Collagen supplements really did smooth wrinkles in pooled trials

Skin aging has become a recurring concern even among younger people, partly because rising life expectancy means skin has more decades to show its wear. That concern has fuelled a boom in nutricosmetics, supplements marketed for skin, with hydrolysed collagen the most prominent among them. Plenty of individual studies have claimed benefits, but individual studies are exactly where supplement marketing tends to find its favourite results. The question this review tackled is whether the randomised, placebo-controlled evidence, taken together, actually supports oral collagen for the visible signs of skin aging.

The authors searched Medline, Embase, Cochrane, LILACS and a database dedicated to negative results, deliberately hunting for unflattering findings as well as positive ones. Eligible studies were randomised, controlled trials in which neither participants nor researchers knew who received the real supplement, comparing oral hydrolysed collagen against placebo. Trials had to report at least one of four outcomes: skin wrinkles, hydration, elasticity or firmness. Nineteen studies were selected, covering 1,125 participants aged between 20 and 70, of whom 95% were women, and their results were pooled in a meta-analysis.

The grouped analysis favoured hydrolysed collagen over placebo for skin hydration, elasticity and wrinkles. The improvements in hydration and elasticity were confirmed again when the studies were broken into subgroups, which adds confidence that those two findings are not an artefact of how the trials were combined. Based on the pooled results, the authors conclude that taking hydrolysed collagen for 90 days is effective in reducing signs of skin aging, reducing wrinkles and improving elasticity and hydration.

Collagen has long sat in the awkward zone between marketing enthusiasm and scientific scepticism, and this review moves it a step towards respectability: the pooled, placebo-controlled evidence points the same way as the advertising, at least for hydration, elasticity and wrinkles. That said, the evidence base is heavily skewed, with 95% of participants being women, so whether men respond similarly is unknown. The review also cannot settle what happens beyond the trial periods studied, or disentangle which collagen products drove the benefit.

If you have wondered whether collagen supplements are pure marketing, this is evidence they are not: across 19 trials against placebo, skin hydration, elasticity and wrinkles all improved. The tested pattern in the authors' conclusion was daily use over 90 days, so this says nothing about shorter dabbling. The population studied was overwhelmingly women aged 20 to 70, which is worth knowing whichever side of that description you fall on. As always with pooled findings, the direction is more certain than the size of the change you would see in the mirror.