Strange Ways The Sun Can Affect Your Health

The sun has been a source of wonder and fascination since the dawn of humanity. This huge spinning star is pivotal to the existence of life on Earth: It provides us with light, keeps us warm, and helps plants and animals survive and grow (via National Geographic). Civilizations have harnessed its solar energy for thousands of years. As a powerful and omnipresent force in our cosmic system, it's no surprise that the sun has been deified over the course of history, serving as a potent symbol of wisdom in many cultures, from Paganism to Indian mythology to Native American spirituality (via Britannica).

The belief in the sun's curative properties has spanned centuries. Hippocrates, the Greek physician known as the "father of medicine," recommended sunbathing for various ailments, and had his own solarium to treat his patients, while the Roman philosopher Pliny once wrote: "Sun is the best remedy" (via Canadian Family Physician). In the early 20th century, the discovery of vitamin D (often referred to as the "sunshine vitamin") and how ultraviolet light promotes its synthesis in the skin was a huge step toward modern science recognizing the sun's health-promoting powers (via BoneKEy Reports).

But like Apollo — the "god of the sun" in Greco-Roman mythology — this mysterious celestial body has the capacity to both heal and harm us, warn scientists (via Environmental Health Perspectives). Here are some strange (and perhaps not-so-strange) ways the sun can impact your health.

A sunny day can uplift your mood in more ways than one. Getting an ample supply of sunlight throughout the day can help you nod off better at night, indicates research, which is naturally a key factor in feeling and functioning well (via Anticancer Research). This is because your circadian rhythm — your body's internal clock — follows the sun's patterns, and sunlight sends signals to your brain about when it's time to go to wake or sleep. When the sun's blue light rays enter your eyes, it slows or halts the production of melatonin, which is a hormone that helps us sleep better. In this way, the sun promotes wakefulness during the day. Melatonin levels typically rise again in the evening as the sky darkens, preparing the body for sleep (Sleep Foundation). But when the body's circadian rhythm is disrupted, melatonin can peak earlier or later than usual, throwing your normal sleep pattern off-balance. This might explain why people often feel more tired and groggy during the darker seasons, yet we tend to sleep like a baby after a lazy day in the sun.

There's intriguing evidence that people with vitamin D deficiency struggle with sleep disorders: They sleep fewer hours, have poor quality sleep, and frequently feel drowsy (via Nutrients). Some doctors recommend vitamin D supplementation to help improve sleep quality, however, the authors of the 2018 meta-analysis point out that further research is needed to investigate whether supplementation is an adequate replacement for sufficiently sun-exposed skin. So, don't forget to pull those curtains open first thing in the morning and let the light in.

The sun has long been revered for its medicinal prowess (via Medical History). In the early 20th century, sunlight therapy, also known as heliotherapy, was used to treat a number of different conditions including tuberculosis, rickets, and wounds, while many hospitals and sanitariums were built with south-east-oriented windows to ensure that patients could get sufficient sun exposure.

The belief that sunlight can promote a strong immune system is backed up by science today, which has found that exposure can help protect against the flu (via National Bureau of Economic Research). More recently, a study found that the rates of COVID-19 infections and deaths were higher in countries where people had lower levels of vitamin D (via Aging Clinical and Experimental Research). One explanation for this is that vitamin D deficiency impairs the development of "macrophages," which are white blood cells that attack pathogens in the body, explain the study authors. It's also said that adequate levels of vitamin D can improve the expression of infection-fighting genes that strengthen immunity and help kill off bacteria (via Scientific Reports). Some researchers point out, however, that it's not just sunlight exposure, but also an individual's diet, behavior, and skin color that influence their vitamin D status (via European Journal of Endocrinology).

Interestingly, a 2016 study suggests that the sun's blue light rays can boost your immune system without the involvement of vitamin D. Specifically, sunlight may trigger the synthesis of hydrogen peroxide, which energizes and improves the motility of T-cells, making them respond faster to bacterial infections.

At a blistering 27 million degrees Fahrenheit (hotter than any lava from the Earth's volcanoes), the sun's flames help sustain life on our planet (via Live Science). Almost all living organisms depend on the sun's energy to stay alive. But as the saying goes: That which nourishes me destroys me (via In search of Christopher Marlowe: a pictorial biography). While a bit of sunshine can be healthy, there's no denying that UV radiation can be savage on your skin. Besides exacerbating ageing, the sun's rays can contribute to developing skin problems like acne, dark spots, and dry, irritated skin (via Acne Intelligence). This might occur in part due to dehydration. Additionally, the sun's UV light overstimulates the sebaceous glands, which produce naturally occurring oil that helps lubricate your skin and keep it supple. But when excess sebum is created, it irritates the outer layer of your skin and throws it off-kilter. The sun can also increase inflammation and cause post-inflammatory hyperpigmentation (discoloration), which may give rise to acne breakouts (via WebMD). Indeed, people often report a "summer aggravation" in humid and sweaty environments, as noted by a 2014 study (via The Journal of Dermatology).

Prolonged sun exposure can also bring about "solar comedones," which appear as bumpy, flesh-colored papules (via Healthline). These blemishes tend to crop up on the cheeks of middle-aged and older people, but they're also found on frequent sun dwellers or people working in outdoor jobs, such as builders and farmers.

Could sunshine be the answer to a fast and healthy metabolism? According to a study from the journal Scientific Reports, the sun's blue light rays may help shrink fat cells in the body, and in turn, aid weight loss and allow your metabolism to operate effectively. Some researchers chalk this up to vitamin D, which is naturally produced when the sun shines on our skin (via Healthline).

The study findings are reinforced by the fact that people tend to put on more weight in the darker, winter months. Night work also appears to have metabolic consequences, as reflected by a study published in 2020, which found that shift workers like nurses and midwives generally have higher BMIs than those who work in ordinary daytime jobs (via Diabetology & Metabolic Syndrome). People who work during the night produce less leptin, a hormone that sends a signal to your brain to let it know when it's time to stop eating (via PLoS ONE). They also have increased levels of cortisol and ghrelin — stress hormones that contribute to weight gain. What's more, individuals who change from working at night to working in the day have been found to lose weight.

Everyone knows that too much UV radiation can cause life-threatening skin cancer, but it turns out that the sun might actually help prevent other cancers. Research has shown that people residing in places with fewer daylight hours have a greater chance of developing cancer than those who live in a sunnier climates. After all, the sun is one of our main sources of vitamin D, which can have anti-inflammatory effects and slow down tumor progression (via JAMA Network Open). A 2016 review of the risks and benefits of the sun confirmed that this glowing entity can indeed significantly reduce the risk of cancer, which may "at least in part" be attributed to vitamin D. Once Vitamin D is concocted in the skin, it makes its way to the liver and kidneys via the blood, where it's converted to calcitriol — an active form of vitamin D — which has various vital functions in the body (via ScienceDirect).

Another 2014 study showed that people with vitamin D deficiency have a greater chance of dying from various types of cancer compared to people with adequate levels of it, and vitamin D produced by the sun appears to be far more potent than the version achieved by taking supplements (via The BMJ). Still, it's important to take care not to burn — the GrassrootsHealth Nutrient Research Institute recommends covering up or applying non-toxic sunscreen, and avoiding excess exposure during the hottest hours of the day.

Yeah, you heard that right — sunlight may actually be an elixir for longevity. Sunbathers (who don't overdo it) get to live longer than those who shun the sun's rays as much as possible, reports a 2016 study. The researchers discovered that women who spent more time in the sun had longer lifespans — including less heart disease and fewer non-cancer deaths — than those who consistently avoided the sun. There are some important caveats, the authors note: Sun-goers lived somewhere between seven months to two years longer than those who stayed out of the sun, so the benefits of sunshine are relatively small in the grand scheme of things. Also, the impact of sunshine on longevity needs further investigation.

Another 2017 study revealed that mortality rates in the U.S. are 25% higher in the winter than in the summer. And although lighter-skinned people are more likely to develop skin cancer, people with darker skin are more prone to vitamin D deficiency — due to the melanin in their skin blocking the UV radiation that promotes vitamin D creation — and therefore are more likely to develop or die from a number of health conditions (via Nutrients). Additionally, a 2020 meta-analysis showed that melanoma patients with lower vitamin D levels had a 55% higher mortality rate (via the Journal of the European Academy of Dermatology & Venereology).

The general public health message of sun avoidance should be changed to encourage people to take measures to avoid sunburn instead, suggests a 2020 review study. For instance, they advise that people should be mindful of the time they spend outside during peak daylight hours.

Who would've thought that when UV light hits your skin, it can set off a domino health effect that extends to your heart? A 2020 study of 342,000 patients at dialysis clinics across the U.S. found that exposure to the sun resulted in lower blood pressure readings, irrespective of temperature. This is because sunlight triggers the release of "nitric oxide" from our blood vessels, explain the researchers. This powerful, endogenous compound relaxes your blood vessels and causes them to dilate, leading to lower blood pressure and driving down the risk of cardiovascular problems like a stroke, heart attack, heart failure, and peripheral arterial disease.

Other studies identify scarce levels of vitamin D as a potential contributing factor to poor heart health. As detailed by a 2019 review study, insufficient vitamin D might actually elevate blood pressure and increase people's risk of hypertension and heart disease. But the evidence for the relationship between the sunshine vitamin and cardiovascular risk is still in its infancy, says Erin Michos, director of the Johns Hopkins Women's Cardiovascular Health Center, per John Hopkins Medicine. Michos says, "We don't know for sure whether treating with vitamin D can prevent a heart attack" in quite the same way that we know that "vitamin D is good for the bones."