Could sunscreen cause vitamin D deficiency? Short answer: yes

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The short answer is yes. But before launching your SPF 30, dermatologists say that the relationship between sunscreen and vitamin D is much more nuanced than that.

According to Dr. Henry W. Lim, chairman emeritus of the dermatology department of the Henry Ford Health System and former president of the American Academy of Dermatology, if sun protection is provided in a thick layer, it "can effectively block the light of the sun and cause a lack of vitamin D synthesis in the skin, "said Lim. A thick layer roughly corresponds to about 1 ounce, or the size of a golf ball, for the whole body, he said.

"However, in the real world … most people are applying less than this amount," added Lim. In other words, the "SPF" used "is actually lower than the labeled SPF."

So you do not have to worry about vitamin D deficiency if you do not adequately protect the sunscreen. In an Australian study, adequate levels of vitamin D were maintained during the summer, whether individuals use a broad-spectrum sunscreen or a placebo cream. Researchers attributed the results in part to "lack of total skin coverage at all times".

Those who generously apply sunscreen and who wear SPF-protected hats and clothing when they are exposed to the sun – which LIM recommends to reduce the risk of skin cancer – will have a probability higher levels of vitamin D deficiency, explained Lim.

"For the vast majority of the public, the vitamin D content should not be a problem, but for those who practice strict protection, namely wearing sun protection clothing, hats, stay in the shade at night. outside and apply sunscreen – they need a higher risk, "said Lim.

Vitamin D deficiency versus risk of skin cancer

Vitamin D is synthesized in the skin when it is exposed to the sun's UVB wavelengths.

Thus, if 15 to 20% of the body surface is exposed to the sun without protection, for 15 to 20 minutes, two to three times a week, adequate vitamin D level can be achieved. But even with low levels of sunlight, cumulative sun damage can occur in the long term, Lim said.

Vitamin D: deficiency, food sources and what you need to know
"When the skin shines, there is damage to the DNA, and so with repeated exposure to low doses, damage to DNA could accumulate and potentially increase the risk of cancer." of skin and photoaging, "said Mr Lim. Squamous and basal cell carcinomas are the most common skin cancers in humans. They are correlated with the degree of sun exposure, while melanoma, the most deadly form of skin cancer, often results from intense and more intermittent sun exposure, Lim said.

"Patients need to use sunscreen to minimize their risk of skin cancer, which effectively prevents the body from making vitamin D. I tell patients that if we discover that smoking increases vitamin D levels, we do not would not tell them to smoke, "said Dr. Patricia Farris, dermatologist and member of the American Academy of Dermatology. "In other words, you can not recommend exposing patients to a known carcinogen (UV light) simply to increase their vitamin D levels."

How to have your D and eat it too

To reduce the risk of skin cancer and skin aging, dermatologists recommend sensitive photoprotection. It means wearing wide-brimmed hats, sunglasses and sun protection clothing. Photoprotective clothing, labeled "UPF", is tightly woven, which means that "the amount of UV light that can penetrate is quite low," Lim said.

A broad-spectrum sunscreen with an SPF of 30 or higher, which protects against harmful UVA and UVB rays, should be applied generously to all exposed areas of the body when outdoors for a prolonged period of time, so to minimize the risk of sunburn and skin cancer, explained Lim. (The sun protection factor, or sunscreen factor, is a relative measure that indicates the degree of protection against sunburn provided by sunscreen, for example, if you use SPF 30 sunscreen, it would take 30 times the UV dose to produce redness compared to the skin without sunscreen.)

Although people with darker skin are at a lower risk of sun-induced skin cancer, they should still follow these guidelines, according to Lim. The American Academy of Dermatology is developing photoprotective guidelines for individuals of different skin types, according to Lim.

Regarding the amount of vitamin D, Lim recommends taking a daily multivitamin, which usually contains a quantity of vitamin D that would get an adequate blood level of vitamin. Optimizing vitamin D levels is important for bone health and can help minimize bone thinning and the risk of fractures. The recommended dietary intake of vitamin D by the National Institute of Medicine, which is based on the person's minimal or no exposure to the sun, is:
  • 400 international units for infants / children from 0 to 1 years old
  • 600 IU for children, teenagers and adults from 1 to 70 years old
  • 800 IU for adults aged 71 and over

"To achieve adequate levels of vitamin D, it is best to take a multivitamin every day rather than rely on the sun.The first is simple and inexpensive, while preventing the development of skin cancer and aging of the skin. skin, "said Mr Lim.

Vitamin D supplements can also help and are very effective for those with low levels of vitamin D, Farris added.

In addition to vitamin D supplements, the American Academy of Dermatology recommends the use of a healthy diet including foods naturally rich in vitamin D, such as salmon, tuna, sardines, and Cod liver oil and egg yolk, as well as fortified foods and drinks. with vitamin D, such as cereals, yogurt, milk and orange juice.

Lisa Drayer is a nutritionist, author and contributor to CNN's health and nutrition.

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