The human body is a complex system.
We don’t understand how its gazillion parts fit together.
We do know that sunburns are bad for us, and that even in the absence of sunburns, there’s such a thing as “too much sun”. We also know that getting some sunlight in the middle of the day is beneficial, and we know ways to mitigate both getting skin cancer and dying from it. We also know that most sunscreens are decidedly iffy, that a tan provides some protection against solar radiation, and that sudden blasts of insolation seem to be much more problematic than a continuous building-up of sun exposure. (On that last point: People who work outdoors have been shown to have lower skin cancer rates; a recent study of skin cancer rates found higher rates in northern (US) states; and wintertime sun-vacations correlate with higher skin cancer rates.)
It seems reasonable, then, to get enough but not too much sun in the middle of most days, to avoid sunburns, to prefer shade and covering over sunscreen, to build up your tan gradually each spring, and to avoid trips that swing your sun exposure from 0 to 100 (ie: Don’t Travel From Canada to the Bahamas in February!).
Below we’ll list some links to support the above guidelines, but the principle needs no links: We evolved in sunlight. And medical science always knows way less than it thinks it knows: it’s not going to figure out what all you lose by hiding from the sun; nor is it going to figure out how to balance all those losses with its various potions.
Sunlight: Go easy, but don’t pretend you’re a blind albino salamander designed to live your life cycle in pitch black. Obviously, if you are an albino human, you’re sunlight calculations are different than other people’s. We’ll talk a little bit about how much sun various skin types should receive in the below links, but albinism is a special case we’ll not here address.
For people who tan without burning: Maybe like ten minutes a side in the middle of the day several days a week while the sun is high enough to make a difference (April-September if you live above 40 degrees North or below 40 degrees South). Otherwise stick to the shade and wear a wide-brim hat
Also: Enough with all the showering! Who knows how it all fits together, but surely the human body was not designed to wash skin oils off every day! For one thing, the vitamin D needs some time to stew in the oil to foment its helpful contribution.
Maybe a shower every other day, with soap only where you need it (smelly areas). Or maybe just quit showering all together. At any rate, don’t take a shower right after you’ve been in the sun: those oils protect your skin.
Related: Deodorant? Really? Chemicals in your armpits? For what?
Author: Who knows?
Editors: B Willard & A Whistletown
Copyright: AM Watson
[8/9/2020: Sometime this week we’ll add the links]
Badness of sunburns:
“Double your risk of potentially deadly melanoma with a history of five or more sunburns” – skincancer/org
“Getting a sunburn just once every two years can triple your risk of melanoma skin cancer” – cancerresearchuk.org
Sunlight in the middle of the day for Vitamin D production
“A simple test is to look at your shadow. If its the same height or shorter than you, you’re getting enough sun to make vitamin D. If its longer than you, you’re probably not. In most places in the US in the winter, you can probably guess what you’re going to see.” – linuspaulinginstitute
“Except during the summer months, the skin makes little if any vitamin D from the sun at latitudes above 37 degrees north (in the United States, the shaded region in the map) or below 37 degrees south of the equator. People who live in these areas are at relatively greater risk for vitamin D deficiency.” – health.harvard.edu
Sunlight on your skin for nitric oxide release / cardiovascular health:
” In this issue, Liu et al. (2014) show that UVA decreases blood pressure and increases blood flow and heart rate in humans, which is beneficial to the cardiovascular system. This is likely mediated by UVA causing release of nitric oxide (NO) from skin stores. This mediator may have additional effects on human health” – sciencedirect
Sunlight & BDNF for brain health:
“Some liken BDNF to a ‘fertilizer for your brain’ because it helps to prevent the death of existing brain cells and stimulates the growth of new ones, supporting brain function in many ways. Low levels of BDNF are linked to anxiety, depression,2 obesity,3 Schizophrenia4 and Alzheimer’s Disease.5”
“In a Norwegian study of 2851 people, levels of BDNF directly correlated with hours of sun exposure in both men and women, levels dropped when hours were reduced.7”
[also helpful for BDNF production: High Intensity Interval Training, Mediterranean Diet, Intermittent Fasting, Cold, Less Stress]
But I can’t figure out if it is just that the eyes need to see sunlight, or what.
Problems with Suncreens:
“Since scientists don’t know for certain whether sunscreen alone can help prevent melanoma, EWG strongly disagrees with the FDA’s decision to allow sunscreen makers to claim their products prevent cancer.”
Most US sunscreens block UVB, but UVA also causes skin cancer, and it is much more prevalent.
“Avobenzone and zinc oxide are the two best UVA filters in American sunscreens, providing the desired protection from free radical formation, and titanium dioxide is moderately effective at protecting against UVA rays. Yet even they are far from perfect. UV rays can break down avobenzone, although it’s almost always mixed with a stabilizer to slow down the process.”
“In the absence of truly protective regulations, consumers are in the worst possible position – likely to think their sunscreen is providing more protection than it is, then staying out in the sun longer, thereby increasing their risk of skin cancer and skin damage.”
EWG (Environmental Working Group)
“Bloodstream levels of four sunscreen chemicals increased dramatically after test subjects applied spray, lotion and cream for four days as directed on the label, according to the report.
“The levels far exceed the FDA-set threshold which require topical medications to undergo safety studies, said Dr. Kanade Shinkai, a dermatologist with the University of California, San Francisco School of Medicine.”
Article also discusses possible effects on hormones.
2019 article by D. Thompson for WebMD
Evidence that sunscreen is safe and useful
“An analysis published in 2011 looked at studies dating back to the 1960s and also found no negative health effects of sunscreen use.”
The famous Australian study:
“In a community-based randomised trial with a 2 by 2 factorial design, individuals were assigned to four treatment groups: daily application of a sun protection factor 15-plus sunscreen to the head, neck, arms, and hands, and betacarotene supplementation (30 mg per day); sunscreen plus placebo tablets; betacarotene only; or placebo only. Participants were 1621 residents of Nambour in southeast Queensland, Australia. The endpoints after 4·5 years of follow-up were the incidence of basal-cell and squamous-cell carcinomas both in terms of people treated for newly diagnosed disease and in terms of the numbers of tumours that occurred. …”
“There were no significant differences in the incidence of first new skin cancers between groups randomly assigned daily sunscreen and no daily sunscreen …”
“Similarly, there was no significant difference between the betacarotene and placebo groups in incidence of either cancer …”
“In terms of the number of tumours, there was no effect on incidence of basal-cell carcinoma by sunscreen use or by betacarotene but the incidence of squamous-cell carcinoma was significantly lower in the sunscreen group than in the no daily sunscreen group …”
Daily sunscreen application and betacarotene supplementation in prevention of basal-cell and squamous-cell carcinomas of the skin: a randomised controlled trial
A note on this Australian study everyone’s always quoting:
The daily use of sunscreen reduced squamous-cell carcinomas, but not basal-cell carcinomas. It doesn’t mention melanomas.
Melanoma is the most dangerous type of skin cancer.
“Sunscreen isn’t a magic shield. The National Cancer Institute (NCI) says the evidence that it prevents squamous cell skin cancer is only “fair.” (For basal cell cancer and melanoma, the NCI says there is inadequate evidence to know if sunscreen is preventive.) In fact, some argue that by preventing sunburn, sunscreens offer a false sense of security, encouraging people to stay in the sun too long. Sunscreen users should buy one with a sun protection factor (SPF) of at least 15. Be sure to put on enough lotion. You need almost three tablespoonfuls on your face, neck, arms, trunk, and legs per application. At least a teaspoon should go on your face and neck.”
health.harvard.edu (they recommend avoiding the sun from 11AM to 4PM, but that’s the time when your skin makes Vitamin D; that’s why we think: just get like ten minutes a side from 11AM to 4PM and then head to the shade.)
States with Highest skin cancer rates:
“Utah, Delaware, Vermont, Minnesota and Idaho have the highest skin cancer rates of all U.S. states, and their residents are at higher risk for melanoma than those in Florida, California or Texas, according to the CDC.”
“‘Many of the high-risk states have intermittent sun exposure,’ says Charles Komen Brown, Medical Director of Surgery & Surgical Oncologist at our Chicago hospital. ‘People who are not used to regular sun exposure are at risk for getting sunburned when they experience sunny days. Any sunburn predisposes them to getting any kind of skin cancer, including melanoma.'”
A note on Idaho: Most people live in and around Boise. It is a semi-desert and at high altitude. So there you do get a lot of sun on your nose in the summer. I regret not wearing a hat more often while living in Boise, ID.
Lower skin cancer rates for outside workers / call for a tan without burning:
Solar radiation calculator (accounting for skin type, latitude, etc):
How much sunlight do you need?:
Why the radiation needs to be in the middle of the day:
Why you can’t make Vitamin D from sunlight for half the year at northern latitudes:
Diet to reduce skin cancer rates:
Mole checks to reduce skin cancer mortality:
What about storing up vitamin D for the winter:
Different races have different relationship to vitamin D & solar radiation?:
Showering is stupid:
Complexity of the system: Vitamin D, Vitamin K, Vitamin A balance: