UV Light Provides a Multitude of Health Benefits

Story at-a-glance

  • The evidence clearly shows that once you reach a serum vitamin D level of 40 ng/ml, your risk for cancer plunges by 67 percent, compared to having a level of 20 ng/ml or less
  • When sunlight shines on your skin, nitric oxide—a blood pressure lowering compound—is released into your bloodstream, which helps protect your cardiovascular system and cut your risk of heart attacks and stroke
  • Other health benefits of sensible sun exposure include eye health, sexual health, improved mood and mental health, reduced risk for autoimmune diseases and certain genetic disorders, and a reduced risk of death from any cause


This is an older article that may not reflect Dr. Mercola’s current view on this topic. Use our search engine to find Dr. Mercola’s latest position on any health topic.

By Dr. Mercola

If there's one thing we require to thrive it is sensible exposure to the sun. Sure, sunlight is needed for growing food, but you also need direct sun exposure to thrive, just like plants.

The video above features a 2014 lecture by German doctor Alexander Wunsch, M.D. In it, he provides a historical perspective on sun exposure, explaining why current sun avoidance recommendations may be doing far more harm than good.

For starters, spending time in bright mid-day sun helps anchor your circadian rhythm, helping you sleep better.

Surprising as it sounds, scientists have even found vitamin D deficiency raises your risk of obstructive sleep apnea.1 In one study, 98 percent of patients with sleep apnea had vitamin D deficiency, and the more severe the sleep apnea, the more severe the deficiency.

Vitamin D is produced in your skin when exposed to direct sunlight, and the importance of vitamin D has become increasingly well-recognized.

The overall health benefits of vitamin D are so significant, a Swedish research team recently warned that "avoidance of sun exposure is a risk factor for death of a similar magnitude as smoking."2,3

A growing number of studies also reveal there are benefits to sun exposure that are completely unrelated to vitamin D production — findings that clearly support the notion that the human body evolved to not only survive, but to thrive, in sunlight.

May Is National Sunshine Month

To boost public awareness of the importance of sunshine to human health, GrassrootsHealth has declared May as "National Sunshine Month." According to a May 5 press release:4

"Missing sunlight puts us at serious risk of a multitude of dangerous health problems," said Carole Baggerly, Director of GrassrootsHealth. "It is essential that we improve public understanding of the need for sunshine exposure and health outcomes."

Over the next four weeks, GrassrootsHealth's experts within the medical and scientific community will educate the public and those in the medical and healthcare fields on why the sun is essential for public health.

This will include the launch of GrassrootsHealth's newest program "Harness the Power of the Sun for Health," which will provide software for individuals to assess their current situation, set sunshine goals and track vitamin D levels and health outcomes.

"Advice from some within the medical community, and even our own government, encouraging Americans to avoid the sun is an immense threat to human health," said Baggerly. "We expect National Sunshine Month will raise awareness of the sunshine, its many health benefits and ways to take advantage of it."

Harness the Power of the Sun for Health Infographic Preview
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Vitamin D Slashes Cancer Risk

The evidence now clearly shows that once you reach a serum vitamin D level of 40 ng/ml, your risk for cancer plunges by 67 percent, compared to having a level of 20 ng/ml or less.5,6,7,8,9,10,11

Even the Health and Medicine Division (HMD) of the National Academies of Sciences, Engineering, and Medicine (formerly Institute of Medicine, IOM) has reported an association between vitamin D and overall mortality risk from all causes, including cancer.12,13

Vitamin D also increases your chances of surviving cancer if you do get it,14,15 and this includes melanoma patients.16,17

Higher Vitamin D Improves Body Composition

Vitamin D is also important for your bone health, cognitive function, immune function, and healthy pregnancy and infant development.18 According to Canadian researchers, there's a "clear correlation to adequate availability to vitamin D and body structure in babies."

Besides boosting bone density, which was expected, they were surprised to discover that infants given up to 1600 IUs of vitamin D per day during the 12 months of life also had greater muscle mass and less fat at age 3, compared to those who received the daily amount of 400 IU's a day.19,20

Despite their surprise, several other studies have confirmed the link between vitamin D deficiency, abdominal obesity and visceral fat, and vitamin D levels tend to be low in obese individuals of all ages.

Sun Exposure Increases Nitric Oxide Production

As recently reported by The Daily Mail,21 "Even taking the skin-cancer risk fully into account, [scientists] say that getting a good dose of sunshine is statistically going to make us live longer, healthier and happier lives."

Research has shown that when sunlight strikes your skin, nitric oxide (NO) is released into your bloodstream.22 NO is a powerful blood pressure lowering compound that helps protect your cardiovascular system, cutting your risk for both heart attacks and stroke.

According to one 2013 study,23,24 for every single skin cancer death, 60 to 100 people die from stroke or heart disease related to hypertension. So your risk of dying from heart disease or stroke is on average 80 times greater than your risk of dying from skin cancer.

While higher vitamin D levels correlate with lower rates of cardiovascular disease, oral vitamin D supplements do not appear to benefit blood pressure, and the fact that supplements do not increase nitric oxide may be the reason for this. According to researcher Dr. Richard Weller:

"We suspect that the benefits to heart health of sunlight will outweigh the risk of skin cancer. The work we have done provides a mechanism that might account for this, and also explains why dietary vitamin D supplements alone will not be able to compensate for lack of sunlight."

To understand how UV light affects your cardiovascular function, you can also review Dr. Weller's paper "Sunlight Has Cardiovascular Benefits Independently of Vitamin D."25 One of the key messages presented in this paper states that:

"All-cause mortality should be the primary determinant of public health messages. Sunlight is a risk factor for skin cancer, but sun avoidance may carry more of a cost than benefit for overall good health."

Sunlight Modulates Genetic Expression Related to Inflammatory Response

Dr. Weller has also pointed out that sunlight appears to alter genetic expression, noting that: "Last year, Cambridge University scientists showed that the expression of 28 percent of our entire genetic make-up varies from season to season."26

Some of those genetic changes affect your inflammatory responses. During winter months, inflammatory immune-system genes are activated, which helps combat infectious microbes, and during the summer the activity of anti-inflammatory gene activity increases.

In essence, during the summer your body begins to combat the damage incurred by the inflammation produced when your immune system is on red alert. But for that, you need sun exposure.

UV Light Is a Potent Anti-Infective

Both UV light itself and the vitamin D produced when your skin is exposed to it have potent antimicrobial  effects. Vitamin D from sun exposure increases your body's production of naturally occurring antimicrobial peptides that destroy the cell walls of viruses and bacteria.

Sun exposure also increases blood levels of infection destroying lymphocytes (white blood cells). Besides boosting rates of cardiovascular disease, widespread sun avoidance may also be responsible for the reemergence of tuberculosis (TB), which now kills about 4,100 people every single day.27

In 2014, there were 1.5 million TB-related deaths worldwide, making it the No. 1 infectious disease out there. Compare that to the 55,100 who die from melanoma each year (worldwide).

Studies have shown that metabolizing vitamin D can restrict the growth of tuberculosis within cells,28 and Indonesian scientists found that treating tuberculosis patients with 10,000 units of vitamin D daily led to a 100 percent cure rate!29 There's even evidence to suggest vitamin D may be effective against drug-resistant TB.30

UV light, especially blue light, also acts as a potent disinfectant of your environment. Research has found UV light can reduce the spread of tuberculosis in hospital wards and waiting rooms by 70 percent,31, 32 and helps kill 90 percent of drug-resistant bacteria in hospital rooms.33 Data suggests UV light at 254 nm can kill drug-resistant strains of S. aureus and E. faecalis in as little as 5 seconds.34 UV light can even be used to disinfect water without the addition of other harsh chemicals.35

The Importance of Vitamin D for Health, Disease Prevention and Longevity

The list of conditions that benefit from vitamin D and/or UV light exposure is long enough to fill several books, but here are a few more examples from the scientific literature. I also recommend reading through "Sunlight: For Better or For Worse? A Review of Positive and Negative Effects of Sun Exposure,"36 published in the journal Cancer Research Frontiers earlier this month.

Multiple sclerosis (MS)

A pilot study by Johns Hopkins researchers suggests vitamin D3 supplementation is a safe way to regulate hyperactive immune responses.

MS patients with higher levels of vitamin D tend to experience less disabling symptoms.37


Hypomethylation — an epigenetic abnormality found in tumors,38 cardiovascular disease and impaired immune function — is more prevalent among those with low vitamin D levels.

In one study, a once-monthly dose of 18,000 IU, 60,000 IU, or 120,000 IU's of vitamin D was administered to vitamin D deficient African American teens with low methylation levels.

The higher the vitamin D dose, the higher the subsequent methylation activity.39,40

Eye health

Australian researchers have found that kids who spend most of their days indoors have significantly higher rates of high degree myopia (short-sightedness).

As reported by The Daily Mail:41 "The researchers believe that the neurotransmitter dopamine is responsible. It is known to inhibit the excessive eyeball growth that causes myopia. Sunshine causes the retina to release more dopamine."

Uveitis, eye inflammation that affects the middle layer in your eye wall, is also more prevalent among those who have low vitamin D levels.42

Among patients with uveitis, mean vitamin D levels were just over 26 ng/ml. Patients without this condition had a mean level of nearly 36 ng/ml.

Overall, the odds of developing uveitis declined by 6 percent for each one unit increase in vitamin D.


Recent research suggests psoriasis shares genetic factors with metabolic syndrome and obesity. Psoriasis is nearly twice as prevalent among diabetics as non-diabetics.

People with these conditions all tend to have systemic inflammation and higher levels of certain inflammatory markers, including tumor necrosis factor. They also tend to have lower vitamin D levels.

Although psoriasis appears as a skin condition, it is actually an autoimmune disease. Part of the reaction occurs when a type of white blood cell called a T cell mistakenly attacks healthy skin cells.

If you have psoriasis, it is imperative that you have your vitamin D levels tested and maintain levels in the therapeutic range of 40 to 60 ng/ml year-round.

Vitamin D is a potent immune modulator, making it very important for the prevention of autoimmune diseases.

Mood and mental health

Sun exposure boosts the feel-good brain chemical serotonin, which is in part why you feel better after spending some time in the sun.

Light therapy has long been the go-to treatment for seasonal affective disorder, and more recent research suggests it can be useful in the treatment of major depression as well.43 

Schizophrenia has also been linked to maternal lack of sun exposure during pregnancy.44

Sexual health

Sunlight helps boost men's libido, by affecting testosterone. Australian research reveals that men's' testosterone levels rise and fall with the seasons, peaking during August, and hitting their lowest levels in March.

Researchers at Johns Hopkins have also linked low vitamin D levels with an increased risk for erectile dysfunction (ED).45

Recent research also warns that use of sunscreen may harm male fertility, courtesy of the endocrine disrupting chemicals found in them.

Scientists tested 29 of 31 chemicals approved for use as UV filters in sunscreens in the U.S. and European Union, and found that 45 percent of them inhibited sperm activity by mimicking the female hormone progesterone.

These findings held even when the chemicals were used at very low levels.46,47 If you need to use sunscreen, opt for a zinc-based version, or use clothing.

All-cause mortality

One 20-year long study48,49 concluded 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."

Women who avoided sun exposure had double the all-cause mortality rate of those who got regular sun exposure.

Another 54-month long study50 published in 2013, involving more than 422,800 healthy adults, found that those who were most deficient in vitamin D had an 88 percent increased mortality risk.

Benefits outweigh melanoma risk

A study published in Public Health Nutrition 2012 concluded that: "The overall health benefit of an improved vitamin D status may be more important than the possibly increased cutaneous malignant melanoma risk resulting from carefully increasing UV exposure."51

While many fear the risk of melanoma, it may be worth pondering the actual magnitude of that risk.

As noted by the Association of Health Care Journalists (AHCJ),52 an oft-repeated quote is that "use of sunbeds before the age of 35 is associated with a 75 percent increase in the risk of melanoma."  

That 75 percent figure is based on an analysis of several studies, the strongest of which found that "less than three-tenths of 1 percent who tanned frequently developed melanoma while less than two-tenths of 1 percent who didn't tan developed melanoma."

That's amounts to a 55 percent increase, but when pooled with other studies, the average increase came to 75 percent. While this sounds ominous, remember that we're still talking about a risk that is well below one percent.

Instead of having a 0.2 percent risk for melanoma, your risk rises closer to 0.35 percent with frequent sun exposure.

So when contemplating the risks of sun exposure to optimize your vitamin D, compare and balance that 0.35 percent risk for melanoma with a 67 percent decreased risk of cancer, and an 88 percent decreased risk of dying from any cause.

How to Reduce Your Risk of Skin Cancer While Benefitting From Sensible Sun Exposure

An important risk factor for melanoma is overexposure to UV radiation either from direct sunlight or tanning beds/lamps. Frying yourself for several hours on the weekend here and there is not a wise choice. You want to take precautions to avoid sunburn at all cost. If you're going to the beach, bring long-sleeved cover-ups and a wide-brimmed hat, and cover up as soon as your skin starts to turn pink.

Realize that unless you have very dark skin you don't need to spend hours in the sun. For lighter-skinned people, optimizing your vitamin D may require mere minutes in the sun with minimal clothing.  To minimize risk while maximizing benefits of UV exposure, here are a few factors to consider. If you pay close attention to these, you can determine, within reason, safe exposure durations.

  • You should know your skin type based on the Fitzpatrick skin type classification system, which has been around for decades. The lighter your skin, the less exposure to UV light is necessary. The downside is that lighter skin is also the most vulnerable to damage from overexposure.
  • For very fair skinned individuals and those with photodermatitis, any sun exposure may be unwanted and they should carefully measure vitamin D levels while ensuring they have an adequate intake of vitamin D, vitamin K2, magnesium, and calcium.
  • For most individuals, safe UV exposure is possible by knowing your skin type and the current strength of the sun's rays. There are several apps and devices to help you optimize the benefits of sun exposure while mitigating the risks. . Also be extremely careful if you have not been in the sun for some time. Your first exposures of the year are the most sensitive, so be especially careful to limit your initial time in the sun.

+ Sources and References

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