The Short List of Supplements That Actually Work

Why the list is so short

Walk into any pharmacy and the shelves promise a longer, sharper, more energetic life in capsule form. The reality, when you read the trials rather than the labels, is humbling. The large majority of supplements have either never been tested against a placebo in humans for a hard outcome, or have been tested and failed. That does not always mean they are harmful — but it does mean you are usually paying for hope, not evidence.

The reason is partly biology and partly regulation. Biologically, a nutrient only helps if you are short of it; topping up a level that is already adequate rarely does anything, and occasionally does harm. Regulation-wise, supplements in most countries are sold without the efficacy testing demanded of medicines, so a product can reach the shelf on the strength of a plausible mechanism and a marketing budget alone. The result is an industry where the burden of proof sits on you, the buyer, not on the seller.

Clean Longevity's approach is to start from the question "what would I keep if I could only keep the things that survive a randomised controlled trial?" The list below is what is left. It is deliberately short, and that shortness is the point.

Fibre: the supplement that is really a food

If one thing deserves the top of the list, it is dietary fibre — and it makes a useful starting point precisely because it blurs the line between supplement and food. A landmark series of systematic reviews and meta-analyses published in The Lancet in 2019 by Reynolds and colleagues pooled almost 135 million person-years of observational data alongside dozens of randomised trials.^[1] People with the highest fibre intakes had roughly 15–30% lower rates of all-cause and cardiovascular mortality, coronary heart disease, stroke, type 2 diabetes and colorectal cancer than those with the lowest intakes, and the clinical trials showed lower body weight, blood pressure and cholesterol with higher fibre intake.

The dose that captured most of the benefit was around 25–29 grams a day, with the curve suggesting still more might help. Most people in Western countries eat well under that. The cleanest way to get there is food: legumes, whole grains, vegetables, fruit and nuts. A fibre supplement such as psyllium is a reasonable bridge if your diet falls short, but it is a backstop, not a substitute for the pattern of eating that delivers fibre along with everything else that travels with it.

Omega-3: real, but narrower than the hype

Marine omega-3 fatty acids (EPA and DHA) are among the most studied supplements on the market, and the evidence is genuinely mixed in an instructive way. The large VITAL trial, reported by Manson and colleagues in the New England Journal of Medicine in 2019, randomised nearly 26,000 generally healthy adults to 1 gram a day of fish oil or placebo.^[2] For the headline endpoint — a composite of heart attack, stroke and cardiovascular death — omega-3 did not beat placebo.

But buried in the secondary results was a meaningful signal: total heart attacks fell by about 28% in the omega-3 group. That is the nuance the supplement industry oversells and the sceptics underplay. Omega-3 is not the universal life-extender the marketing implies, but for specific cardiovascular endpoints, particularly in people who eat little oily fish, there is a defensible case. The cleanest route, again, is food — two servings of oily fish a week — with a supplement as a reasonable option for those who will not or cannot eat fish.

Vitamin D: only if you are actually low

Vitamin D is the perfect illustration of the "correct a deficiency" principle. In the same VITAL programme, the vitamin D arm — 2,000 IU a day in a largely vitamin-D-replete population — produced no reduction in cancer or major cardiovascular events compared with placebo.^[3] Supplementing people who already have adequate levels did essentially nothing for those hard outcomes.

That is not an argument that vitamin D is useless. It is an argument that it is useful precisely when you are deficient — which is common in higher latitudes, in winter, in people with darker skin and in those who spend little time outdoors. The clean approach is to test rather than guess: if a blood test shows you are low, correcting it is sensible and cheap. If you are replete, another capsule is unlikely to add anything. Blanket high-dose supplementation "just in case" is exactly the kind of hopeful clutter this site exists to cut.

Creatine: not just for the gym

Creatine monohydrate is one of the few supplements that has earned its reputation through decades of consistent trials. Its best-established benefit is in muscle: combined with resistance training, it reliably increases strength and lean mass, which matters far beyond athletic performance. A 2021 meta-analysis by Forbes and colleagues found that creatine taken alongside resistance training significantly augmented gains in lean tissue mass and strength in older adults compared with placebo.^[6] A separate 2023 meta-analysis using direct imaging confirmed a measurable, if modest, increase in muscle thickness when creatine was added to training.^[7] Muscle and strength are themselves predictors of healthy ageing, and the years after 40 are when preserving them becomes a longevity issue, not a vanity one.

Creatine is also cheap, well tolerated, and among the most studied compounds in sports science, with a strong safety record at standard doses of around 3–5 grams a day. Emerging work on cognition and fatigue is interesting but less settled, so we would not promise it. What we will say is that for an adult doing strength training and wanting to protect muscle into later life, creatine is one of the rare supplements where the evidence comfortably justifies the spend.

The honest "don't bother" pile

A clean list is defined as much by what it excludes as what it includes. Several of the most popular categories simply do not hold up, and a few are worse than neutral.

The starkest example is high-dose vitamin E. The SELECT trial, reported by Klein and colleagues in JAMA in 2011, randomised over 35,000 healthy men and found that those taking 400 IU of vitamin E a day had a statistically significant increase in prostate cancer risk — a hazard ratio of 1.17.^[4] This is the cautionary tale at the heart of the antioxidant story: more is not better, and a plausible mechanism (mopping up free radicals) can produce the opposite of the hoped-for result in a real human population.

Standalone high-dose antioxidant pills — beta-carotene, vitamin C megadoses, and similar — have a similarly disappointing or worrying record in large trials, and routine multivitamins have repeatedly failed to extend life or prevent disease in healthy, well-nourished people. The evidence here is more nuanced than "always pointless": a recent large trial, COSMOS-Mind, reported by Baker and colleagues in 2022, found a modest benefit of a daily multivitamin on cognition in older adults, while a cocoa-flavanol extract showed none.^[5] That is a genuine signal worth watching — but a single modest cognitive finding is a long way from the broad disease-prevention claims that sell multivitamins, and it does not change the basic verdict for a healthy younger adult eating a varied diet.

How to read a supplement honestly

Beyond the specific list, a few habits protect you from almost all of the clutter:

• Ask for a human outcome. "Improves a marker in a test tube" or "worked in mice" is not the same as helping a person live better or longer. Look for randomised trials in humans.
• Assume "more" is not better. The vitamin E story shows that megadoses can flip from neutral to harmful. Nutrients tend to have a window, not a straight line.
• Correct, don't carpet-bomb. Test for deficiencies and fix those specifically, rather than taking everything on the off-chance.
• Mistrust proprietary blends. If a label hides doses behind a "blend," you cannot know whether any ingredient is present in an effective amount. Clean products tell you exactly what you are taking.
• Spend on food and the free levers first. Fibre, sleep, movement and sunlight outperform almost any bottle, and they are cheaper.

The clean takeaway

The supplement industry thrives on the gap between what sounds plausible and what has been proven. Close that gap and the shopping list shrinks dramatically: enough fibre, oily fish or omega-3, vitamin D if you are genuinely low, and creatine if you train. Almost everything else is optional at best and, in a few cases, worth actively avoiding.

That is not a deprivation message — it is a liberation. A short, evidence-based list is easier to stick to, cheaper to maintain, and far more honest than a bathroom cabinet full of capsules bought on hope. Less, but better, is the whole point.