A large number of public health messages over the past century have focused on the dangers of too much sun exposure, such as aging, skin cancer and DNA damage. However, in reality, today’s science tells us that exposure to ultraviolet radiation (UVR) in sunlight has many beneficial effects on human health.
What is Sun Exposure?
Planet Earth has been bathing in sunlight for more than 3 billion years .
As life forms evolved in the ocean they were exposed to sunlight. Eventually, early life learned to make carbohydrates using sunlight as their energy source .
Given the importance of sunlight for life on this planet, it makes sense that all lifeforms, including humans, have evolved to use the power of the sun to their advantage .
Humans have a long history of using sunlight therapy that dates back to the ancient Greeks. Today, sunlight therapy is referred to as heliotherapy.
We instinctively think people with a tan look healthier. A tan is simply the body’s way of protecting itself from the power of the sun’s rays .
Hopefully, after reading the following benefits of sun exposure, you will start to appreciate the powerful effect that the sun can have on your health.
It’s important to note, that whenever a study shows an association with low vitamin D, all we really know from that is that people aren’t getting enough sun. Vitamin D is a good measure of sun exposure on your body.
Circulating vitamin D levels provide a surrogate measure of sun exposure and that it is the other molecules and pathways induced by sun exposure, rather than vitamin D-driven processes, that explain many of the benefits often attributed to vitamin D .
Therefore, if you take vitamin D, you won’t prevent many of the risks associated with lower vitamin D. The safest way to prevent these risks is to actually get sun.
Mechanisms by Which Sun Benefits Health
Sun increases or provides:
- Contains Infrared, which has a myriad of benefits
- Contains Full Spectrum Light, which increases dopamine and serotonin and certain spectrums can improve mitochondrial function (red light)
- Increases MSH and MC4R receptors
- Increases Beta-endorphins, which improves mood
- Relaxes the nervous system and makes us calmer
- Increases Nitric Oxide, which helps improve blood flow
- Increases Vitamin D
- Increases Heat shock proteins
- Lowers inflammation (UV is an immunosuppressant)
- Improves Blood flow – blood flows where UV shines
- Increases metabolism
- Is anti-Microbial – the sun can irradiate large amounts of blood – against fungi, bacteria viruses, etc…
- Increases CD8 Cells, which help the immune system
- Increases sulfhydryl groups (necessary for glutathione)
- Breaks down adrenaline, estrogen, cortisol, prolactin, progesterone (and testosterone)
Why People May Get Skin Cancer From Sun
- We get too much sun in one shot
- We don’t build up exposure gradually (we take a vacation)
- Circadian rhythm dysfunction (circadian processes protect us from the sun)
- We have lower NAD+ (which is our natural sunscreen)
- We have a bad diet
- We shower and take off protective oils
- We don’t spread out the sun (gets concentrated in specific places),
- We don’t consume enough DHA
- We don’t drink enough water
Sun Exposure Decreases Risk of Dying
In southern Sweden, there was a 2X increased risk of death among those who avoided sun exposure compared with the highest sun exposure group .
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 as significant as smoking. Compared to the highest sun exposure group, life expectancy of avoiders of sun exposure was reduced by 0.6-2.1 years .
Top Health Benefits of Sun Exposure
1) Increases Vitamin D Levels
The best-known benefit of sunlight is its ability to boost the body’s vitamin D supply .
Vitamin D is synthesized in the skin through a photosynthetic reaction triggered by exposure to UVB radiation .
Most cases of vitamin D deficiency are due to lack of outdoor sun exposure .
Vitamin D accumulates in cells of the intestines, where it enhances calcium and phosphorus absorption, controlling the flow of calcium into and out of bones. Thus, adequate vitamin D production through sun exposure is vital for healthy bones .
Without enough vitamin D, bones will not form properly. In children, this deficiency is called rickets, a disease that retards growth and causes skeletal deformities, such as bowed legs .
Sunbathing has been recommended for centuries as an effective treatment for rickets .
Low vitamin D levels cause and worsen osteoporosis and osteomalacia (painful bone disease) in both men and women .
As if this weren’t compelling enough, a recent study showed that low vitamin D levels from sun avoidance increase all-cause mortality .
1.1) Ideal Vitamin D levels
- At risk of Vitamin D deficiency: Serum 25OHD less than 30 nmol/L (12 ng/mL) .
- At risk of Vitamin D inadequacy: Serum 25OHD 30-49 nmol/L (12-19 ng/mL) .
- Sufficient in Vitamin D: Serum 25OHD 50-125 nmol/L (20-50 ng/mL) .
- Possibly too Much Vitamin D: Serum 25OHD greater than 125 nmol/L (50 ng/mL) .
2) Sets Circadian Rhythm (Important!)
Studies published in the ’70s showed that part of the brain (the hypothalamus), the suprachiasmatic nucleus (SCN), functions as the core circadian pacemaker in mammals. Basically, the SCN helps your body tell the time of day [10, 11].
So, your body’s key way of telling the time of day will depend on how much light your eyes receive at certain times of the day.
This is very important for your health. Studies show that having a good circadian rhythm is important for the regulation of sleep-wake cycles, hormone release, body temperature and other important bodily functions .
Humans are most sensitive to light stimuli during the night. As a result, just as important for entraining your circadian rhythm as getting sunlight in the morning is avoiding artificial light at night .
This is why I use blue blocking glasses after sunset. These Swanick glasses are better for social settings.
3) May Protect Against Cancer
Although skin cancer has been associated with too much UVR exposure, especially in areas of the world with a damaged ozone layer, a number of other cancers could result from too little sun .
For example, those who live in places with less sun (e.g high latitudes) are at higher risk of dying from breast, ovarian, colon, pancreatic, prostate, and other cancers .
One study investigated the impact that vitamin D supplementation has on cancer rates. Results showered that taking 2-4 times the daily recommended intake of vitamin D3 (200-600 IU) and calcium resulted in a 50-77% reduction in expected cancer rates .
Ironically, high sun exposure increases survival rates in patients with early-stage melanoma .
Similarly, occupational exposure to sunlight lowers risk of skin cancers .
Most skin cancers occur on parts of the body that are covered by clothes .
4) Can Protect Against Heart Disease and Lower Blood Pressure
Vitamin D deficiency links to cardiovascular disease can be found in a number of studies demonstrating a 30% to 50% higher cardiovascular morbidity and mortality associated with reduced sun exposure caused by changes in season or latitude .
Conversely, the lowest rates of heart disease are found in the sun-drenched Mediterranean coast and in southern versus northern European countries. Cardiac death has been reported to be the highest during the winter months .
A number of studies have attempted to correlate vitamin D3 with cardiovascular events. Heart attack patients had lower mean D3 concentrations than control subjects. There was a 57% reduced risk for those above compared with those below the median of D3 .
Rates of high blood pressure correlate with latitude (i.e. less near the equator) and generally rise in winter .
One study exposed a group of high blood pressured adults to a full spectrum tanning bed. After three months, participants had an average 180% increase in their Vitamin D levels. They also had an average 6 mm Hg decrease in their systolic and diastolic blood pressures .
Active D/Calcitriol normalizes the impaired heart contractility observed in experimental vitamin D deficiency .
Calcitriol regulates heart muscle production and prevents thrombus formation and cell adhesion .
Calcitriol is known to suppress the synthesis and secretion of atrial natriuretic peptide and increases matrix Gla protein, a protein that protects against arterial calcification .
Having lower vitamin D increases PTH, which has many detrimental effects on the heart .
There are many mechanisms by which low calcitriol and high PTH harm your heart.
5) Makes You Happier and Combats Depression and SAD
The 3 main mechanisms by which sun benefits mood is by the serotonin and dopamine system and vitamin D.
Sun and Serotonin
One study found that sun exposure increases levels of serotonin and its associated receptors in the brains of healthy men. This is important as relatively high serotonin levels result in better moods and a calm, focused mental outlook [24, 25, 26].
Sun and Dopamine
In Seasonal Affective Disorder (SAD), symptoms include lethargy, worsened reflexes, weight gain and low motivation, which all suggest a less functional dopamine system. In these people, dopamine transporters are reduced in dopamine-rich areas (striatum) .
Acute bright light exposure (7,000 lux for 10 min) increased blood flow in dopamine-rich areas of the brain (striatum) in healthy volunteers .
In Parkinson’s, where dopamine neurons are damaged, light exposure (1,000-1,500 lux, 1 hour daily for 2 weeks) improved mood, social activity, and motor function and, in some cases, reduced medication for dopamine replacement by 13%-100% .
Consistent with this, the dopamine DRD2 and DRD3 receptors were greater in people who got more sunshine . Patients with symptomatic SAD also show evidence of altered DA system function, and, compared with healthy controls .
In patients with SAD, neurotransmitter/catecholamine depletion reversed the therapeutic efficacy of bright light, which shows that the effects are mediated by neurotransmitters .
Finally, rodents kept in constant darkness showed increased destruction of neuronal cells that release neurotransmitters — changes that were associated with behavioral alterations indicative of a depressed state .
Even when precursors to dopamine were depleted, mood and agreeableness still increased from bright light, which shows that it works on the receptors or transporters .
Sun and Vitamin D
In older individuals, low vitamin D levels are associated with low mood .
Actually, a 2008 study concluded that people with clinical depression have vitamin D levels 14% lower than normal .
One study found that vitamin D levels correspond to the mood of women with diabetes .
An interesting study found that bipolar patients recovered faster if they had a window facing east to the morning sun .
In Australia, rates of suicide amongst middle-aged people increase in winter when sunlight is minimal .
Sunlight also increases relaxation and contentment by increasing beta-endorphins – the same chemicals responsible for “runner’s high” .
6) Is a Nootropic and Improves Brain Function
One study found that sun deprivation leads to cognitive impairment .
In another study, even brief exposure to sunlight substantially increased participant’s alertness and thinking ability. Increased alertness was due to increased activity in part of the brain called the thalamus .
In elderly women, vitamin D deficiency leads to cognitive impairment .
Certain wavelengths found in natural sunlight affect the activity of brain structures involved in alertness e.g. by increasing activity in networks involved in ongoing nonvisual cognitive processes .
Many researchers have argued that it is no coincidence that large numbers of Vitamin D receptors are found in the areas of the brain involved in complex planning, processing, and the formation of new memories .
7) Protects Against Brain Disorders
Low vitamin D levels increase the risk of schizophrenia and depression .
2,000 IU or more of vitamin D per day, during the first year of a child’s life, can reduce the risk of developing schizophrenia in later life .
One study found that, of the 80 participants with Alzheimer’s disease, over half had low vitamin D levels, which suggests that they aren’t getting enough sun .
Subjects with Alzheimer’s were exposed to bright light significantly less than healthy controls (0.5 vs. 1.0 hr). Healthy elderly received about two-thirds the duration of bright light received by healthy younger subjects .
There is an association between decreased exposure to bright light and the declines in sleep quality which typically accompany normal and diseased aging .
People with Alzheimer’s had disturbed circadian rhythms  and the sun is critical to circadian rhythms.
Red to infrared light therapy (λ = 600-1070 nm), and in particular light in the near infrared (NIr) range, is capable of arresting neuronal death. This therapy is being explored for Alzheimer’s and Parkinson’s patients . Sun contains infrared.
Increased light exposure consolidates sleep and strengthens circadian rhythms in severe Alzheimer’s disease patients .
In Parkinson’s, light exposure (1,000-1,500 lux, 1 hour daily for 2 weeks) improved mood, social activity, motor function and, in some cases, reduced medication for dopamine replacement by 13%-100% .
8) Sunbathing Encourages Dental Health
Children with severe early childhood cavities are more likely to have vitamin D deficiency .
Vitamin D concentrations at or above 30-40 ng/ml should significantly lower the formation of dental caries .
Another study on children found that 800 IU/day of vitamin D was enough to prevent cavities in children .
In dogs, increasing vitamin D levels led to increased calcification of the teeth .
9) May Reduce Diabetes
Vitamin D deficiency has been associated with insulin resistance, type 1 and 2 diabetes, and metabolic syndrome .
One study showed that, in Hispanic whites and Mexican Americans, there is an inverse relationship between Vitamin D levels and diabetes . Getting sun might be even more important for people who have ancestry from hot countries.
One study found that UV exposure lowered weight gain, glucose intolerance, and insulin resistance, in male mice fed a high-fat diet. The same benefits were not seen with vitamin D supplementation. The benefit of sun exposure may be partly due to the production of nitric oxide, a natural gas, in the skin .
Low blood vitamin D levels from inadequate sun exposure may promote the development of type 1 diabetes. Indeed, individuals with autoimmune type-1 diabetes have low levels of Vitamin D .
Vitamin D receptors are present in the pancreas, increasing insulin secretion and sensitivity .
One study demonstrated a 60% improvement in insulin sensitivity resulting from vitamin D treatment, a treatment more potent than with either troglitazone or metformin .
10) Sun Increases Wakefulness
Studies demonstrate that daytime exposure to bright light causes a significant decrease in sleepiness early in the evening. These changes are not necessarily associated with Vitamin D levels .
The effects are partly mediated by dopamine and orexin.
11) Sunlight Increases Sex Hormones
Sunlight raises sex hormones. Farmers use this mechanism to increase the laying rate of their hens .
A human study found that five treatments of UV light were enough to double sex hormone levels .
Studies show that, over the course of a summer, testosterone increases by roughly 20% . This effect is amplified when the genitals are exposed to the sun.
12) Sunlight is a Natural Pain Killer
One study found that post-surgery exposure to sunlight decreases stress and pain. Thus minimizing the need for painkillers by 21% .
The painkilling effects of sunlight are probably due to its ability to increase beta-endorphins in the skin. Beta-endorphins are natural painkillers .
In one study, 88% of people with chronic pain had Vitamin D deficiency .
13) Sunlight is Good For Your Eyes
Studies have shown that children who get more exposure to natural sunlight have a lower risk of developing myopia – short-sightedness .
Similarly, another study demonstrated that exposure to natural outdoor light reduced defocus-induced short-sightedness in monkeys .
14) Sun Exposure Treats Arthritis
Increasing sunlight exposure and blood Vitamin D levels decreases knee cartilage loss in those with arthritis .
15) Sun Protects Against Autoimmunity
In Australia, the highest incidence of multiple sclerosis has been reported in Tasmania (further from the equator), three times higher than in Northern Queensland (closer to the equator) .
A large global meta-analysis of over 300 trials confirmed that MS incidence is higher in regions at a higher latitude and lower UVB exposure. The connection remained significant after adjusting for other factors, such as genetic predisposition .
A study on 10,000 nurses revealed the same pattern for rheumatoid arthritis .
The incidence of type 1 diabetes is also influenced by the degree of latitude and UVB light. As UVB exposure increases, the incidence drops and reachers zero in regions with year-round UVB irradiance .
Also, the clinical onset of type 1 diabetes is much less likely to occur during the summertime .
The risk of immune-mediated diseases such as multiple sclerosis, type 1 diabetes, rheumatoid arthritis, ulcerative colitis, and lupus is highest for people born in April and lowest in October. These findings point to a protective role of maternal UVB exposure and vitamin D status in the 2nd and 3rd trimester [73, 74].
The incidence of multiple sclerosis in Iran increased eight times in the past 20 years. The main reason appears to be vitamin D deficiency and the lack of sun exposure in women. Namely, the Iranian revolution re-introduced stricter Islamic traditions including covering up of the skin of females in the last few decades [75, 76].
More Than Vitamin D
The UV light can suppress the symptoms of multiple sclerosis, asthma, and allergies in mice—regardless of their vitamin D status. It regulates the immune system by both vitamin D-dependent and independent mechanisms .
Vitamin D is a crucial immunomodulatory factor; it strengthens the immune system but also prevents over-activation that leads to autoimmunity .
Observational studies have linked vitamin D deficiency and insufficiency with increased prevalence of autoimmune diseases such as IBD and type 1 diabetes. In animal models, the lack of this vitamin triggered or worsened IBD, rheumatoid arthritis, MS, and other autoimmune conditions [79, 80].
However, vitamin D supplementation in humans has shown mixed results for autoimmunity; this indicates more complex protection from sun exposure, including the immunosuppressive effects of UV light [2, 81].
The UVB light boosts regulatory T cells (Tregs), which prevent excessive inflammation and autoimmune response .
16) Sun Fights Acne
Blue light has been shown to inactivate P. acnes bacteria. Daily self-treatment using a blue light treatment for mild-to-moderate inflammatory acne reduced the number of acne lesions significantly .
Topical aminolevulinic acid, methyl aminolevulinic acid, or other photosensitizing agents, applied before the laser treatment, improve the outcome of the treatment by decreasing oil gland activity .
Infrared light at 1450nm wavelength successfully helps treat acne, possibly by heating the oil gland and reducing its production of oil .
Therefore, the sun can help acne.
When Sun Might Be More Important
While there are many genes that are regulated by the sun, two of them here might be particularly important.
SelfDecode is a powerful app to analyze your SNPs.
If these genes are not working well, you will need more sun:
What determines “optimal” sun exposure? The amount of sun that is optimal or excessive will depend on your skin type, health status and your latitude .
For example, in a half-hour of the summer sun, a pale-skinned person can produce 50,000 IU (1.25 mg) vitamin D. In a tanned person, this exposure creates 20,000-30,000 IU, and 8,000-10,000 IU in dark-skinned people 
I recommend that people start off with 10 minutes of sun exposure per day and slowly build up until they reach the point just before their skin turns pink. Eventually, I think building up to at least one hour of sunlight per day is great.
When you are in the sun, try to get as naked as socially acceptable. Your chest and back are your solar panels when it comes to sunbathing.
If for some reason you can’t get sun exposure you might consider taking a high-quality Vitamin D3 supplement. This cannot replace the sun and you should only use it temporarily.
If you are sensitive to the sun, you should avoid the midday summer sun .
I do not recommend using sun creams because most have toxic chemicals in them. Instead, it’s better to put on some clothes, or just get out of the sun.
If you have to stay sun-exposed, then you should use a non-nano zinc oxide cream with as few ingredients as possible. This one is not too bad.
There was a large relationship between higher sun exposure and a lower age of onset of Bipolar.
A large springtime increase in sunlight may have an important influence on the onset of bipolar disorder, especially in those with a family history of mood disorders .
For more science-backed tips and tricks on how to start living a happier and healthier lifestyle, check out my book SelfHacked Secrets. Here I’ve compiled all of my research and what I’ve learned from helping over 1,000 patients fix their chronic health issues.