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Vitamin D Debate Ignites Sunscreen Controversy: Experts Clash Over Facts

A study suggesting that vitamin D — which humans produce during sun exposure — may help the immune system fight cancer has triggered a debate among experts about whether wearing sunscreen is harmful.

Reports suggest that up to 42% of adults in the United States have a vitamin D deficiency. Low vitamin D levels are linked to an increased risk of several health conditions, including heart disease. Research has also found that taking vitamin D supplements may reduce the risks of developing dementia and diabetes.

Recently, a mouse study published in Science found that vitamin D levels may impact the gut microbiome and improve cancer immunotherapy and immunity against tumors.

The study also found that in humans, low vitamin D levels were linked with tumor development, and vitamin D activity gene signatures were associated with improved responses to immunotherapy.

In a May 13 X post, Tim Spector, M.D., a microbiome, nutrition, and genomics researcher, made controversial remarks about the study, setting off intense debate about sunscreen use. Spector hinted that people who use sunscreen or sunblock may not be getting enough vitamin D through sun exposure.

The post caught the attention of one of the study's authors, Caetano Reis e Sousa, an assistant research director at The Francis Crick Institute and head of the Immunobiology Laboratory. Reis e Sousa accused Spector of grossly misinterpreting the findings.

Reis e Sousa's post led to several heated replies, including one person questioning whether sunscreen blocks vitamin D absorption and another claiming to have never worn sunscreen, calling it "a pointless and unnecessary risk."

Meanwhile, some people commenting on Spector's post demanded that it be deleted.

"You have badly misunderstood the scientific data and, to be frank, show a poor understanding of the role of vitamin D in both oncogenesis and immunology. This is dangerous advice and needs to be deleted," one X user wrote.

Are people turning away from sunscreen?

Amid the sunscreen debate on social media, a new survey from the American Academy of Dermatology (AAD) revealed that Gen Z adults, specifically 18 to 25-year-olds, are putting themselves at risk of developing skin cancer due to rising rates of tanning and burning among people in this age group.

Moreover, the investigators found that over half of Gen Z adults were unaware of one or more sunburn-related risks, including skin cancer.

The survey results also showed that 27% of Americans only use sunscreen when prompted by another person. Among Gen Z individuals, that percentage jumped to 37%.

Sunscreen safety issues

A 2023 review of research published in Applied Sciences suggests that some chemicals in sunscreens or sunblock may disrupt endocrine function. The researchers also say specific sunscreen chemicals are potentially carcinogenic, neurotoxic, or pose risks to human reproduction.

However, a risk assessment of zinc oxide, an ingredient in some sunscreens, found the compound is virtually non-toxic in animal models and safe to use in cosmetic products. In addition, research investigating the safety of titanium dioxide in sunscreen products found that the compound was not carcinogenic or toxic to reproductive health when applied to the skin.

In 2021, the U.S. Food and Drug Administration (FDA) proposed updated regulations for sunscreens. The proposed order suggests sunscreens containing zinc oxide and titanium dioxide are "generally recognized as safe and effective" (GRASE).

However, due to safety issues, the agency does not consider sunscreens containing aminobenzoic acid (PABA) and trolamine salicylate as GRASE.

In addition, the FDA did not give GRASE status to several other sunscreen chemicals due to a lack of data showing their safety and effectiveness.

These include:

  • Cinoxate
  • Dioxybenzone
  • Ensulizole
  • Homosalate
  • Meradimate
  • Octinoxate
  • Octisalate
  • Octocrylene
  • Padimate O
  • Sulisobenzone
  • Oxybenzone
  • Avobenzone

Should people use sunscreen?

According to the AAD, skin cancer is the most common type of cancer in the U.S. It's estimated that one in five Americans will be diagnosed with some form of skin cancer in their lifetimes.

The AAD says people can reduce their risk of skin cancer by staying in the shade, wearing sun-protective clothing, and using broad-spectrum (UVA and UVB) sunscreen with an SPF of 30 or higher.

person using sunscreen
Image by Studio KIWI via Shutterstock

In a follow-up post, Spector told X users that he based his opinions about not using sunscreen year-round on discussions with his wife, a consultant dermatologist. Spector said several clinical studies show vitamin D and sunshine are helpful for melanoma survival.

"I don't believe ALL cosmetics need SPF 30+," Spector concluded.

It is unclear whether sun exposure can help increase the survival rate of melanoma. However, a study published in 2023 suggests that people should not avoid the sun due to the unwanted health risks associated with vitamin D deficiency.

Still, scientists say that people should use sun protection strategies like sunscreen as sunscreens don't significantly interfere with the body's vitamin D production.

In contrast, AAD experts do not recommend getting vitamin D from sun exposure or indoor tanning. Instead, they say people should obtain vitamin D from fortified or vitamin D-rich foods.

While the experts continue debating, there are points people can consider when deciding whether to avoid the sun or use sunscreen.

For example, in addition to dietary intake, vitamin D supplements can help boost levels in the body. Individuals concerned about their vitamin D status can visit their healthcare provider to determine if their levels are low and whether supplements are needed.

Moreover, people worried about sunscreen safety could consider using sunscreen products with an FDA GRASE status, such as zinc oxide or titanium dioxide. Still, a healthcare provider can help determine the best type of sun protection based on an individual's health status and skin care needs.

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