Ready to begin or deepen your meditation practice? Join Dan Harris and world-class meditation teachers on the 10% with Dan Harris app here: https://app.danharris.com/membership Half of American adults are reportedly low on magnesium. Forty percent are vitamin D deficient. And the supplement industry happily wants to sell you the fix — to the tune of a quarter-trillion dollars a year, in a market that's almost entirely unregulated. So how do you know what actually works, what's a waste of money, and what might be quietly hurting you? Dr. Mahtab Jafari is a Professor of Pharmaceutical Sciences and Ecology and Evolutionary Biology at UC Irvine, where she's spent three decades researching the safe use of dietary supplements and testing botanical extracts in her own lab. Her new book, "The Truth About Dietary Supplements: An Evidence-Based Guide to a Safer Medicine Cabinet," is exactly what it sounds like. In this episode we talk about: – Why nearly every claim on the bottle of your supplement is, technically, unverified – The exact blood tests to ask your doctor for before buying anything – What's the deal with vitamin D, B12, magnesium, and the multivitamin you've been popping for years – Whether omega-3s actually help with depression (and what the studies miss) – The recent melatonin study that should make daily users pause – Why "green powders" like AG1 can't replace a salad – Creatine, peptides, protein powders — the hype vs. the data – Why you should bring your supplements to your next doctor's visit Subscribe to watch more 10% Happier videos: https://www.youtube.com/tenpercenthappier Follow Dan Harris on Social Media: https://www.instagram.com/danharris/ https://www.tiktok.com/@danbharris https://www.facebook.com/DanHarrisABC https://twitter.com/danbharris https://www.linkedin.com/in/dan-harris-91ba5716b/ 0:00:00 Why supplements are a wild west 0:03:00 The $275 billion question 0:06:00 What "unregulated" actually means 0:13:00 How to vet a supplement company (NSF, USP, ConsumerLab) 0:15:00 Vitamin B12 — do you actually need it? 0:21:00 The blood tests to ask for at your next checkup 0:29:00 Vitamin D — the most controversial vitamin 0:32:00 Vitamin C, Airborne, and the cold-and-flu myth 0:37:00 The truth about multivitamins (and a study that should give you pause) 0:40:00 Calcium and the kidney problem nobody mentions 0:42:00 Magnesium for sleep — what one good 2025 study found 0:47:00 Melatonin's hidden risk 0:51:00 Omega-3s, depression, and brain health 0:57:00 St. John's wort — why you need a doctor to prescribe it 1:02:00 AG1 and the green-powder pitch 1:05:00 Protein powder, heavy metals, and the 47% problem 1:08:00 Creatine — the case for it 1:11:00 Peptides, collagen, and what the studies don't show 1:12:00 Probiotics — when they help and when they don't #10PercentHappier #Supplements #healthscience Sponsors: BetterHelp: May is Mental Health Awareness Month — a reminder that whatever you're dealing with, you don't have to deal with it alone. Sign up and get 10% off at https://www.betterhelp.com/happier Fast Growing Trees: America's largest online nursery, with thousands of trees and plants guaranteed to arrive healthy. Listeners get an additional 20% off their first purchase with code HAPPIER at https://www.fastgrowingtrees.com Warby Parker: Buy one prescription pair and get 20% off any additional prescription pairs at https://www.warbyparker.com/happier