Sunscreen and vitamin D

sunscreen vitamin dDon’t avoid all sun exposure

Vitamin D just won’t get out of the news. I posted about it a couple of weeks ago, and here I am commenting again on something else I read.

Actually, a friend sent me a link to a health care blog that referred to a recently-published study out of Sweden. Swedish melanoma researchers followed almost 30,000 women (I’m not sure why just women) for 20 years and concluded:

We found that all-cause mortality was inversely related to sun exposure habits. The mortality rate amongst avoiders of sun exposure was approximately twofold higher compared with the highest sun exposure group… The results of this study provide observational evidence that avoiding sun exposure is a risk factor for all-cause mortality. Following sun exposure advice that is very restrictive in countries with low solar intensity might in fact be harmful to women’s health.

Most news sources succinctly paraphrased this to:

Women who avoid sunbathing during the summer are twice as likely to die as those who sunbathe every day.

Um, I’m not exactly sure that’s what the study is saying, so don’t rush to the nearest pool-side chaise lounge.

The researchers are looking at the possibility that sun avoidance leads to vitamin D deficiency, and that vitamin D deficiency leads to an increased risk of death, including a more aggressive form of melanoma.

But don’t overexpose yourself, either

I know we need sun on our skins to make vitamin D, an essential nutrient. And I’d much rather get vitamin D through sun exposure and fortified foods rather than supplements. In my other posts about vitamin D and sun protection, I suggest 15-30 minutes of unblocked UV rays every day. I frequently garden or go for walks or sit outside and don’t worry about slathering on the sunscreen.

But if I am planning on being outside for an extended period of time—boating, swimming, on the beach, etc.—I am diligent to use sunscreen. I don’t burn easily, but spend enough time outside and the UV rays will burn or damage your skin.

So I wasn’t really comfortable with how this study was being reported. Should I really avoid sunscreen altogether and roast myself in the sunshine? Knowing how Americans like to take things to extremes, will this start a new trend of thinking, “If a little sun exposure is good, even more will be a whole lot better!”

Related post: Protect your eyes from the sun

When I want a little more insight into some of these research studies, I often check out the blog The Incidental Economist. Aaron Carroll, MD, is a pediatrician. a health economist and a blogger. I trust his ability to interpret these papers, which are most often pages and pages of numbers—statistical gibberish to the uninformed eye.

As I suspected, he, too, had seen the results of the Swedish study and mainstream media’s reporting of it. Here is part of what he wrote:

There’s a lot of talk from this about vitamin D levels, and how this study shows that lack of sun leads to low vitamin D, and that’s a problem. Wow. First of all, the links of “low vitamin D” to death is a stretch. But even if you skip past that, there’s nothing in this study – and I mean nothing – that specifically looks at vitamin D. There’s no measurement of vitamin D. No way to know if anyone is vitamin D deficient. No vitamin D variables at all.

That tallies with my last post about the futility of screening for low vitamin D levels because there is currently no consensus on what is a low level, or how best to measure it, or if supplements really make a difference to health outcomes.

Dr. Carroll also stated:

This is not an RCT. [randomized control trial—the gold standard of research] There’s no causality here.

Causality means a direct cause and effect. For example, cigarettes cause lung cancer. Does this study show that low exposure to UV rays causes cancer or death? No. And perhaps those women getting more sun are just more active and spend more time outside, i.e. they have healthier lifestyles.

Dr. Carroll continues:

There are, however, RCTs showing that sunscreen prevents melanoma and skin aging.

I believe that everyone, including kids, should be outside playing. There are many, many pics of me doing so in my Instagram account. But I use sunscreen, and I use it liberally. Nothing in this study will change my mind about that.

This study hasn’t changed my mind, either. I will continue to use sunscreen when I think it’s necessary and not freak out when sunlight hits my unblocked skin on occasion.

Related post: Sunscreens – What works?

Sláinte!

Frugal Nurse

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