Whereas exposure to excessive levels of sunlight is detrimental to our health, moderate exposure can boost our physical and mental state. The aim is to enjoy the sun sensibly, to make enough vitamin D, while not increasing the risk of skin cancer.
Vitamin D is made in the skin with the help of sunlight, which is useful because there is very little found in typical dietary sources. To prevent deficiency of vitamin D, it is recommended to have 2-3 sun exposures per week. Each exposure should last 20-30 minutes and be to bare skin.
The following are some of the health benefits that exposure to sunlight can bring.
1) Improves the quality of sleep
Waking up in sync with the sun’s natural light switches off melatonin, a hormone made in your pineal gland, associated with sleep onset. This is the reason why you feel alert during your waking hours and tired at bedtime – and discombobulated when you cross time zones after a long-haul flight. It is, therefore, a good idea to open the curtains in the morning and avoid artificial light once the sun goes down.
People with irregular sleeping schedules often have trouble sleeping or feel tired during waking hours. Several studies have shown that chronic disruption of circadian rhythms can lead to weight gain, slower thinking, and other physiological and behavioural changes – analogous to the changes observed in people who experience shift work or jet lag.
2) Reduces risk of some cancers
Prolonged sun exposure increases the risk of skin cancer, but vitamin D is also known to be protective against several cancers, including of the colon, kidney and breast. In a study conducted by the US National Cancer Institute, it was found that high levels of sunlight were significantly associated with reduced mortality from breast and colon cancer. Similar effects were seen in the bladder, womb, oesophagus and stomach cancer.
3) Improves mood
Sunlight triggers the release of serotonin, a neurotransmitter that helps to regulate mood. It’s no surprise that spending time outdoors improves mood and relieves stress. Lack of sunlight exposure in some people can even trigger a type of depression known as a seasonal affective disorder, which is treated with light therapy.
4) Lowers blood pressure
Rates of hypertension tend to be higher in the winter and in countries farther from the equator, and a 2014 study published in the Journal of Investigative Dermatology provides a possible explanation: Exposure to sunlight causes nitric oxide in the skin to be absorbed into the bloodstream, which can help widen blood vessels and lower the pressure inside them.
5) Improves pregnancy and fertility
Reduced vitamin D levels during pregnancy have been shown to be associated with complications such as gestational diabetes and preeclampsia. Babies are also more likely to be born underweight. Of course, it takes two to be infertile. Male fertility may also get a boost from sunshine. A 2008 Australian study found that one-third of 794 men visiting an infertility clinic had a vitamin D deficiency. When this was corrected with sunshine and supplementation, there was a 75% drop in ‘sperm fragmentation’ and the men were more successful at conceiving with their partners.
6) Can help with some skin disorders
Sunlight can improve several skin complaints, such as psoriasis, eczema and acne. Indeed, eczema and psoriasis are sometimes treated with UV light (phototherapy). However, sunlight can aggravate other skin conditions, particularly rosacea.
7) Enhances the immune system
In a 2016 study published in the journal Scientific Reports, researchers found that low levels of blue light and UVA light, found in sun rays, boosts the activity of T lymphocytes, a type of white blood cell that can fight infection.
8) Improves the musculoskeletal system
It is common knowledge that vitamin D is important for healthy bones by helping the body absorb calcium. In a 2013 large Danish study, researchers found that having a history of skin cancer was linked to a lower risk of hip fractures. This may be because those who developed skin cancer also had prolonged sun exposure.
Vitamin D is also important to muscle health, and people with low levels are more likely to experience muscle cramps and joint pain.
9) Improves memory
In a 2018 study published in the journal Cell, researchers exposed a group of mice to UVB rays. This mock-sunlight increased levels of glutamate, a neurotransmitter involved in learning and memory processes. The UVB-exposed mice showed significant improvement in the object recognition tests and motor skills compared to the control mice. Although this effect was shown in mice, it could also be the same for humans.
10) Helps you shed fat
By getting sufficient sunlight between 8am and noon will help synchronise your circadian rhythm, optimising the metabolism and preventing excess weight gain. Serotonin not only improves our mood, but it also suppresses our appetite. It’s no surprise if you prefer lighter meals during warmer weather.
One last thing
There are of course risks associated with sunlight. Prolonged exposure causes damage to the epidermis and to other parts of the skin such as the supporting elastic tissue in the dermis. This damage is known as actinic (solar) elastosis, and gives the skin a baggy, wrinkled appearance.
A significant risk factor for malignant melanoma is sunburn, especially during childhood. Chronic sun damage does not appear to be a risk factor for malignant melanoma but it is for basal cell and squamous carcinoma, and lentigo maligna melanoma.
To summarise, try to have 2-3 sun exposures per week, but avoid the sun when it is strong; and when you think you’re exceeding the recommended limit, cover up, or use high-factor sunscreen.