A few weeks ago I was at a conference in Tuscon, Arizona. Two things really surprised me while I was there. First, quite a few people ordered egg-white omelets for breakfast. Huh? Didn’t they get the memo that dietary cholesterol doesn’t increase the risk of heart disease, or even raise blood cholesterol levels? Egg-white omelets are so 1995!
Second, I noticed that a number of people were slathering themselves with sunscreen and wearing long sleeve and pants or wide-brimmed hats every time they stepped out the door in order to avoid the sun.
This kind of “sun phobia” is the unfortunate—but inevitable—result of national guidelines in many countries over the past 30–40 years advising strict restriction of sun exposure.
Too much sun exposure isn’t a good thing, but not enough may be even worse. Read this to find out why.
These guidelines were based on the observation that light-skinned people of European ancestry living in Northern Australia had the highest risk of malignant melanoma, the deadly form of skin cancer, in the world. However, as you’ll see below, applying guidelines that were originally developed for people living in an area with a high ultraviolet (UV) index, such as Northern Australia, to areas with limited sunshine and a much lower UV index (such as many parts of North America and Europe) is not only unnecessary, it may be harmful.
Not enough sun exposure may be just as harmful as too much
In a new study, researchers tracked the sun exposure habits of 30,000 Swedish women for 20 years. They found that the women who strictly avoided the sun during that period had a two-fold greater risk of early death than women who received normal amounts of sun exposure.
What’s more, they found that women with normal sun exposure habits were not at significantly increased risk for malignant melanoma or melanoma-related death. (1) This is consistent with the results of a previous Swedish study that followed 38,000 women for 15 years and found that sun exposure was associated with reduced risk of both cardiovascular and overall death. (2)
I’d like to emphasize that these studies are observational in nature, and thus do not prove causality. It’s possible that the women who got more sun had healthier diets and lifestyles than those who avoided the sun, and those factors led to the lower mortality, rather than the sun exposure.
However, it’s also possible—and probable, in my opinion—that completely avoiding does increase the risk of death. There are several possible mechanisms that explain why:
One of the primary benefits of sunlight is its ability to stimulate vitamin D production. Vitamin D deficiency is a major predisposing factor in at least 17 varieties of cancer, as well as heart disease, stroke, hypertension, autoimmune disease, type 2 diabetes, depression, birth defects, infectious disease and more. (3) It’s not a stretch, therefore, to imagine that women who avoid the sun have lower vitamin D levels (especially in areas with limited sun, like Sweden) and thus a higher risk of death.
Scientists observed a connection between sunlight and cardiovascular disease as far back as the 1970s, when clinical trials on hypertension showed that blood pressure was consistently lower in summer than winter. (4) Later studies showed that the both the prevalence of hypertension and average blood pressure is directly correlated with latitude; in other words, those living at northern and southern latitudes (with less sunlight) had more hypertension and higher average blood pressure, while those living closer to the equator had less hypertension and lower average blood pressure. (5)
Clinical experiments have also provided direct evidence that ultraviolet light reduces blood pressure. In one study, researchers exposed one group of people to lamps that gave off ultraviolet light as well as heat, and another group to lamps that only gave off heat. In the group that received both heat and ultraviolet light, blood pressure dropped significantly after just one hour of exposure. (6)
How does sunlight lower blood pressure and reduce the risk of cardiovascular disease? Sunlight stimulates the production of a chemical called nitric oxide in our skin. Nitric oxide helps our blood vessels to relax and expand, which in turn reduces blood pressure. This is important because high blood pressure is one of the strongest risk factors for cardiovascular disease, and even relatively small reductions in blood pressure can dramatically reduce the deaths from both heart attack and stroke.
For example, a drop of 20 mmHg in systolic blood pressure (blood pressure is expressed as a fraction, i.e. 120/80, and “systolic” refers to the number on the top) leads to a two-fold reduction in the overall risk of death in both men and women between the ages of 40 and 69. (7)
Sunlight may also reduce the risk of cardiovascular disease—and by extension, the risk of death—by putting the brakes on inflammation. (8) These beneficial effects of sunlight are likely to extend to other organs and tissues as well, since both blood pressure and inflammation have widespread effects in the body.
Another effect of sunlight that isn’t mediated by vitamin D is its ability to regulate immune function. Studies have shown that the the more hours of sun there are where you were born, the lower the risk you’ll develop multiple sclerosis. (9) Along the same lines, the more exposure to sun people have where they work and live as adults, the lower their rates of MS, and relapse rates for MS are higher in winter than in summer. (10) Evidence for benefit from sunlight is strong for other autoimmune diseases as well, such as type 1 diabetes.
Exposure to sunlight may improve endocrine function, elevate mood (via its effects on certain brain chemicals like serotonin) and increase DNA repair capacity, all of which could conceivably extend lifespan. (11)
The “Goldilocks” effect: How much sun exposure is “just right”?
With all of this in mind, how much sun exposure is “just right”? How can we minimize our risk of skin cancer while optimizing vitamin D levels and getting the additional cardiovascular and immune benefits of sunlight?
Just follow these guidelines for you and your family members:
- If you have fair skin, aim for spending about half the amount of time in the sun that it takes for your skin to turn pink (without sunscreen) two to three days a week. This could be as little as 10 minutes for those with very fair skin. If you have dark skin, you may need up to two hours per day to generate the same amount of vitamin D (which is why supplementation may be necessary for those with darker skin).
- Never burn yourself in the sun. Cover yourself with light clothing, wear a hat, shade yourself with an umbrella, tree or canopy, wear sunglasses, and/or use a safe sunscreen to prevent sunburn if you’re going to be exposed to sunlight for a prolonged period. (But see the section below for important information about sunscreen.)
- Pay attention to the time of day, latitude and season. This probably goes without saying, but you need less sun exposure at mid-day during the summer on the equator to generate a given amount of vitamin D than in the late afternoon during the winter in New York City. Vary your exposure accordingly.
- Infants under 6 months old don’t have much of the protective pigment (melanin) in their skin. It’s best to avoid direct sun exposure at mid-day, use protective clothing and a hat, and limit exposure to the morning or late afternoon hours. Infants may be particularly susceptible to the toxic effects of some sunscreen ingredients, so use clothing or shade when possible.
Sun protection is important if you plan to be out in the sun for a long enough time to get burned, but most sunscreens on the market are not beneficial or even safe. Stephan Guyenet explains on his blog how typical sunscreen fails to prevent melanoma, the deadliest form of skin cancer. Most commercial sunscreens have a slew of chemical ingredients such as fragrances, parabens, alcohols, chemical solvents and petroleum oils that break down when exposed to sunlight.
Unfortunately, even natural sunscreen materials like zinc oxide could be problematic. (12) Researchers have recently discovered that, in vitro, zinc oxide may generate free radicals when exposed to UV radiation, which could damage cells and raise the risk of cancer. (13) More testing needs to be done, but this preliminary research shows that even natural sunscreen ingredients could have unforeseen consequences to your skin health. Until we know more, however, using a natural, mineral based sunscreen is still a better choice than the chemical sunscreens that are commonly available.
Ultimately, the best way to protect yourself from melanoma—while ensuring you still get the benefits of sun exposure—is to tan gradually, without burning.
It’s entirely possible that public health recommendations that significantly restrict sun exposure may be doing more harm than good in regions with limited sunshine and a low UV index, such as many parts of Europe, the UK, and North America. Yet many people are unaware that the advice they’ve been given about avoiding sun exposure doesn’t reflect the current scientific evidence on this topic.
This reminds me of the situation we’re in with dietary fat and cholesterol. The mainstream media and medical establishment spent decades scaring us away from egg yolks, cheese, meat, and other high-fat, high-cholesterol foods. The result of this advice was an increase in the consumption of highly refined carbohydrates—which, ironically, contributes to the epidemics of metabolic and cardiovascular disease that fat and cholesterol restriction was supposed to address.
As I mentioned in a recent podcast, the current evidence suggests that (on average) dietary cholesterol and saturated fat do not affect blood cholesterol levels or increase the risk of heart disease. Yet I think it’s safe to say that most people still perceive a breakfast of cold cereal, toast, and OJ to be “healthier” than bacon and eggs. It took years to convince people that natural fats found in real foods are bad for them, and unfortunately it’s probably going to take years to relieve them of the burden of that misunderstanding.
I’m afraid the same will be true for sun exposure. I often see parents putting sunscreen on their kids as soon as they step out the door, or adults that wear long sleeves and big hats whenever they go outside. Current research doesn’t support this, but I think it’s going to take a while for the public policy to change and the message to get out. (Though you can help speed that along by sharing this article with people you know that are still sun-phobic.)
Now I’d like to hear from you. How much sun do you get? Has your attitude about sun exposure changed in the last few years? What about the attitude of your friends and family? Let us know in the comments section.
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