Supplements — What the Evidence Actually Shows

Walk into any pharmacy or scroll through any wellness platform, and you will encounter hundreds of supplements claiming to support longevity, cognitive function, and metabolic health. The gap between the marketing and the evidence is, in most cases, substantial.

This is not to say that supplementation is without value. Some supplements have a genuine evidence base. The problem is distinguishing them from the much larger pool of products with plausible mechanisms but no meaningful human trial data.

The Hierarchy of Evidence

Before evaluating any supplement claim, it is worth understanding what kind of evidence underlies it. In ascending order of reliability:

1. In vitro studies (cells in a dish) — informative for mechanism, not clinical outcomes
2. Animal studies — useful, but human translation is far from guaranteed
3. Observational human studies — show associations, not causation
4. Randomised controlled trials — the gold standard, though quality varies enormously
5. Meta-analyses of high-quality RCTs — the most reliable basis for recommendations

Most supplement marketing draws on the first two categories. Robust human trial data is the exception, not the rule.

Where There Is Reasonable Evidence

Vitamin D — deficiency is widespread, particularly among people with limited sun exposure. Supplementation in those who are genuinely deficient has reasonable evidence for musculoskeletal and immune health. The evidence for broader longevity benefits is more contested, and supplementing without checking baseline levels is not well-supported.

Omega-3 fatty acids — a complex area. The REDUCE-IT trial demonstrated cardiovascular benefit with high-dose icosapentaenoic acid (EPA) in a specific high-risk population. The evidence for lower-dose fish oil in general populations is more modest.

Creatine monohydrate — among the most extensively studied supplements in existence. Evidence is strong for supporting muscle protein synthesis, and emerging data suggests potential cognitive benefits in older adults. It is one of the more robustly evidence-backed options available.

Magnesium — genuine deficiency is common in Western populations. Supplementation in those who are deficient supports sleep quality, muscle function, and metabolic health. As with vitamin D, benefit is concentrated in those who are actually deficient.

A Working Framework

Rather than asking “should I take this supplement?”, a more useful question is: “What is my current status, and what does the best available evidence suggest for someone in my situation?”

This is the domain of personalised, evidence-based medicine — assessing individual biomarkers, understanding evidence quality, and making decisions that are proportionate to what the evidence actually supports. It is rarely a simple yes or no.