Sunscreen and supplements can lower your vitamin D levels

As Australia gets ready for summer, we’re sure to receive plenty of messages about the importance of sunscreen for preventing sunburn and skin cancer. But a landmark population health study led by QIMR Berghofer has now complicated things, finding that people who used SPF50+ sunscreen daily for about a year were more likely to be vitamin D deficient than those who used it less frequently.

The study from the Sun-D Trial involved 639 participants who were not regular sunscreen users. Half were instructed to apply SPF50+ sunscreen daily for a year (excluding winter in southern regions), while the other half served as a control group. The results, as published in the British Journal of Dermatology, found that 46% of the sunscreen group were vitamin D deficient after 12 months, compared to 37% in the control group.

Vitamin D plays a role in bone health and immune function, and may also influence other health outcomes. But while UV radiation from the sun is the most natural way to get vitamin D, this also increases skin cancer risk, especially in Australia. Therefore, the researchers advise people to continue using SPF50+ sunscreen regularly — especially when the UV index is forecast to reach at least 3 — and to consider other sources of vitamin D such as diet and supplements.

“Sunscreen remains a cornerstone of skin cancer prevention, backed by decades of robust evidence,” said Professor Rachel Neale, lead investigator of the Sun-D Trial. “Our findings simply suggest that people who are diligent about daily sunscreen use may want to consider vitamin D supplementation as a safe, effective and cheap way to maintain healthy vitamin D levels.”

But it turns out that supplementation might not be all that simple, as separate research out of the UK has found that taking vitamin D₂ supplements can lead to a drop in the body’s concentration of vitamin D₃, which is the form our bodies naturally produce from sunlight and use most effectively to raise overall vitamin D levels.

The researchers from the University of Surrey, John Innes Centre and Quadram Institute Bioscience analysed data from randomised controlled trials and found that vitamin D₂ supplementation resulted in a reduction in vitamin D₃ levels compared to those not taking a vitamin D₂ supplement. In many of the studies, the vitamin D₃ levels went lower than in the control group. Their findings were published in the journal Nutrition Reviews.

“Vitamin D supplements are important — especially between October and March, when our bodies cannot make vitamin D from sunlight in the UK,” said lead researcher Emily Brown, a PhD research fellow at the University of Surrey. “However, we discovered that vitamin D₂ supplements can actually decrease levels of vitamin D₃ in the body, which is a previously unknown effect of taking these supplements. This study suggests that subject to personal considerations, vitamin D₃ supplements may be more beneficial for most individuals over vitamin D₂.”

The research supports a previous study published in Frontiers in Immunology, led by the University of Surrey’s Professor Colin Smith, which suggests that vitamin D₂ and D₃ do not have identical roles in supporting immune function. Vitamin D₃ has a modifying effect on the immune system that could fortify the body against viral and bacterial diseases.

“We have shown that vitamin D₃, but not vitamin D₂, appears to stimulate the type I interferon signalling system in the body — a key part of the immune system that provides a first line of defence against bacteria and viruses,” Smith said. “Thus, a healthy vitamin D3 status may help prevent viruses and bacteria from gaining a foothold in the body.”

The scientists concluded that further research into the different functionalities of vitamin D2 and D3 should be a priority in deciding whether vitamin D₃ should be the first-line choice of vitamin D supplement, subject to individual requirements.

Image credit: iStock.com/GO