Dietary interventions in skin ageing: a systematic review and meta-analysis.

BACKGROUND: Nutrition is a modifiable factor in skin ageing, but its effects remain inconsistently quantified. This meta-analysis assessed human studies from the Web of Science on dietary intake and skin ageing, using pooled standardised mean differences (pSMD). Interventions included carotenoids, collagen, lipids and fatty acids, polyphenols, prebiotics and probiotics, and vitamins. We included full-text English articles and excluded non-human, disease-focused, topical or in vitro studies. Publication bias was assessed using Egger's test and funnel plots. Results are shown as forest plots. MAIN BODY: Sixty-one studies were meta-analysed. Collagen reduces wrinkles (pSMD = - 0.94 [- 1.39, - 0.49], p = 4.82 × 10 -5 ). Lipids and fatty acids (pSMD = - 0.62 [- 0.92, - 0.31], p = 7.89 × 10 -5 ) and polyphenols (pSMD = - 0.48 [- 0.74, - 0.21], p = 3.96 × 10 -4 ) also reduce wrinkles without significant publication bias. Several interventions improve skin hydration, including collagen (pSMD = 0.66 [0.29, 1.04], p = 5.99 × 10 -4 ), lipids and fatty acids (pSMD = 0.54 [0.28, 0.80], p = 4.36 × 10 -5 ), polyphenols (pSMD = 0.59 [0.37, 0.80], p = 6.43 × 10 -8 ), and prebiotics and probiotics (pSMD = 0.71 [0.25, 1.16], p = 2.64 × 10 -3 ). Specific interventions target distinct ageing phenotypes. Carotenoids most effectively reduce redness (pSMD = - 0.53 [- 1.02, - 0.04], p = 3.39 × 10 -2 ), and collagen reduces pigment spots (pSMD = - 0.16 [- 0.31, - 0.003], p = 4.56 × 10 -2 ). Lipids and fatty acids improve elasticity (pSMD = 0.49 [0.14, 0.83], p = 5.45 × 10 -3 ), while polyphenols strengthen barrier integrity (trans-epidermal water loss pSMD = - 0.50 [- 0.79, - 0.22], p = 6.39 × 10 -4 ). CONCLUSION: Dietary components target specific skin ageing phenotypes. Carotenoids, collagen, lipids and fatty acids, and polyphenols are particularly effective for redness, pigment spots, elasticity, and barrier integrity, respectively. Lipids, fatty acids, and polyphenols show broad benefits across multiple phenotypes. Shared mechanisms may contribute to overlapping effects. Evidence gaps remain, especially regarding carotenoids and vitamins. Future studies could explore combinatorial dietary interventions. This research is primarily supported by a Singapore National Medical Research Council grant.