Vitamin C

No trial has ever compared retinol with vitamin C for aging skin. Here is what each is actually shown to do, and where the evidence runs out.

Does vitamin C tighten saggy skin? No. The one trial to measure elasticity found a small dip, not a gain. Sagging is an elastin problem, not a diet one.

Vitamin C builds the collagen in artery walls, but trials found no drop in cardiovascular events. What it does, what it can't, and where evidence stops.

What organ does vitamin C affect? All of them - but it pools in the adrenal glands, brain and eyes, and leaves through the kidneys, where the one caution sits.

Which disease is caused by low vitamin C? Scurvy — and about 10 mg a day prevents it. Where being low ends and the disease begins, and why cases are rising. 

Does vitamin C help arthritis? Getting enough matters, but extra has shown little benefit. See the evidence for osteoarthritis, rheumatoid arthritis and gout.

Can too much vitamin C cause joint pain? Rarely. See the two medical exceptions, why too little vitamin C is the better-documented problem, and what to check.

Is vitamin C good for hair growth? It helps if you're low. See what deficiency does to hair, why iron matters more, and what the research hasn't shown. 

What does vitamin C do for you? It builds collagen, stocks immune cells, unlocks plant iron and aids 18 enzymes. What the evidence shows, and what it doesn't. 

Sustained 1,000mg vitamin C doses blunted mitochondrial gains in trials. What athletes should know about oxidative stress, recovery and race-week timing.

Surgery drops plasma vitamin C by 39% in the first week, and 21% of patients start deficient. What the evidence says about vitamin C wound healing.

Your body cannot finish a collagen fibre without vitamin C. What the evidence supports for skin, joints and tissue repair — and where it stops.