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Is lack of sunshine raising our blood pressure?

Kathleen Blanchard's picture
Exposure to UVA rays may be good for the heart.

It seems sunshine does something interesting to molecules in the skin to help promote cardiovascular health. Findings published in the Journal of Investigative Dermatology suggest sun exposure getting can lower blood pressure, which in turns translates to lower risk of heart, kidney and eye diseases as well as stroke.

Limiting sun exposure could mean higher rates of heart disease

According to scientists at the Universities of Southampton and Edinburgh, sunlight alters levels of the molecule nitric oxide (NO) that is abundant in the skin, delivering it to the circulation. NO dilates blood vessels to keep blood pressure lower.

Sunshine delivers nitric oxide to the body

Past studies have linked vitamin D's benefits to the action of nitric oxide in the body. The body synthesizes vitamin D from UVB rays. In the current study, researchers exposed 24 study participants to UVA rays from tanning lamps, twice, for 20 minutes. In one experiment UV rays were blocked and just heat from the lamps were used.

What the researchers discovered was that UVA rays dilate the blood vessels to "significantly" lower blood pressure without affecting vitamin D levels.

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Martin Feelisch, Professor of Experimental Medicine and Integrative Biology at the University of Southampton, comments: "NO along with its breakdown products, known to be abundant in skin, is involved in the regulation of blood pressure. When exposed to sunlight, small amounts of NO are transferred from the skin to the circulation, lowering blood vessel tone; as blood pressure drops, so does the risk of heart attack and stroke."

The researchers note heart attack and stroke rates are higher in the winter months when sunshine is less abundant.

Feelisch says it may be that getting a bit of sunshine each day has been overlooked as a heart healthy intervention.

"In future studies we intend to test whether the effects hold true in a more chronic setting and identify new nutritional strategies targeted at maximizing the skin's ability to store NO and deliver it to the circulation more efficiently," Feelisch said in a press release.

Skin cancer is a concern from sun exposure. But Feelisch suggests it may be time to take a fresh look at public health advice. Not being exposed to sunshine at all could be increasing our risk of cardiovascular disease. Boosting vitamin D levels with supplements has been "disappointing" Feelisch adds, with the exception of improving bone health.

The finding doesn't mean you should jump into the sun or go to a tanning bed to help lower your blood pressure. Skin cancer rates have soared in the past decade, making it important to interpret the study results with caution, at least for now. Headlines about the study stating sunbathing can lower blood pressure also aren't exactly accurate. The researchers used heated UVA lamps to find how the skin releases nitric oxide into the circulation to relax the blood vessels.

Journal of Investigative Dermatology (20 January 2014) | doi:10.1038/jid.2014.27