What the large randomised trials found when they tested the four supplements everybody takes, which one came through, and how to read a label without being sold to.
Kratos Natural · Domain: Supplements
1. When is a supplement worth taking?
A supplement can do one of two things: correct a deficiency, or act like a drug. The first is usually worth doing when a test says you are short. The second needs the same evidence a drug needs, and almost nothing on a shop shelf has it.
Everything below is sorted by that rule, and the answer for most of the shelf is "correct a shortage you have actually measured, and stop there."
2. Does vitamin D work?
The VITAL trial randomised 25,871 people to 2,000 IU of vitamin D₃ a day or placebo, for a median of 5.3 years. It did not reduce the incidence of invasive cancer or of major cardiovascular events[1].
That is the largest test anybody has run of the thing vitamin D is sold for, and it came back negative.
What it does not say is that vitamin D is useless. VITAL enrolled a largely replete population: correcting an actual deficiency is a different question from supplementing people who are not short, and the trial answered the second. Deficiency is common in the Netherlands in winter, particularly in people with darker skin, who cover up, or who are indoors all day, and it is cheap to measure.
So: test, then treat. The hub tracks 25-hydroxyvitamin D with its reference range for exactly this. Taking 2,000 IU a day on the assumption you are short is the thing VITAL tested, and it did not pay.
3. Does omega 3 work?
The other half of VITAL randomised the same people to 1 gram a day of marine omega-3. It did not reduce major cardiovascular events or cancer incidence[2].
A meta-analysis of 13 randomised trials covering 127,477 participants found a more nuanced picture: marine omega-3 supplementation was associated with lower risk of myocardial infarction, coronary heart disease death and total coronary heart disease, with the risk reduction appearing to grow at higher doses, and no significant effect on stroke[3].
So: a real but modest effect on the heart, in the specific direction of coronary events, at doses above the one gram that most capsules contain. That is a long way from the label on the box, and it is roughly what the fish on your plate would suggest.
4. Does creatine work?
The exception on this page: cheap, extensively studied, and it does what it says. The International Society of Sports Nutrition's position stand concludes that creatine monohydrate is the most effective ergogenic nutritional supplement available for increasing high-intensity exercise capacity and lean mass during training, with no evidence of harm in healthy people at recommended doses over short or long-term use[4].
Dose: 3 to 5 grams a day of creatine monohydrate. No loading needed unless you are in a hurry. No cycling. Monohydrate, because everything else is the same molecule with a higher price.
5. Do you need protein powder?
Not a supplement so much as food in a tub, and the honest question is whether you need the tub.
The meta-analysis and meta-regression: protein supplementation increased gains in muscle mass and strength during resistance training, with the benefit plateauing at around 1.6 g per kilogram of body weight per day[5]. A separate meta-analysis of protein intake in healthy adults lands in the same range[6].
Which means the powder is a convenience for reaching a number, not a compound with its own effect. If you hit 1.6 g/kg from food, a shake adds nothing the trials can see.
6. How do you read a label?
Four things, and they take thirty seconds:
- The form and the dose per capsule, not per "serving" of four capsules.
- The compound, not the marketing name. Magnesium bisglycinate and magnesium oxide are different products; the second is mostly a laxative.
- A certificate of analysis, from a lab that is not the manufacturer. Supplements are food law, not medicines law: nobody checks the contents before it reaches a shelf.
- What it is dosed against. A product should be able to name the trial its dose came from. If it cannot, the dose is a decision made by marketing.
7. What we honestly do not know
Whether correcting a real vitamin D deficiency produces the outcomes VITAL looked for. VITAL did not test that population[1].
Why the omega-3 trial and the meta-analysis disagree. Dose is the leading explanation, and it is not settled[2][3].
Whether creatine's benefits outside sport are real. Cognition and mood are studied, promising and not settled; the position stand's confident half is about exercise[4].
Almost everything about most of the shelf. Absence of a trial is not evidence of absence, and it is also not a reason to spend money.
8. When should you ask a doctor first?
- You take blood thinners (omega-3 and vitamin E both matter here)
- You take medication for blood pressure, diabetes, thyroid or epilepsy
- You have kidney disease (creatine and protein both need checking)
- You are pregnant or breastfeeding
- You are about to have surgery
And a general one: do not take a fat-soluble vitamin at high dose without a blood test. D, A, E and K accumulate; the water-soluble ones mostly do not.
9. Sources
- Manson JE, Cook NR, Lee IM, et al. Vitamin D supplements and prevention of cancer and cardiovascular disease. New England Journal of Medicine, 2019. PMID 30415629
- Manson JE, Cook NR, Lee IM, et al. Marine n-3 fatty acids and prevention of cardiovascular disease and cancer. New England Journal of Medicine, 2019. PMID 30415637
- Hu Y, Hu FB, Manson JE. Marine omega-3 supplementation and cardiovascular disease: an updated meta-analysis of 13 randomized controlled trials involving 127,477 participants. Journal of the American Heart Association, 2019. PMID 31567003
- Kreider RB, Kalman DS, Antonio J, et al. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. JISSN, 2017. PMID 28615996
- Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength. British Journal of Sports Medicine, 2018. PMID 28698222
- Nunes EA, Colenso-Semple L, McKellar SR, et al. Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults. Journal of Cachexia, Sarcopenia and Muscle, 2022. PMID 35187864
More free knowledge at kratosnatural.com.
© Kratos Natural. This guide is free: read it, keep it, print it, pass it to anyone you like. What you may not do is sell it or present it as your own work. The knowledge belongs to everyone. The text stays ours.