Health Benefits of Sunlight Exposure

Most public health messages of the past century have focused on the hazards of too much sun exposure. Long wave ultraviolet radiation (95–97% of the UVR that reaches Earth’s surface) penetrates deeply into the skin, where it can contribute to skin cancer indirectly via generation of DNA-damaging molecules such as hydroxyl and oxygen radicals. Sunburn is caused by too much UVB radiation; this form also leads to direct DNA damage and promotes various skin cancers. Both forms can damage collagen fibers, destroy vitamin A in skin, accelerate aging of the skin, and increase the risk of skin cancers. Excessive sun exposure can also cause cataracts and diseases aggravated by UVR-induced immunosuppression such as reactivation of some latent viruses.

Positive Effects of the Sun

Vitamin D production

The best-known benefit of sunlight is its ability to boost the body’s vitamin D supply; most cases of vitamin D deficiency are due to lack of outdoor sun exposure. At least 1,000 different genes governing virtually every tissue in the body are now thought to be regulated by 1,25-dihydroxyvitamin D₃ (1,25[OH]D), the active form of the vitamin, including several involved in calcium metabolism and neuromuscular and immune system functioning.

Although most of the health-promoting benefits of sun exposure are thought to occur through vitamin D photosynthesis, there may be other health benefits that have gone largely overlooked in the debate over how much sun is needed for good health [see “Other Sun-Dependent Pathways,” p. A165]. As for what constitutes “excessive” UVR exposure, there is no one-size-fits-all answer, says Lucas: “‘Excessive’ really means inappropriately high for your skin type under a particular level of ambient UVR.”

Enhances Your Mood

Dr. Carey Bligard, MD, UnityPoint Health says there are many benefits from sunlight, including that it is a free mood enhancer. Being in the sun can make people feel better and have more energy. Sunlight increases the levels of serotonin in the brain, which is associated with improved mood. Not surprisingly, serotonin levels are highest in the summer.

Treats Seasonal Depression (commonly referred to as Seasonal Affective Disorder)

In certain people, the lack of sunlight in the winter seems to trigger depression. Symptoms include bad moods, difficulty making and keeping friends, overeating, tiredness and sleeping too much. Seasonal depression, formerly known as Seasonal Affective Disorder, is rare in the warmer months.

Relieves Stress

Everyone experiences stress for various factors, such as family, work and health issues. Dr. Bligard says stress can be relieved in a variety of ways, including exercise, having relaxing hobbies, walking the dog or by getting out in the fresh air for a little sun exposure.

Improves Sleep

Sunlight exposure impacts how much melatonin your brain produces, which is what tells your brain when it is time to sleep. When it gets dark, you start producing melatonin so you are ready to sleep in about two hours. With more sunlight in the summer, you are likely to feel more awake. Dr. Bligard points out that modern technology has allowed us to change our light exposure artificially with lights, TV screens and computer screens (including tablets and cell phones). Consequently, the incidence of insomnia is much higher now than it was before these devices were invented.

Protection from the Sun

Much of the damage to our skin caused by sun exposure can be prevented. Sunscreen must be applied 20 minutes before going out in the sun and should be reapplied after two hours in the sun and after swimming or heavy sweating. You can also protect yourself with UV filtering sunglasses, long sleeves or a brimmed hat. If you are going to be outside for long periods, sit under a cover of a building, an umbrella or a tree that has dense shade underneath.