Skin is three jobs stacked on top of each other: a waterproof barrier on the surface, a collagen scaffold underneath, and defences against what sunlight does to both. Each one runs on specific nutrients, and most of them come from food.
The surface of skin is a wall of flattened cells held together by fats, mostly ceramides. That wall keeps water in and germs out. Under it, the dermis is a mesh of collagen and elastin fibres that gives skin its firmness and spring. Sunlight hits both. Some of it is good for you (vitamin D, nitric oxide), and some of it oxidises fats and breaks down collagen. Aged, wrinkled, slow-healing skin is what happens when the damage outruns the repair.
Flat cells in a fatty mortar keep water in. Vitamin A sets how fast new cells come up from below, and zinc runs the repair.
Collagen fibres give skin firmness. Vitamin C and glycine build them, and copper ties them together. Sugar glues them stiff (the red dots).
UV oxidises the fats in skin and switches on enzymes that break down collagen. What's in the skin decides how much damage a dose of sun does.
The same sun does more harm to skin that's low on repair nutrients and loaded with oxidisable fat.
Most visible skin ageing on the face and hands is sun damage: collagen broken down by UV-triggered enzymes, and DNA damage that becomes spots and, later, skin cancers. Burning is the clearest marker that the dose was too high. But sun also makes vitamin D and releases nitric oxide from the skin, and people who avoid it entirely do worse on heart outcomes. So the goal is regular, gradual exposure, not none.
Skin adapts. A few weeks of short, regular sessions in spring thickens the outer layer and builds a tan, which together raise the dose it takes to burn. The diet levers below raise it further.
Read more: Sunlight & Metabolic Health · Vitamin D
↑ back to the short listCells turn retinol into retinoic acid, which switches on the genes that set how fast skin cells divide, mature and shed. Low vitamin A gives dry, rough, bumpy skin. Tretinoin and isotretinoin, the strongest prescription treatments for wrinkles and acne, are retinoic acid itself, given at doses far above what food supplies. Food keeps the system stocked. The drugs push it hard.
Plants don't contain vitamin A. They contain beta-carotene, which some people convert well and many convert poorly. Retinol from animal foods skips that step.
Read more: Vitamin A · Wild Fish, Oysters & Venison
↑ back to the short listCollagen is about one-third glycine, with lots of proline. To fold it into a stable triple helix, the enzymes that finish it need vitamin C. Without vitamin C the collagen falls apart, which is scurvy. Copper then runs lysyl oxidase, the enzyme that cross-links finished fibres into a strong mesh. Muscle meat is rich in methionine and low in glycine, so a diet without skin, bones or broth runs short on the main raw material.
Collagen supplements look good in pooled trials: better hydration, elasticity and wrinkle depth after about 90 days. But a 2025 meta-analysis of 23 trials split them by funder. The benefit came from trials paid for by collagen makers, and the independent trials found no effect. The building-block argument still holds. The face-cream promises are weaker than the marketing.
Read more: Glycine / Collagen · Vitamin C · Copper · Bone Broth
↑ back to the short listLycopene, the red pigment in tomatoes, collects in skin and soaks up the reactive oxygen that UV creates. Two small randomised trials tested it as food. In one, 40 g of tomato paste a day with olive oil cut UV reddening after 10 weeks. In the other, 55 g a day for 12 weeks cut reddening and protected procollagen and mitochondrial DNA in skin biopsies. Cooking and fat both raise how much lycopene you absorb, so paste beats raw tomatoes.
It's a modest, slow effect, like a low-SPF layer built from the inside. It doesn't replace not burning.
Read more: Sauces · Fra Diavolo
↑ back to the short listEPA goes into skin cell membranes and dampens the inflammatory signalling UV sets off. In a Manchester trial, people who took 4 g of EPA a day for three months needed a bigger UV dose to burn, and showed less UV-induced p53, a marker of DNA damage. That's a high dose, more than fish alone supplies, but it shows the direction. Wild fish also brings vitamin D, selenium and astaxanthin, the red pigment in salmon.
Read more: Wild Fish, Oysters & Venison
↑ back to the short listLinoleic acid is the main polyunsaturated fat in skin, and it oxidises easily under UV. Skin does need a little of it for the ceramides in its barrier, but deficiency is very rare and takes almost none. What's in question is the excess. A Western diet built on soybean and canola oil loads skin with far more than the barrier uses.
In hairless mice, diets rich in polyunsaturated oil raised UV-induced skin cancer compared with saturated fat. The one human diet trial cut total fat, not linoleic acid in particular: 76 people with prior skin cancer went to 20% of calories from fat and grew fewer new pre-cancerous spots (actinic keratoses) over two years. That fits the idea but doesn't isolate it. No trial has cut linoleic acid alone and measured sunburn.
Read more: Linoleic Acid paper
↑ back to the short listGlucose sticks to proteins without an enzyme and forms advanced glycation end-products (AGEs). Collagen is long-lived, so it collects them. AGEs cross-link collagen fibres the wrong way, making them stiff and brittle, and the body's enzymes struggle to clear them. People with diabetes show this in their skin, and higher blood sugar tracks with looking older in cohort studies. It's the same insulin-resistance problem that drives heart disease, showing up in a different tissue.
Read more: Metabolic Health · Heart guide: insulin
↑ back to the short listAbout 5% of the body's zinc is in skin. Every step of repair uses it: cells dividing to fill a gap, enzymes clearing old scaffolding, and immune cells keeping the wound clean. Zinc deficiency shows up as slow healing, rashes and hair loss, and the genetic form causes raw, crusted skin that clears with zinc. Zinc has also been tested for acne, with modest benefit.
This is a quick guide. The evidence and references live on the linked pages. Not medical advice.