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14 Health Benefits of Sunlight + Dangers & Safety Tips

Written by Aleksa Ristic, MS (Pharmacy) | Last updated:
Puya Yazdi
Medically reviewed by
Puya Yazdi, MD | Written by Aleksa Ristic, MS (Pharmacy) | Last updated:

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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 [1].

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 [1].

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 [1].

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 [1].

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 [2].

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 [3].

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 [4].

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 [5].

Vitamin D is synthesized in the skin through a photosynthetic reaction triggered by exposure to UVB radiation [6].

Most cases of vitamin D deficiency are due to lack of outdoor sun exposure [6].

At least 1,000 different genes, governing virtually every tissue in the body, are regulated by the active form of vitamin D [5].

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 [5].

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 [5].

Sunbathing has been recommended for centuries as an effective treatment for rickets [7].

Low vitamin D levels cause and worsen osteoporosis and osteomalacia (painful bone disease) in both men and women [6].

As if this weren’t compelling enough, a recent study showed that low vitamin D levels from sun avoidance increase all-cause mortality [8].

1.1) Ideal Vitamin D levels

  • At risk of Vitamin D deficiency: Serum 25OHD less than 30 nmol/L (12 ng/mL) [9].
  • At risk of Vitamin D inadequacy: Serum 25OHD 30-49 nmol/L (12-19 ng/mL) [9].
  • Sufficient in Vitamin D: Serum 25OHD 50-125 nmol/L (20-50 ng/mL) [9].
  • Possibly too Much Vitamin D: Serum 25OHD greater than 125 nmol/L (50 ng/mL) [9].

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].

The SCN receives its messages from the eye. These messages will depend on how much light the eye is being exposed to [12, 13].

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 [14].

Getting enough sunlight during the daytime is essential for good sleep. Getting enough light increases night-time melatonin levels [15]. You might also find you go to bed earlier [16].

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 [17].

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 [5].

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 [5].

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 [18].

Ironically, high sun exposure increases survival rates in patients with early-stage melanoma [19].

A large number of public health messages have focused on the dangers of too much sun exposure, such as skin cancer. On the other hand, today’s science tells us that sensible sun exposure is essential for physical and mental health. Read on to learn the amazing benefits of sunlight, potential dangers, and safety tips.

What is Sun Exposure?

Planet Earth has been bathing in sunlight for more than 3 billion years [1].

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 [1].

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 [1].

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.

Vitamin D

Whenever a study shows an association with low vitamin D, it means that people’s health is suffering due to insufficient sun exposure.

Circulating vitamin D levels provide a surrogate measure of sun exposure. Often times, other molecules and pathways induced by sun exposure, rather than just vitamin D-driven processes, explain many of the benefits often attributed to vitamin D [2].

Therefore, vitamin D supplements can not be considered a substitute for moderate sun exposure.

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 [5].

Vitamin D is synthesized in the skin through a photosynthetic reaction triggered by exposure to UVB radiation [6].

Most cases of vitamin D deficiency are due to a lack of outdoor sun exposure [6].

At least 1,000 different genes governing virtually every tissue in the body are regulated by the active form of vitamin D [5].

1.1) Vitamin D Blood Levels and Nutritional Status [9]

  • 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

Our “internal clock” in the hypothalamus receives messages from the eye. These messages will depend on how much light the eye is being exposed to [12, 13].

So, the body’s key way of telling the time of day will depend on how much light the eyes receive at certain times of the day.

This is essential for 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 [14].

Getting enough sunlight during the daytime is essential for good sleep. Getting enough light increases night-time melatonin levels and helps you go to sleep on time [15, 16].

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 [17].

3) Strengthens the Bones

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 moderate sun exposure is vital for healthy bones [5].

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 [5].

Sunbathing has been recommended for centuries as an effective treatment for rickets [7].

Vitamin D deficiency causes and worsens osteoporosis and osteomalacia in both men and women [6].

Increasing sunlight exposure and blood Vitamin D levels decreases knee cartilage loss in those with arthritis [20].

4) Improves Mood and Mental Health

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 [21, 22, 23].

Sun and Dopamine

Light also increases dopamine release and dopamine DRD2 receptors [24, 25, 23].

Seasonal Affective Disorder (SAD) is a result of impaired mental health due to the lack of sun exposure. Symptoms include lethargy, worsened reflexes, weight gain and low motivation, which all suggest a less functional dopamine system [23].

Acute bright light exposure (7,000 lux for 10 min) increased blood flow in dopamine-rich areas of the brain (striatum) in healthy volunteers [23].

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 compared with healthy controls [23].

Sun and Vitamin D

In older individuals, low vitamin D levels are associated with low mood [26].

Actually, a 2008 study concluded that people with clinical depression have vitamin D levels 14% lower than normal [27].

One study found that vitamin D levels correspond to the mood of women with diabetes [28].

An interesting study found that bipolar patients recovered faster if they had a window facing east to the morning sun [29].

In Australia, rates of suicide amongst middle-aged people increase in winter when sunlight is minimal [30].

The impact of sunlight on mood might have something to do with the dense number of vitamin D receptors in the hypothalamus [31].

Sunlight also increases relaxation and contentment by increasing beta-endorphins – the same chemicals responsible for “runner’s high” [32].

5) Supports Longevity

In a Swedish study of over 29,500 women, there was a twofold increase in mortality among those who avoided sun exposure, compared with the highest sun exposure group [3].

Nonsmokers who avoided sun exposure had a life expectancy similar to smokers in the highest sun exposure group, indicating that avoidance of sun exposure may be as detrimental as smoking. Compared to the highest sun exposure group, life expectancy of avoiders of sun exposure was 0.6-2.1 years lower [3].

6) Cancer Protection

Although skin cancer has been associated with too much UV exposure, especially in areas of the world with a damaged ozone layer, not getting enough sun is associated with a number of other cancers [5].

For example, those who live in places with less sun (e.g high latitudes) have a higher chance of dying from breast, ovarian, colon, pancreatic, prostate, and other cancers [5].

According to a study of 1179 women, taking 2-4 times the daily recommended intake of vitamin D3 (200-600 IU) and calcium is associated with two times lower cancer rates [18].

Importantly, this doesn’t mean that getting enough sun and having optimal vitamin D levels alone will prevent or treat any form of cancer.

7) Supports Heart Health

Vitamin D deficiency links to cardiovascular disease can be found in a number of studies demonstrating a 30-50% higher cardiovascular morbidity and mortality associated with reduced sun exposure [33].

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 [33].

According to some researchers, rates of high blood pressure also correlate with latitude (i.e. less near the equator) and generally rise during winter [34].

The blood pressure-lowering effect of sunlight might be due to its ability to increase nitric oxide in the body [34, 35].

Active D/Calcitriol plays versatile roles in heart health and fluid balance [33].

There are many mechanisms by which low calcitriol and high PTH harm your heart.

8) Improves Brain Function

One study found that chronic sun deprivation leads to cognitive impairment [36].

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 [37].

In elderly women, vitamin D deficiency leads to cognitive impairment [38].

Certain wavelengths found in natural sunlight affect the activity of brain structures involved in alertness [37].

Researchers have suggested 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 [39].

9) Protects Against Brain Disorders

Schizophrenia

Low vitamin D levels correlate with schizophrenia and depression [40].

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 [41].

Alzheimer’s

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 [42].

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 [43].

People with Alzheimer’s have disturbed circadian rhythms, and the sun is critical to circadian rhythms [44].

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 [45].

Increased light exposure consolidates sleep and strengthens circadian rhythms in severe Alzheimer’s disease patients [46].

Parkinson’s Disease

In some patients with Parkinson’s disease, 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% [23].

10) Improves Dental Health

Sun exposure and subsequent increases in vitamin D levels may reduce the formation of dental cavities [47, 48].

Furthermore, studies have determined that people who live in sunny locations have fewer cavities, and vice versa [49, 50].

Some children with severe early childhood cavities are more likely to have vitamin D deficiency [51].

Vitamin D concentrations at or above 30-40 ng/ml may significantly lower the formation of dental caries [52].

Another study found that 800 IU/day of vitamin D was enough to prevent cavities in children [53].

11) Helps Prevent Diabetes

Vitamin D deficiency has been associated with insulin resistance, type 1 and 2 diabetes, and metabolic syndrome [33, 54].

Individuals with autoimmune type-1 diabetes have low levels of vitamin D, too [55].

Vitamin D receptors are present in the pancreas, increasing insulin secretion and sensitivity [33].

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 [56].

12) 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 [57].

The effects are partly mediated by dopamine and orexin.

13) Natural Painkiller

One study found that post-surgery exposure to sunlight decreased stress and pain, thus minimizing the need for painkillers by 21% [58].

The painkilling effects of sunlight are probably due to its ability to increase beta-endorphins in the skin. Beta-endorphins are our internal painkillers [59].

In one study, 88% of people with chronic pain had vitamin D deficiency [60].

14) Balances the Immune System

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) [61].

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 [62].

A study on 10,000 nurses revealed the same pattern for rheumatoid arthritis [63].

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 [64].

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 [65, 66].

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 [67, 68].

Vitamin D and Beyond

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 [69].

Vitamin D is a crucial immunomodulatory factor; it strengthens the immune system but also prevents over-activation that leads to autoimmunity [70].

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 [71, 72].

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, 73].

The UVB light boosts regulatory T cells (Tregs), which prevent excessive inflammation and autoimmune response [74].

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.

If these genes are not working well, you will need more sun:

Sunbathing Tips

What determines “optimal” sun exposure? The amount of sun that is optimal or excessive will depend on [5]:

  • Skin type
  • Health status
  • Latitude
  • Time of the day

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 [5].

A good general approach would be to start off with 10 minutes of sun exposure per day and slowly build up, making sure to avoid getting sunburned.

Exposing a bigger surface of your skin and sunbathing around midday will help you make more vitamin D without spending too much time in the sun.

If you have to spend more time outside, make sure to protect the skin by:

  • Covering up with clothes
  • Looking for a shade
  • Using sunscreen

If you’re worried about the potentially toxic chemicals in commercial sunscreen products, look for the ones with non-nano zinc oxide instead [75, 76].

Keep in mind that the above measures will hinder your vitamin D absorption, too, so use them only if at risk of excessive sun exposure and sunburns.

Dangers of Excessive Sun Exposure

Just like anything else, too much sun may also harm your health. Excessive exposure increases the risk of:

  • Sunburns and skin damage [77, 78]
  • Skin aging [79]
  • Sunstroke (heat stroke) [80]
  • Eye damage [81]
  • Skin cancer [82]

Why Some People May Get Skin Cancer From Sun Exposure

Some of the main reasons for negative, skin-damaging effects of UV light from sun exposure include [83, 84, 85, 86]:

  • Getting too much sun in one shot
  • Not building exposure gradually
  • Circadian rhythm dysfunction
  • Diets low in antioxidants and healthy fats
  • Excessive showering (taking off protective oils)
  • Not spreading out the sun (gets concentrated in specific places)
  • Dehydration

About the Author

Aleksa Ristic

Aleksa Ristic

MS (Pharmacy)
Aleksa received his MS in Pharmacy from the University of Belgrade, his master thesis focusing on protein sources in plant-based diets. 
Aleksa is passionate about herbal pharmacy, nutrition, and functional medicine. He found a way to merge his two biggest passions—writing and health—and use them for noble purposes. His mission is to bridge the gap between science and everyday life, helping readers improve their health and feel better.

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