Rumour: “Sunscreen causes vitamin D deficiency” — What does the science say?

Short answer: on the available evidence, no. In theory sunscreens can reduce vitamin D production in the skin, and under laboratory conditions they have been shown to do so. However, in field studies in which people used sunscreen in everyday life and on holiday, no significant fall in vitamin D levels was found. A systematic review published in 2019 and an international expert consensus reached the same conclusion. An important reservation is that there are few field studies with very high sun protection factor products. If you are at risk of vitamin D deficiency, the solution is not to give up sunscreen but to assess the situation with your physician.

Where does the rumour come from?

Behind the rumour lies a correct piece of biology. A precursor substance in the skin is converted to vitamin D by the sun's UVB rays. The rays that cause sunburn are also predominantly UVB. In other words, the wavelengths that redden the skin and the wavelengths that start vitamin D production largely overlap. That a product which prevents sunburn should also block vitamin D production is therefore an expected result.

This expectation has also been supported by experiments. According to the systematic review of the subject, in four experimental studies using an artificial ultraviolet source, sunscreen markedly reduced light-induced vitamin D production. The rumour arises from carrying this laboratory finding directly over into everyday life.

What have real-life studies shown?

The same systematic review searched the studies published up to the end of 2017; alongside the four experimental studies it examined three field studies (two of them randomised controlled trials) and 69 observational studies. In the randomised controlled field studies, daily sunscreen use was found to have no effect on vitamin D levels. In most of the observational studies either no association was seen or vitamin D levels were found to be higher in those who said they used sunscreen. Although this last finding seems surprising, its explanation is simple: people who use sunscreen are often people who spend more time outdoors.

One of these field studies was carried out in Australia. For one summer, 113 people aged forty and over used either a broad-spectrum sunscreen or a cream containing no active ingredient every day; neither the participants nor the researchers knew who was using which. At the end of the summer, vitamin D levels had risen to a similar extent in both groups, and no one's value, including those over seventy, had fallen outside the normal range.

In a more recent study, volunteers spent a week on holiday in a region where the ultraviolet index was very high; some were given sunscreen and taught how to apply it at a sufficient thickness. Those who used the sunscreen as recommended did not get sunburnt, and yet their blood vitamin D levels rose significantly. In the group that used sunscreen according to their own habits the increase was greater, but sunburn was also seen in this group.

An international panel made up of thirteen experts from the fields of endocrinology, dermatology, photobiology and epidemiology also reviewed the publications and reached this consensus: sunscreens applied for daily use and outdoor activities do not compromise vitamin D status in healthy people.

It is also necessary to know the limits of the evidence. The products used in the field studies had a moderate sun protection factor; there are few similar studies with the very high sun protection factor products widely recommended today, and the authors of the review state this plainly. In addition, some of the authors of the expert consensus and of the holiday study work in the cosmetics industry. The conclusion should therefore be read not as 'it definitely has no effect' but as 'no significant fall has been shown in real life'.

Why does it not lower vitamin D in practice when in theory it should?

• The product is applied thinly: the sun protection factor is measured in the laboratory with a specified, thick layer. In everyday life people mostly use less product than this; the real protection falls below the value on the label.
• Some areas are left uncovered: areas such as the ears, nape, backs of the hands and hairline are often skipped; the arms and legs are not areas where product is applied every day.
• Reapplication lapses: the product is reduced by sweat, water and friction; when it is not reapplied during the day, protection falls.
• No sunscreen blocks all the rays: even a correctly used product lets through a small part of UVB. The holiday study showed that vitamin D production continued even with sunscreen applied thickly enough to prevent sunburn.
• Use goes up with time spent outdoors: sunscreen is mostly applied on days when a long time will be spent in the sun; total exposure is still high.

These points do not mean that there is any benefit in using sunscreen carelessly. Applying it thinly and not reapplying also reduce protection against the risk of sunburn, pigmentation and skin cancer. The right amount, the interval for reapplying and the choice of product are explained in our article “Sunscreen Guide”.

Do you need to sunbathe for vitamin D?

The American Academy of Dermatology does not recommend getting vitamin D by going out in the sun or from sunbeds. Its reasoning is this: ultraviolet rays increase the risk of skin cancer, and no safe level of exposure has been defined that provides sufficient vitamin D production without raising the risk of skin cancer. The Academy recommends that healthy adults get their vitamin D from foods that naturally contain vitamin D and foods fortified with vitamin D.

This does not mean that the sun has to be avoided altogether. In everyday life the skin receives some ultraviolet light even when sunscreen is used. What is meant is that deliberately sunbathing without protection, or giving up sunscreen, in order to obtain vitamin D is not recommended. For the part played by the sun's rays in skin ageing and pigmentation, see our article “Rumour: You don’t need sunscreen in winter or on cloudy days — What does the science say?”.

Season and geography matter too. The United Kingdom's National Health Service states, for its own country, that in the autumn and winter months sunlight is not strong enough for vitamin D production and that during this period vitamin D needs to be obtained from food or a supplement. In other words, the main reason for low vitamin D in winter is not sunscreen but the sun itself. This information applies to the latitude of the United Kingdom; in regions further south the picture may be different.

Who is at higher risk of vitamin D deficiency?

There are factors that affect vitamin D levels far more strongly than sunscreen. The groups highlighted by health organisations are these:

• People who rarely go outdoors: those who are housebound or live in a care home
• People who cover most of their skin with clothing when outdoors
• People with dark skin: the pigment in the skin filters part of the light needed for vitamin D production
• Babies and young children: for this age group the decision on a supplement belongs to the paediatrician
• People with a light-sensitivity disorder: because these people use high sun protection factor products, protective clothing and shade together, the expert consensus recommends monitoring vitamin D levels in this group and a supplement if needed

The expert consensus recommends that vitamin D levels be checked not in everyone but in those at risk of deficiency. If you are in one of these groups, or have had complaints such as tiredness and bone and muscle pain for a long time, tell your physician; your physician decides whether tests are needed.

What is the solution if you are at risk of deficiency?

The solution is not to leave the skin unprotected. Vitamin D is found in oily fish, egg yolk and foods fortified with vitamin D; however, it is not always easy to reach an adequate level through diet alone. In that case your physician may recommend a supplement.

• Your physician decides on a supplement, its dose and its duration. Vitamin D is a fat-soluble vitamin, and taking more than needed over a long period can be harmful.
• Do not start high-dose products on an acquaintance's advice without your blood level having been checked.
• If you are pregnant or breastfeeding, have kidney disease or take regular medication, be sure to discuss a supplement with your physician.
• Sunbeds are not recommended as a source of vitamin D.

Why does this matter particularly after a medical aesthetic procedure?

The situation in which this rumour does the most harm is precisely the period when sun protection is most necessary. After laser, chemical peels, microneedling and similar procedures, the skin is more sensitive to ultraviolet rays. During this period unprotected sun exposure increases the risk of darkening of the skin after the procedure, especially in dark skin and in people prone to pigmentation. The details are in our articles “Burns and Pigmentation Changes after Laser and IPL” and “Laser, IPL and Chemical Peels on Olive and Darker Skin”.

In melasma, sun protection is the foundation of treatment; giving up sunscreen can lead to the patches darkening and the treatment being wasted. This subject is dealt with in our article “Dark Spots and Melasma”. Those considering laser for pigmentation can look at the sections on sun protection in our article “Pigment Lasers”, and those using retinoid-containing products at those in our article “Retinoid Guide”. The general principles after a procedure are in our article “Aftercare Following Medical Aesthetic Procedures”.

In the period after a procedure, rather than giving up sunscreen out of concern about vitamin D, raise your concern with your physician. If necessary, your vitamin D level will be assessed separately; the two matters are not alternatives to each other.

Conclusion

That sunscreen can reduce vitamin D production is correct in theory and has been shown in the laboratory. However, studies examining how people actually use the product have not shown that daily use significantly lowers vitamin D levels. For very high sun protection factor products the data are limited; this uncertainty is a reason not to give up sun protection but, if you are in a risk group, to discuss your vitamin D level with your physician. Sunbathing for vitamin D is not recommended; if there is a deficiency, the solution is diet and a supplement where the physician considers it appropriate.