A woman with long brown hair smiles with her eyes closed as sunlight and shadows from blinds fall across her face, radiating the natural glow of live probiotic skincare.

The Vitamin D You Can’t Get From a Pill

Most people know that sun exposure produces vitamin D. Fewer people know that vitamin D is only part of what it produces, and that the supplement industry has built an entire market around a story that the science no longer fully supports.

In Episode 05 of Esse’s Skin as it should be podcast series, which takes an unfiltered look at skin science and the assumptions that surround it, master chemist Trevor Steyn unpacks why the relationship between sunlight and skin is far more complex than public health messaging has ever acknowledged.

 

The supplement myth

A National Institutes of Health (NIH) study tracking 25,000* adults over five years found no measurable benefit from vitamin D supplementation compared to placebo. At the end of the study, the lead author concluded that vitamin D consumption produced no benefits whatsoever. Blood markers may rise, but health outcomes do not reliably follow.

The reason may lie in what supplementation actually replaces. When UVB light hits skin, it converts a precursor compound into three distinct molecules: vitamin D3, which accounts for roughly 26% of the output, and two additional sterols, Lumisterol and Tachysterol, which make up the remaining 74%. Research has shown both to be highly biologically active, and neither can be produced by a pill.

 

What the sun does for skin specifically

Low vitamin D has direct consequences for skin. It disrupts the process that regulates how skin cells differentiate and renew, resulting in thinner skin. It weakens barrier function by reducing tight junction formation. It drives chronic inflammation. Many people who believe they have inherently sensitive skin may simply be Vitamin D deficient.

The episode raises a point worth contemplating. Avoiding the sun specifically to prevent ageing, without accounting for what Vitamin D deficiency does to skin, may produce the opposite of the intended result.

 

The evolutionary mismatch

The body has its own system for managing sun exposure across seasons. As UV intensity increases in summer, skin deepens its pigmentation to protect against DNA damage. As light levels fall in winter, pigmentation naturally recedes, allowing greater UV penetration to sustain vitamin D synthesis. It is a seamless, self-regulating response built over two million years. Modern indoor life has largely disabled it. The average person now spends 93% of their time inside or in a car, with no equivalent mechanism to compensate.

Supplements were never the solution to that. Sensible, regular sun exposure is.

 

Hear the full conversation

Episode 05 of the Skin as it should be podcast goes deeper on the science, covering what a vitamin D winter is, how factors like latitude, skin tone, and time of day shape how much sun exposure is actually useful, and what a sensible, practical approach to sun exposure looks like day to day.

Listen to Skin as it should be, Episode 05, here.

 

Reference:

* Manson, J.E. et al. (2019). Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease. New England Journal of Medicine, 380, 33–44. https://www.nejm.org/doi/full/10.1056/nejmoa1809944