Let’s go through an evidence based review of what the science says regarding sun exposure and your health. We will answer questions including:
- Does sun exposure really increase skin cancer risk?
- Or, might sun exposure decrease risk of certain cancer, including skin cancer?
- What are guidelines for healthy sun exposure?
- When to use or not use sunblock.
- Can vitamin D supplementation be used in place of sun exposure?
Let’s jump in.
Dr. R’s Fast Facts
- Obtaining chronic, non-burning, sun exposure is a key practice for optimum health
- There are a wide range of health benefits from sun/UV exposure like various types of cancer, cardiovascular disease, Alzheimer disease/dementia, myopia and macular degeneration, diabetes and multiple sclerosis.
- Ideal Levels of Vitamin D: 40–60 ng/mL
- Vitamin D supplementation may not be an acceptable substitute
- Obtain at least 15 minutes (or more for darker skin type) of direct, unprotected, sun exposure 2-3 days a week, midday 11:00 AM – 3:00 PM, during the sunny months
- Sun exposure may protect the skin from cancer because sun exposure leads to the formation of the active form of vitamin D (1, 25-OH) which also improves DNA repair
- The Rise in Melanoma Incidence is Likely due to a combination of 2 factors:
- Less chronic, non-burning exposure to the sun (less time outside) -PLUS-
- Increased bouts of high exposure and burning (as occurs on vacations)
- A 20-year follow up study found avoiding the sun increase all-cause mortality
- Breast Cancer Incidence And Mortality
- One meta-analysis showed that higher blood levels of vitamin D were associated with decreased mortality
- Two studies have shown that increased sun exposure reduces breast cancer risk
- “John et al. 1999 found that women with higher solar UVB exposure in NHANES III had only about half the incidence of breast cancer as those with lower solar exposure.”
- “Knight et al 2007 found that increasing sun exposure from ages 10 to 19 reduced breast cancer risk by 35%, for the highest quartile of out-door activities vs. the lowest.”
- Non-Hodgkin’s Lymphoma, Colorectal, Prostate And Breast Cancer, And Multiple Sclerosis
- A systematic review concluded “in short sun exposure seems generally protective and the protective effects are sometimes independent of vitamin D levels or intake, meaning sun exposure exclusively appears to be responsible for the effect”
- Cardiovascular disease (CVD)
- Two studies have shown sun exposure helps to lower blood pressure, independent of vitamin D.
- “Liu et al. 2014 found that hypertension is reduced by UVR-induced nitric oxide independent of vitamin D. They showed that stores of nitrogen oxides in the human skin are mobilized to the systemic circulation by exposure of the body to UVA radiation, causing arterial vasodilation and a resultant decrease in blood pressure independent of vitamin D, conﬁrming the hypothesis of Feelisch et al. 2010”
- Obesity & Type II Diabetes
- Sun exposure but not vitamin D levels or supplementation reduced risk
- “Geldenhuys et al. 2014, found that UVR exposure levels, not vitamin D supplements or 25(OH)D levels, reduced the risk of obesity and type 2 diabetes…”
- Multiple Sclerosis
- “Baarnhielm et al. 2012 was an association study ﬁnding that persons with low UVR exposure had a signiﬁcantly increased risk of MS compared with those who reported the highest exposure (OR 2.2, 95% CI 1.5–3.3), and that this association persisted after adjustment for vitamin D status.”
- “Wang et al. 2014103 and Baarnhielm et al. 2012 conﬁrmed the conclusions of van der Rhee et al. 2013 that sun exposure reduces the risk of MS through pathways independent of vitamin D.”
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The Health Benefits of Sun Exposure
Dr. Michael Ruscio: Hi, this is Dr. Ruscio, and let’s talk about sun exposure and your health. Sun exposure is definitely an issue that seems to be clouded with confusion. And many people have probably heard recommendations, advising them to avoid the sun on the one hand. And on the other hand, heard about how important vitamin D is and know that sun exposure is one way to obtain vitamin D and may be a little bit confused in terms of how exactly do you broach this topic of sun exposure, vitamin D, and trying to optimize your health.
Because, and we’ll get into some details here in a moment, we’re learning that vitamin D supplementation is not a substitute for sun exposure, meaning that you cannot simply take vitamin D and derive all the health benefits that one could acquire from the sun. But what about skin cancer? Is that a risk from sun exposure? Well, let’s get into some of the details.
I’d like to review with you a paper—I’ll put the abstract up here on the screen—entitled, “The risks and benefits of sun exposure 2016.” So it’s an up-to-date review on sun exposure and how it affects your health. So let’s get through the dogma and fear-based recommendations and let’s look at what the science actually says.
So the main results here, and I’ll read a few quotes to start. “Studies that have shown a wide range of health benefit from sun/UV exposure. These benefits including, among others, various types of cancers, cardiovascular disease, Alzheimer’s disease, dementia, myopia and macular degeneration, diabetes, and multiple sclerosis.” So benefits meaning improvements in these diseases.
This review paper noted the ideal levels of vitamin D are between 40 and 60 nanograms per mL. And here’s an important quote. “It is apparent that vitamin D supplementation”—or supplements—“are not an effective substitute for adequate sun exposure.” And I can’t emphasize how important that is. Vitamin D supplementation has merit, has benefit, but it’s not a substitute for sun exposure.
And let’s get into a specific recommendation from the paper. “While people with type 2 skin”—this means people who burn very easily—”at 40 degrees latitude,” meaning not your… I guess you could say smack-dab in the middle of the United States. You’re not right near the equator which would be zero degrees. “Can obtain their annual requirements of vitamin D by spending about 15 minutes in the sun with face, arms, and legs exposed”—half that amount of time if you’re in a bathing suit—“two to three times a week.” Essentially in the middle of the day, during most months of May through October.
Now, again, remember, people with type 2 skin are people that burn easily. The darker your skin, the less prone you are to burn, the longer you need in the sun. What we’re seeing here is about 15 minutes a day, two to three days a week if you’re someone who has very sensitive skin. And we may be able to say that 20, maybe even 30 minutes two to three times a week for people with darker skin. I’m speculating there a little bit, but that certainly seems reasonable and in alignment with what other researchers are commenting.
So if you’re someone who doesn’t burn easily, like myself—I don’t burn very easily—I would aim for about 20 to 30 minutes in direct sun exposure with no sunblock two to three times per week. And I think that’s actually very reasonable.
Now, how does this break down to risk? So let’s look at melanoma, the most dangerous form of skin cancer. Nonburning sun exposure reduces the risk, while burning increases risk. And let me read a quote here. “It has long been observed that outdoor workers have a lower incidence of melanoma than indoor workers. A 1997 metanalysis found odds ratio of 0.86.” Odds ratio is an assignment of risk. If you’re above 1.0, depending on how the study is set up, you have an increased risk. If you’re below 1.0, you have a decreased risk.
So they found that chronic sun exposure, nonburning sun exposure, was associated with a decreased risk of—and this is via a metanalysis that they’re citing. And a metanalysis will look at the entire body or as much of the body of available evidence that’s possible and essentially go through some calculations to give this numeric representation of risk. So high-level science showing that the most dangerous form of skin cancer, melanoma, is protected by chronic, nonburning sun exposure.
Continuing here, they speculate that the reason why sun exposure may protect against skin cancer is because when sun hits the skin, the cholesterol in the skin is converted to vitamin D. And that vitamin D may have protective effects, especially on their DNA. And essentially, you may have this localized anti-cancer impact of vitamin D when sun hits your skin and the cholesterol in the skin is turned into vitamin D.
Now, the researchers also commented that the rise in melanoma is likely due to a combination of two factors. One, less chronic and nonburning sun exposure is obtained by most people. So people are getting less chronic time in the sun. With increased bouts of high exposure and burning. So you don’t spend much time in the sun, except for when you go on vacations or a weekend getaway or whatever it is. And you get way too much sun and have a higher predilection toward burning at that time.
Now, this is important because chronic sun exposure, nonburning, will allow you to get to know your skin and also condition your skin not to burn. Just like you condition a muscle not to be pulled or injured, you can condition your skin to tan and not burn.
And continuing here, “We find no consistent evidence that use of chemical sunscreens reduces the risk of melanoma.” Now, I should note there is some evidence showing sunscreens do reduce risk, but it’s not high-quality data. Now, is this to say that if you’re going to be in the sun for a long period of time you should not use a sunscreen? No, absolutely not. That’d be foolish, a foolish recommendation.
But what it does mean is that if you’re someone who is going to be walking from here to the store and back and you’ll be in the sun for 30 minutes total, you may not need to lather yourself with sunblock, put on long-sleeved clothing, a visor, and an umbrella. Because that level of avoidance may actually be bad for your health.
Now, what about non-melanoma skin cancer? So this is another form of skin cancer, usually comprised of squamous cell carcinoma and/or basal cell carcinoma. And this is more common, less deadly, but I should mention here that while nonburning exposure was associated with decreased melanoma risk, it was associated with an increase in non-melanoma skin cancer risk.
However, not all the data agree here. So there’s some contradictions in the data, but out of all the parameters that were examined, the only one that did seem to potentially be at an increased risk was a risk of non-melanoma skin cancer, squamous cell carcinoma, basal cell carcinoma. More common, less deadly than melanoma.
So when we look at skin cancer, there is some nuance. The less common, more deadly, more dangerous form—melanoma—is protected by chronic, nonburning sun exposure. Whereas, non-melanoma, you seem to be at an increased risk from exposure.
So if we run that kind of risk/reward, pro/con analysis, it looks like from the skin cancer perspective, reasonable chronic, nonburning sun exposure is probably not a bad idea. Now what about all-cause mortality? This is a measure of death from any cause. And when we look at this, we see that there is much association data showing that high blood levels of vitamin D are associated with lower all-cause mortality. But this isn’t perfect because what may be happening is healthier people have higher levels of vitamin D.
When someone has an illness, that illness may use up vitamin D. And so, when we say that people with low vitamin D die earlier or have a higher chance of death, it may not be the vitamin D. The vitamin D may be skewed, may be lower, secondary to a disease process that’s driving death. So we can’t really take a lot from that observation.
However, a 20-year follow-up study found that avoiding sun increased all-cause mortality. And I’ll quote here. “The mortality rate amongst avoiders of sun exposure was approximately two-fold higher compared with the highest sun exposure group.” We talked about this study awhile back, but that’s actually very important to know. And another study found that sun avoidance also increases all-cause mortality to a degree similar to smoking.
To quote: “Our findings that avoiding sun exposure was a risk factor for all-cause death of the same magnitude as smoking is novel.” So we definitely see some evidence that shows that avoiding the sun is bad for you from an all-cause mortality perspective. Regarding colorectal cancer, this group of researchers found no association or no consistent effect between sun exposure and colorectal cancer.
They did cite two studies that showed that increased sun exposure reduced the risk of breast cancer, and I’ll put two quotes in here for you for those. “Non-Hodgkin’s lymphoma, colorectal cancer, prostate cancer, breast cancer, and multiple sclerosis were all looked at together. And a systematic review concluded that essentially there seems to be protective effect for these diseases, independent of vitamin D levels or intake but is dependent upon sun exposure.”
Moving along to cardiovascular disease. “Two studies showed that sun exposure helps to lower blood pressure independent of your vitamin D levels.” Obesity and type 2 diabetes. “Sun exposure has been shown, but not vitamin D levels, to reduce risk of obesity and type 2 diabetes.” “A couple studies found that sun exposure helps reduce risk or protect against multiple sclerosis as type 1 diabetes has also been shown, as has liver disease.”
So the authors conclude “insufficient sun exposure has become a major public health problem, demanding an immediate change in the current sun avoidance public health advice. The degree of change needed is small but critically important. The public must be advised to obtain enough sun and vitamin D supplementation to maintain a serum level of vitamin D of at least 20 nanograms per mL.” But note, they’re not necessarily advocating vitamin D supplementation in this paper because they’re citing a number of studies showing that you can’t get there. You can’t get all the health benefits from sun exposure by replacing sun exposure with vitamin D supplementation.
And also, they say that the change needed is small. So sometimes people have a hard time with nuance, meaning if your old belief was that the sun was bad for you because it causes skin cancer, you may have a hard time considering getting sun exposure a few days of week because you’re picturing in your head going to this extreme of slathering on suntan lotion and spending an hour in the sun every day or five days a week which would be going to the other extreme.
So we shouldn’t go to extremes here. We just realize that a few days a week, obtaining maybe 15-30 minutes in the sun, direct exposure during the middle of the day without any protection is a healthy practice. And we’ve covered a number of conditions and diseases and even your overall chance of death that will be helped in a beneficial way from chronic, nonburning sun exposure.
So your wrap-up takeaways: obtaining chronic, nonburning sun exposure is a key practice for optimum health; vitamin D supplementation may not be an acceptable substitute; and obtain at least 15 or more minutes, if you have darker skin, of direct, unprotected skin exposure two or three days a week, midday during the sunny months.
And hopefully, this video that’s reviewed a review paper on sun and broken out the specific diseases and conditions that may be impacted by the sun helps you have a little bit more confidence in the fact that you should be spending a few days per week getting sun exposure without sunblock. Now, when you’re going to have an extended period of exposure to the sun, protect yourself, of course. Don’t be foolish. Do not burn.
But hopefully, again, all of this information helps you get healthy, get back to your life, and have a more reasonable relationship and perspective on sun exposure. All right. Thanks.
What do you think? I would like to hear your thoughts or experience with this.
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Dr. Ruscio is your leading functional and integrative doctor specializing in gut related disorders such as SIBO, leaky gut, Celiac, IBS and in thyroid disorders such as hypothyroid and hyperthyroid. For more information on how to become a patient, please contact our office. Serving the San Francisco bay area and distance patients via phone and Skype.