In an era of growing skin cancer concerns, Vitamin D is drawing some attention for its emerging role in preventing certain cancers. Studies show that vitamin D may trigger the natural death of malignant cells, inhibit the growth of blood vessels feeding tumours, and promote the differentiation of skin cells. 

But unprotected exposure to sunlight may not be the best possible defense against skin malignancies as  benefits of its enabling your body to produce Vitamin D are far outweighed by the risk posed by the UVA exposure. Here’s why: 

Does Vitamin D protect from skin cancer?

Vitamin D is synthesized in the skin when it’s exposed to the sun’s ultraviolet B (UVB) rays. While adequate vitamin D levels have been linked to a reduced risk of several cancers, including colorectal and breast cancers, its connection to skin cancer is more complex. 

"Even if vitamin D had an anti-skin cancer effect, it is not sufficiently strong to prevent skin cancer from occurring," Dr Shazia Zaidi, a dermatologist at Metro Multi Specialty Hospital in Noida, told First Check. She emphasized that the damaging effects of UVA rays—which are not counteracted by vitamin D—are the main culprits behind skin cancers like basal cell carcinoma and melanoma.

Dr Zaidi clarified, “When you’re exposed to sunlight, you’re getting both UVA and UVB rays. The UVB component converts an inactive form of vitamin D into its active form, which is essential because we don’t get enough vitamin D from food alone. But the protection offered by vitamin D is far outweighed by the risk posed by UVA exposure.” 

The Indispensable Role of Sunscreen

Dermatologists continue to stress the importance of sunscreen in preventing skin damage. Sunscreens are formulated to block or absorb harmful UVB and UVA rays—the very wavelengths responsible for sunburn, DNA damage, and long-term skin aging. For example, broad-spectrum sunscreens with an SPF of 15 or higher have been shown to reduce squamous cell carcinoma by about 40 percent and melanoma by up to 50 percent. 

However, even the best sunscreens are not 100 percent effective. “Even when you reapply properly, you’re only getting about 90 percent protection,” Dr Zaidi noted. 

This means that a small percentage of UVB rays still reach the skin, which might be enough for some vitamin D synthesis.

Is a balanced sun-exposure the solution? 

Dr Zaidi explains that “there is no balanced sun exposure” that provides vitamin D without incurring some degree of UV damage. 

“We say not to get exposed to the sun whatsoever without protection," she advised.  "The negatives of unprotected sun exposure—ranging from premature aging to the risk of skin cancers—far outweigh any potential benefits of vitamin D synthesis from the sun." 

According to her, the most reliable way to ensure adequate vitamin D levels is through supplements and diet rather than deliberate sun exposure.

Also read: FACT CHECK: Should we be consuming multivitamins? - First Check