As a Biochemist I sometimes hear or see that some people are wary of wearing higher spf products because it will affect their vitamin D levels.

Vitamin D is actually more a steroid hormone than a vitamin and the inactive precursor is produced in the skin when exposed to UVB (Holick et al, 1980). However, a lot of food is fortified with the inactive form as well. Most breakfast cereals and milk are fortified because the exposure to UVB is so varied depending on where you live. Someone further from the equator will have a much lower exposure to UVB in the winter than someone living at the equator.

Also the actual use of spf varies, it is not always reapplied every 2 hours exactly nor is the full recommended amount applied in the general population. An spf of 50 is lower in practice during field testing. So some UVB will reach the skin and catalyse the production of the inactive precursor (Neale et al, 2019).

To produce the active form the precursor is broken using two enzymes, one in the liver followed by one in the kidneys. In the blood the hydrolysed form produced in the liver is measured to give an indication of vitamin D levels. You may be told by your GP that you are vitamin D insufficient (a little lower than average for your age group) or deficient (significantly lower). This can be easily offset using diet rather than increasing your risk of skin cancer due to UVB exposure. Vitamin D supplements are actually recommended particularly in winter and are also important for POC because melanin competes for the UVB.

So, with that in mind vitamin D supplements are actually recommended for almost everyone. Current research suggests that in practical field trials spf use does not interfere with vitamin D levels in the serum of healthy individuals (Passeron et al 2019). However, this is affected by the variability of spf application (Neale et al, 2019).

Holick MF, MacLaughlin JA, Clark MB, Holick SA, Potts JT, Anderson RR, et al. (October 1980). "Photosynthesis of previtamin D3 in human skin and the physiologic consequences". Science. 210 (4466): 203–5.
Neale RE, Khan SR, Lucas RM, Waterhouse M, Whiteman DC, Olsen CM. The effect of sunscreen on vitamin D: a review. Br J Dermatol. 2019 Nov;181(5):907-915. doi: 10.1111/bjd.17980. Epub 2019 Jul 9. PMID: 30945275.
Passeron T, Bouillon R, Callender V, Cestari T, Diepgen TL, Green AC, van der Pols JC, Bernard BA, Ly F, Bernerd F, Marrot L, Nielsen M, Verschoore M, Jablonski NG, Young AR. Sunscreen photoprotection and vitamin D status. Br J Dermatol. 2019 Nov;181(5):916-931.

Vitamin D and Sunscreen

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