Food and skin: vitamin C, collagen, acne and the sun

Ultraviolet radiation causes sunburn, early skin aging such as spots, wrinkles and leathery skin, and skin cancer, the most common cancer in the US. The FDA's advice is to limit time in the sun, especially from 10 a.m. to 2 p.m.; wear long sleeves, pants, a broad-brimmed hat and sunglasses; and use a broad-spectrum sunscreen with SPF 15 or higher regularly, even on cloudy days, reapplying at least every two hoursFDA. Only broad-spectrum sunscreens of SPF 15 or more help protect against the UV rays that raise the risk of skin cancer and early aging FDA.

No food or supplement comes close. Sunscreen does limit how much vitamin D your skin makes, but the NIH Office of Dietary Supplements notes that health experts still recommend SPF 15 or more when you are out for more than a few minutes; food and supplements can cover vitamin D NIH ODS.

The body needs vitamin C to make collagen, the main structural protein of skin NIH ODS. Severe deficiency, scurvy, shows up in the skin as small red or purple spots and corkscrew hairs, along with fatigue and inflamed gums NIH ODS. Adults need 75 mg a day (women) or 90 mg (men), plus 35 mg more for smokers NIH ODS. Citrus, peppers, kiwifruit, berries and broccoli supply that easily. Above that, there is no good evidence that extra vitamin C by mouth makes skin look younger.

Collagen supplements are a different question. A 2021 meta-analysis of 19 trials (1,125 participants, 95% women) reported better skin hydration, elasticity and wrinkles with hydrolyzed collagen compared with placeboDe 2021. A 2025 meta-analysis of 23 trials then split the results by funding and quality: trials not funded by companies, and high-quality trials, found no effect on hydration, elasticity or wrinkles. The authors concluded there is no clinical evidence to support collagen supplements for skin agingMyung 2025. Collagen is broken down into amino acids when you digest it, like any protein; bone broth is a food, not a skin treatment.

Dairy. A meta-analysis of 14 observational studies in 78,529 people aged 7 to 30 found milk, yogurt and cheese were each linked to higher odds of acne, including skim milk. The authors warned that the studies varied, adjusted results were weaker, and there was publication bias Juhl 2018. Observational links cannot show that milk causes acne.

High-glycemic foods. In a 12-week randomized trial in 43 young men with acne, a low-glycemic-load diet reduced lesion counts more than a control diet, but the diet group also lost weight, so the authors could not separate the two effects Smith 2007. The American Academy of Dermatology summarizes this evidence as small studies suggesting a low-glycemic diet may reduce acneAad.

If you suspect a food, try cutting it for 12 weeks (acne changes slowly) and judge by photos, not memory. Do not cut out whole food groups for a child or teenager without a plan for calcium and protein. Acne has effective treatments: the American Academy of Dermatology guideline gives strong recommendations for benzoyl peroxide, topical retinoids, topical antibiotics and oral doxycycline, and for isotretinoin in severe or scarring acne Reynolds 2024.