uvb map

Radiation from the sun causes the production of vitamin D when it interacts with human skin, so there’s reason to think that getting sunshine is healthy.

Just how healthy?

More sun means longer life

Check out the following graph, which comes from a paper, “Skin cancer as a marker of sun exposure associates with myocardial infarction, hip fracture and death from any cause”.(1) Skin cancer is the result of many years of exposure to the sun.
skin cancer death

If a person has skin cancer, his odds of getting a hip fracture, a heart attack, or dying from any cause drop dramatically.

Skin cancer (non-melanoma) cut the death rate nearly in half – odds ratio 0.52. That figure was substantially attenuated when adjusting for age and calendar year (to account for changes in cancer treatment), but still significantly lower for those who ever had skin cancer versus those who didn’t.

Way back in 1937, it was discovered that sailors in the United States Navy had about 8 times the rate of skin cancer as other men of the same age, but only about 40% of the rate of other cancers.(2)

While non-melanoma skin cancer is a readily treatable disease with a fatality rate of under 1%, and accounts for about 1% of all cancer fatalities, other cancers have a total fatality rate of around 50%.

The following graph shows the rate of death from cancer in white men from 1970 to 1994 as a function of the amount of solar radiation where they lived.(3) The date of the determination of solar radiation was July, 1994.

radiation cancer


It can be seen that death rates from cancer drop very low with lots of solar radiation. The following map gives an idea of the amount of solar radiation that correlates with the above chart.


uvb map

The “10” on the upper chart of cancer mortality vs UV-B radiation corresponds about to northern Chile on the map. The southwestern U.S. might be 7 or 8.

Finally, a recent study showed the power of sunlight: “Avoidance of sun exposure as a risk factor for major causes of death: a competing risk analysis of the Melanoma in Southern Sweden cohort”.(4) The study found that women with “active sun exposure habits” had a longer life expectancy, and that the degree to which sun helped their health was comparable to not smoking.

Nonsmokers who avoided sun exposure had a life expectancy similar to smokers in the highest sun exposure group, indicating that avoidance of sun exposure is a risk factor for death of a similar magnitude as smoking. Compared to the highest sun exposure group, life expectancy of avoiders of sun exposure was reduced by 0.6–2.1 years.

It might be thought that some or all of the results were confounded by socioeconomic factors; for instance, people who can afford sun-drenched vacations might have better health habits or genes, and this is the source of their better health. However, when the first study cited above on skin cancer and mortality was adjusted for level and length of education, which are proxies for IQ and income, the association between lower death rates and skin cancer barely budged. (See table.)

While the association between solar radiation and better health is likely due all or in part to vitamin D, solar radiation itself can’t be ruled out as causative, since low-level radiation is hormetic, meaning it’s a stress that causes the body to increase cellular defense mechanisms.

As with any form of hormesis, too much of the stress can be damaging. Therefore, moderate exposure is to be aimed for.

While moderate solar exposure improves health, sunburns should be avoided, as these are associated with skin cancer. Length of time that one should be exposed to the sun vary greatly according to time of day, season, and latitude, and also amount of clothing and skin color of the person. See this article at the Vitamin D Council for guidance on sun exposure.

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  1. Very interesting. I spend a lot of time in the sun, and try to maintain a deep tan. It’s just anecdotal, but I’ve noticed a lot of the really old people I encounter around here tend to be tan and active outdoors (tennis, walking, swimming, lawn bowling). Also, I remember reading somewhere years ago that it’s better to maintain a deep tan year round rather than getting intermittently burned.

  2. Scott says:

    Welp I guess those of us who live in Seattle are screwed!

  3. Weltanschauung says:

    So sunshine is hormetic, along with broccoli and heavy lifting. Hew about tobacco?

  4. Joshua says:

    The health benefits of good ol’ sunshine is almost certainly extend beyond just vitamin D. I’ve read elsewhere that one of the main benefits of sun exposure is that it stimulates production of nitric oxide in the body, which improves circulation and may have other benefits. The only caveat is that it seems sun exposure does increase skin wrinkling with age. It seems it’s a trade-off…but I figure better to live longer and maybe be a bit more wrinkled (and bronzed!) then die earlier.

  5. ted says:

    I’ve read an interesting take on Vitamin D: https://gettingstronger.org/2012/11/why-i-dont-take-vitamin-d-supplements/

    The part about 1,25-D (active vitamin D) vs 25-D(inactive) was very interesting.
    Also, blood tests for vitamin D look at 25-D, i.e. inactive form. There is a possibility that we don’t have the science right about Vitamin D, and supplementation with D3 does not raise active D3, and may reduce body’s production of active D3. Like when you take exogenous T, testicles stop producing endogenous T. Vitamin D is a hormone after all.

    Very interested to hear your thoughts on this.

  6. Jason says:

    Having a non-melanoma skin cancer is probably a big wake up call for improving your health and also a prompt for reducing unprotected sun exposure.

  7. alf says:

    So… Don’t use sunscreen?

    • P. D. Mangan says:

      Some of the compounds in sunscreen can be toxic, so I’d say don’t use it regularly, but only when exposed to sun for long periods. Also, many many people report they no longer get sunburned when they stop ingesting seed oils.

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