Skin
The Only Lever That Is Bigger Than All The Others
Ultraviolet exposure outweighs everything else on this website combined, including the product we sell.
Published 2026-08-29 · 8 minute read · Gelagen Notes
We sell a supplement, and this page argues that something free matters more than the thing we sell. Ultraviolet exposure does more to how skin looks over a lifetime than diet, supplements and topical routines combined, and it is not close.
Two Wavelengths, Two Jobs
UVB is the burning wavelength. It is strongest in summer, at midday, at altitude and near the equator, and it is blocked by window glass. It is also the wavelength that makes vitamin D in your skin, which is why that production stops for months at higher latitudes.
UVA is the ageing wavelength. It is far more constant across seasons and times of day, it passes through cloud, and it passes through window glass. It penetrates deeper into the dermis, where it degrades collagen and elastin.
That difference explains something people find counterintuitive: you can accumulate meaningful photoageing on grey days, through a car window, in February.
What Photoageing Actually Is
The visible signs people attribute to age — coarse wrinkles, uneven pigment, a leathery texture, broken capillaries — are largely cumulative UV damage rather than the passage of time itself. Intrinsic ageing, the kind that happens without sun, is much subtler: fine lines and gradual thinning.
The comparison that makes this vivid is the one dermatologists reach for constantly: the skin on the inside of your own upper arm, which has had very little lifetime sun, next to the back of your hand. Same person, same age, same diet, same supplements.
What To Do, In Order Of Effect
Daily broad-spectrum sunscreen. Every morning, all year, on face, neck and the backs of hands. Broad spectrum means it covers UVA as well as UVB, which the SPF number alone does not tell you.
Enough of it. Most people apply between a quarter and a half of the amount used to test the product, which means an SPF 50 applied thinly is not performing as an SPF 50. Roughly a third of a teaspoon for a face is the usual guide.
Reapply outdoors. Every two hours, and after swimming or heavy sweating. Indoors, away from windows, one application in the morning is realistic.
Shade and clothing. A hat and a long sleeve outperform any sunscreen because they do not wear off or get applied thinly.
No sunbeds. There is no version of a tanning bed that is a good idea.
Where The Supplement Sits In This
Well below all of the above, and it is worth being explicit about why. Nutrition influences the quality of what your skin builds next. Sunscreen prevents the damage that makes rebuilding necessary in the first place. One is a repair budget and the other is not spending.
Antioxidants including vitamin E and vitamin C do reduce part of the oxidative load UV generates, which is a genuine and modest contribution. It is not sun protection and nothing swallowed is.
Nothing here is an argument for avoiding daylight. Getting outside is good for sleep, mood and general health, and vitamin D synthesis is real. The target is never burning, not never going outdoors.
Quick Answers
Do I need sunscreen in winter?
Yes. UVA is comparatively constant year round and passes through cloud and glass, and it is the wavelength most associated with visible ageing.
Will sunscreen stop me making vitamin D?
In practice people apply too little, too unevenly, for it to eliminate synthesis. If you are concerned about vitamin D, test it and supplement rather than burning for it.
Is a foundation with SPF enough?
No. The tested SPF is achieved at a thickness nobody applies with makeup. Treat it as a bonus on top of sunscreen, never as a replacement.