It’s sunlight that gives us warmth – and who doesn’t feel cheerier and more energetic on a bright, sunny day? Yet not everything about sun exposure is “sunny.” Beyond making you feel good and offering certain health benefits, it can also pose risks. Let’s dig deeper and explore the relationship between sun, wellbeing, and health.
The Sunny Side of Sunlight
One well-known health benefit of sun exposure is the effect it has on vitamin D, an essential vitamin your body needs to thrive. So close is the relationship between sun and vitamin D production that people sometimes refer to vitamin D as “the sunshine vitamin.”
When you step out into the sunlight with bare skin, the sun’s ultraviolet rays hit the surface of your skin. There, it encounters 7-dehydrocholesterol, a precursor to vitamin D. Sunlight supplies the energy to activate 7-dehydrocholesterol and starts it down the path to forming one of the active forms of vitamin D called vitamin D3. The kidneys and liver make this possible too.
Why is vitamin D so essential? It helps your body absorb and retain the calcium you need for bone health. Yet it also plays a role in balancing your immune system, the interplay between immune surveillance, which protects you against infection, and inflammation, an overreaction of the immune system that’s harmful. In fact, research links exposure to sunlight and a higher vitamin D level to a lower risk of some developing autoimmune conditions, like multiple sclerosis.
Unless you take vitamin D supplements, sun exposure is the way you’ll get most of your vitamin D, as there are limited food sources of vitamin D. Eggs, salmon, mushrooms exposed to sunlight, and fortified foods contain modest quantities. Of these, fortified foods are the best dietary source for most people. So, sunlight makes it possible to meet your body’s vitamin D requirements, assuming you get enough of it.
Can Sunlight Lower Your Risk of Cardiovascular Disease?
Another benefit of sun exposure is the effect it has on your blood vessels. Studies link sun exposure to lower blood pressure, and it’s not just the fact that the sun relaxes you. When sun hits your skin, it causes your arteries to produce more nitric oxide, a natural chemical that widens that and lowers your blood pressure. As you know, high blood pressure is a risk factor for cardiovascular disease.
The Well-Being Benefits of Sunlight
Your natural rhythm, known as circadian rhythms, controls important aspects of your health, including hormone release, metabolic health, and even your mood. Exposure to natural light, particularly sunlight, in the morning helps set your biological clock and circadian rhythms in a manner that promotes good metabolic health and mood.
Natural sunlight can help your mood and even help you sleep better at night. It’s not uncommon for people to experience Seasonal Affective Disorder (SAD), a type of depression that responds to light therapy, in the winter months when the days are shorter, and they get less sun and natural light exposure. Sunlight helps you produce brain biochemicals, called neurotransmitters, like serotonin, which elevate your mood.
The Dark Side: Risks of Excessive Sun Exposure
As with most things, it’s not all roses when it comes to sun exposure. Ultraviolet rays from the sun come in two main types, ultraviolet A (UVA) rays and ultraviolet B (UVB) rays. UVB rays cause sunburn, which damages your skin and increases the risk of skin cancers, including the most serious type, melanoma. But don’t think that UVA rays are kind to your skin. Although they don’t cause sunburn, they penetrate deeper than UVB rays and cause other problems, like deeper skin damage and premature skin aging.
Despite its benefits, unprotected sun exposure comes with risks. The primary concern is skin damage caused by ultraviolet (UV) radiation. UVA rays penetrate deeply into the skin, generating DNA-damaging free radicals and accelerating skin aging. UVB rays, on the other hand, are responsible for sunburn and direct DNA damage.
According to the World Health Organization (WHO) getting too much exposure to ultraviolet light accounts for 0.1% of the total global burden of disease in disability-adjusted life years. While this might seem small, the long-term nature of UV damage means that the effects often manifest later in life.
And there’s another major risk of too much sun exposure and it involves your eyes. When you expose your eyes to ultraviolet light with no filtering, it causes oxidative damage to the lenses of your eyes. Such free radical damage increases the risk of cataracts. Plus, it penetrates to the back of your eyes and damages the light-sensitive structure known as your retina. (one in each eye). Over time, this predisposes to age-related macular degeneration (AMR), a common cause of visual loss after the age of fifty.
Some studies also show that too much sun exposure suppresses your immune system and predisposes to certain types of viruses, like herpes simplex one that causes cold sores.
Strike a Balance: Safe Sun Exposure
Ideally, you want to enjoy the benefits of sunlight and sun exposure while minimizing the risks. This means striking a healthy balance. How much sun you need for adequate vitamin D production will vary with the time of day, time of year, latitude in which you live, and your skin type.
Most people need between 10 and 30 minutes of sun exposure several times per week (on bare skin) to produce adequate vitamin D. Getting that amount of sunlight, for most people, isn’t enough to increase their risk of skin cancer. However, if you have a strong family history of skin cancer or have very pale skin or red hair, you may be better served by taking a vitamin D supplement and limiting sun exposure.
Also, if you live in Northern latitudes, it’s unlikely you can meet your body’s vitamin D needs in the winter through sunlight exposure alone in the winter due to the weakness of the sun’s rays.
As far as damage to your eyes, you can wear UVA and UVB blocking sunglasses to protect your eyes. Experts recommend short periods of unprotected sun exposure, followed using protective measures. The American Academy of Dermatology suggests the following guidelines:
- Apply a broad-spectrum, water-resistant sunscreen with SPF 30 or greater.
- Wear protective clothing, including a wide-brimmed hat and UV filtering sunglasses.
- Seek shade, especially between 10 a.m. and 4 p.m. when UV rays are strongest.
- Be cautious near reflective surfaces like water, snow, and sand.
- Avoid tanning beds, which emit harmful UV radiation.
Be aware that wearing sunscreen reduces vitamin D production, although most people don’t put on a thick enough layer to block it entirely. However, the protection sunscreen offers against sun damage may outweigh the downsides of wearing it. Always talk to your healthcare provider about risk factors and how much sun exposure is safe for your skin.
Conclusion
The relationship between humans and sunlight is indeed bittersweet. While you need sun exposure to make vitamin D, balance and knowing how much sun exposure is safe for you matters. You always have the option of taking a vitamin D supplement. Even if you avoid sun exposure due to pale skin or a history of skin cancer, you should still expose your eyes to natural light in the morning to set your internal biological clock. You can do this by stepping outside early when the sun’s rays are at their weakest and least damaging.
References:
- Mead MN. Benefits of sunlight: a bright spot for human health. Environ Health Perspect. 2008 Apr;116(4): A160-7. doi: 10.1289/ehp.116-a160. Erratum in: Environ Health Perspect. 2008 May;116(5):A197. PMID: 18414615; PMCID: PMC2290997.
- Wacker M, Holick MF. Sunlight and Vitamin D: A global perspective for health. Dermatoendocrinol. 2013 Jan 1;5(1):51-108. doi: 10.4161/derm.24494. PMID: 24494042; PMCID: PMC3897598.
- org. “Sun Safety,” August 8, 2021. https://www.hopkinsmedicine.org/health/wellness-and-prevention/sun-safety.
- Holick MF. Sunlight, ultraviolet radiation, vitamin D and skin cancer: how much sunlight do we need? Adv Exp Med Biol. 2014;810:1-16.
- Baggerly CA, et al. Sunlight and Vitamin D: Necessary for Public Health. J Am Coll Nutr. 2015;34(4):359-365.
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