Vitamin D is produced in the skin when exposed to sunlight. Therefore, when using sunscreen on the skin, is Vitamin D production inhibited?
This has been a controversial question for many years. The current evidence suggests that sunscreen does block a part of Vitamin D production, but with negligible amounts.
Studies have found that by blocking ultraviolet rays, sunscreen limits the vitamin D we produce. But the question is to what extent.
A few studies have concluded that the effect is significant — a reduction as great as tenfold. But more recent, randomized studies that followed people for months and in some cases years suggest that the effect is negligible. While sunscreen does hamper vitamin D production, these studies say, it is not enough to cause a deficiency.
Dr. Lim added that rather than cutting back on sunscreen, people concerned about vitamin D should consume more foods rich in vitamin D, like salmon, milk and orange juice.
Source: New York Times Article, Emphasis Mine
Studies cited in the article
Matusoka LY et al. Chronic sunscreen use decreases circulating concentrations of 25-hydroxyvitamin D. A preliminary study. PubMed link
Marks R et al. The effect of regular sunscreen use on vitamin D levels in an Australian population. Results of a randomized controlled trial. PubMed link
Farrerons J et al. Clinically prescribed sunscreen (sun protection factor 15) does not decrease serum vitamin D concentration sufficiently either to induce changes in parathyroid function or in metabolic markers. PubMed link
Vitamin D is produced in the skin. There are two subtypes of UV radiation: UVA and UVB. UVA is primarily responsible for photoaging, and UVB for the superficial burning that results from sun exposure (2).
UVB electromagnetic radiation converts 7-dehydrocholestrol to pre-vitamin D3, which is then converted into Vitamin D3 (1). Sunscreens with an SPF rating absorb or reflect (depending on the filters used) UVB light (2). Without UVB light, 7-dehydrocholestrol cannot be converted into pre-vitamin D. It may also be of interest to note that glass blocks UVB (but not UVA radiation) and thus has a similar effect on Vitamin D production (1).
In reality, however, people rarely apply sunscreen well enough so that Vitamin D production completely ceases (3).
In short, yes sunscreen does inhibit the production of Vitamin D, although in most cases not to such an extent that Vitamin D deficiency becomes a concern.