans and frozen fruits/peas are fine helpers.
• If weight, diabetes, or blood pressure are concerns, be extra cautious with UPFs—they’re designed to be irresistible and calorie-dense.
• Moderation wins: I enjoy favorites (yes, even boxed mac ’n’ cheese and crunchy peanut butter) without letting them dominate my plate.

Takeaways you can use today:

1. Build meals around minimally processed proteins, veggies, fruits, and beans; let convenience items support—not star—in your diet.
2. Watch “calorie-dense + easy to overeat” combos (chips, sweets, fast food). If you have them, portion once, then put the package away.
3. If symptoms or inflammation are puzzling you, try a short UPF-light experiment (2–4 weeks) and see how you feel.

If this episode helped, please follow and leave a quick review—and share it with a friend who’s curious about UPFs. For my newsletter and resources, visit drbobbylivelongandwell.com.