Which Supplements Actually Work? A Dietitian's Honest Audit
Updated: Sep 11
Americans spend more than $50 billion a year on dietary supplements. Most of it is wasted. Some of it is actively harmful. A small slice is genuinely useful — and the useful slice is rarely what's being marketed hardest.
Here's an honest audit of the supplements I see in clients' cabinets most often. I'm naming names. I am not paid by any of these companies.
Supplements with strong evidence (worth considering)
Creatine monohydrate. The most-studied sports supplement in existence, with evidence holding up across hundreds of trials. Increases strength and lean mass when paired with resistance training, and may have modest cognitive benefits — increasingly relevant for women in midlife. About five to ten cents a day. Buy the cheap version.
Vitamin D3, if you're deficient. Most New Yorkers, indoor workers, and people with darker skin run insufficient. A blood test (25-hydroxyvitamin D) tells you whether you need it. If you do, 1,000–2,000 IU daily is reasonable for most adults. Megadoses aren't better.
Omega-3s (EPA/DHA), if you don't eat fatty fish twice a week. Fish oil, or algae-based for vegetarians. Evidence for cardiovascular benefit in higher-risk populations and modest support for mood.
B12, if you're vegan, vegetarian, on metformin, on acid reflux medications, or over 60. Plant foods don't reliably provide it, and absorption decreases with age and certain medications. Real deficiency causes neurological harm.
Magnesium, sometimes. Common mild deficiency, decent evidence for sleep, muscle cramps, and constipation depending on the form. Glycinate or citrate for most uses.
Supplements with mixed evidence (situational)
Multivitamins. The classic. Evidence for general health benefits in well-fed adults is, charitably, weak. Not harmful for most people, but not the insurance policy it's marketed as. Better to fill specific gaps with specific nutrients.
Collagen peptides. Modest evidence for skin elasticity and joint comfort, mostly in older women. Your body breaks them into amino acids, so they're essentially expensive protein with marketing. If you enjoy the ritual, fine. If you're paying $40 a month hoping for younger skin, your money is better spent on sunscreen.
Probiotics. Strain-specific. The general "50 billion CFU" multi-strain isn't well supported. Specific products for specific conditions have legitimate evidence. The wellness-aisle version usually doesn't.
Ashwagandha. Some evidence for anxiety reduction. Quality varies wildly. Cycling on and off is reasonable rather than continuous use.
Supplements with weak or absent evidence
Greens powders. The category that has somehow convinced everyone that drinking neon-green dust is a substitute for vegetables. The amounts of any individual nutrient are small relative to actual food, the proprietary blend disclosure is bad, and a $90 monthly subscription buys you considerably less benefit than $90 of actual produce.
Apple cider vinegar capsules. Liquid ACV has very mild glycemic effects when taken with carb-heavy meals. The capsules are doing essentially nothing.
"Detox" supplements of any kind. Your liver and kidneys are detoxifying you constantly, for free. Anything sold as a detox is selling you an idea, not a function.
Most "hormone-balancing" supplements for women. Inositol has reasonable evidence for PCOS specifically. Most of the rest is preying on real symptoms with unsupported products.
Most "testosterone boosters" for men. A small number of ingredients have weak signal. The category as a whole is built on aspirational marketing.
Things that are actively concerning
Liver-toxic herbal blends that aren't well regulated. Very high-dose vitamin A or iron without testing. Anything marketed for rapid weight loss.
The supplement industry in the U.S. is regulated more like food than like medicine, and bad actors exploit that. Adverse events do happen.
How to decide what's actually in your cabinet
Ask three questions about anything you're taking. Is there a specific reason I started this? Does the evidence actually support that reason? Would I notice if I stopped?
If the answers are vague, vague, and probably not — you have your answer.
Bring your supplement list to your next physical. Ask your doctor or your dietitian (hi) to flag anything unnecessary or potentially interactive. Most of you will leave that conversation taking fewer pills and feeling no different. That's a win.
Frequently Asked Questions
Are greens powders worth it?
Generally no. The amounts of any individual nutrient are small relative to actual vegetables, the proprietary blend disclosures are usually poor, and the cost-to-benefit ratio is bad. If you struggle to eat vegetables, $90 a month of frozen vegetables and frozen fruit will outperform any greens powder.
Should everyone take a multivitamin?
No. The evidence for general multivitamin benefit in well-fed adults is weak. They're not harmful for most people, but they're not the insurance policy they're marketed as. Better to fill specific gaps with specific nutrients (after testing if appropriate).
Is collagen worth taking for skin and joints?
There's modest evidence for collagen peptides improving skin elasticity and joint comfort, especially in older women. Effects are typically small. Whether it's worth $40-80/month depends on your budget and how strongly you respond. Sunscreen will do more for your skin than collagen will.
What supplements should women take daily?
It depends entirely on the woman. For many: a vitamin D supplement (if levels are low), omega-3s (if not eating fatty fish twice weekly), and B12 (if vegetarian, over 60, or on certain medications). Add iron only if iron-deficient on a blood test. There's no universal stack.
Is creatine safe for women?
Yes. Despite outdated marketing aimed at male athletes, creatine is one of the safest and best-studied supplements available, and the evidence for benefit in women — for strength, lean mass, and possibly cognition — is strong. 3-5g daily of creatine monohydrate is the standard.
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About the Author
Candice Silver, MS, RDN, CDN is a Registered Dietitian Nutritionist based in New York City. She holds a Master of Science in nutrition and is credentialed by the Commission on Dietetic Registration (RDN) and certified by New York State (CDN). Candice works primarily with women navigating real-life nutrition questions — from gut health and hormones to family feeding and chronic conditions — with a practice rooted in evidence-based care and cultural respect.
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