Natural Light And Your Health

Overview

From the production of vitamin D to the regulation of our mood, sunlight plays a vital role in maintaining our health. As such, getting your daily dose of sunlight at the right time may actually help to lower your risks for health conditions such as high blood pressure, heart diseases, and bone problems.

Understanding natural light 

Natural sunlight consists of mainly 3 components:

1. Ultraviolet (UV) rays, which are electromagnetic waves that have a shorter wavelength compared to visible light, and are not visible to the eyes
2. Visible light spectrum, which is the range of electromagnetic waves that we are able to see with our eyes and which can separate into different colours when passed through a prism
3. Infrared radiation, which is electromagnetic waves that have longer wavelengths compared to visible light

UV rays can be categorised into UVA, UVB, and UVC, in the order of decreasing wavelengths. The UV rays that we most often come into contact with are UVA, and following that, UVB. UVC is usually absorbed by the ozone layer.

Nutrients from natural light

While not a direct source of vitamin D, sunlight is a crucial player in the synthesis of vitamin D in our body. UVB rays are the most important in inducing the production of vitamin D3 in the epidermis, the outermost layer of the skin. Vitamin D produced in the skin needs to be further processed in the liver and kidneys before it can be used by the body. Other cells in our body can also produce vitamin D, but the UVB-induced production of vitamin D in the skin remains the major natural source of vitamin D for our bodies.

The amount of vitamin D produced in the skin depends on several factors, including:²

• The level of sunlight, which is affected by the time of day, season and air quality
• Skin pigmentation - melanin acts as a ‘natural sunscreen’ which absorbs sunlight and reduces the number of UVB rays that can penetrate into the epidermis to induce vitamin D production
• The use of sunscreen 

Vitamin D has a significant role in maintaining our health. This is because vitamin D helps with the absorption of calcium and phosphorus. With sufficient levels of vitamin D, calcium and phosphorus absorption can be increased by 30–40% and 80%, respectively.¹ This ‘sunshine vitamin’ is important for the development and maintenance of strong bones and muscles. Therefore, vitamin D deficiency increases the risks for bone and muscle conditions such as rickets, osteoporosis, and muscle weakness. Vitamin D was also suggested to help in lowering the risks for many chronic diseases, including cancers, heart diseases, type 2 diabetes, and autoimmune diseases.^1,3 

Benefits and importance of natural light for our health

Our bodies need cues, and natural sunlight acts as the main cue that synchronises our body clock with external time. At the back of our eyeballs are neurons that are sensitive to light known as photoreceptors. They detect light and deliver the message regarding the time of day to the brain. Sunlight suppresses the release of melatonin in the brain, the primary hormone that regulates the sleep-wake rhythm. This is why getting enough sunshine during the day and avoiding light at night is important. 

Sunlight and melatonin also regulate other bodily rhythms, including the cyclical change in our body temperature, cortisol levels, and eating times. 

Sunlight plays a role in triggering the production of serotonin, a chemical messenger in the brain that is involved in regulating mood. Longer duration of sunlight exposure and longer daytimes in summer or spring can increase the availability and release of serotonin in the brain, which lead to a better mood.⁴ Seasonal affective disorder can be improved by making sure you are exposing yourself to sufficient levels of sunshine.⁵

Alongside inducing the production of vitamin D, UV rays can deliver health benefits beyond vitamin D’s biological functions. UVA rays were suggested to stimulate the release of nitric oxide from the skin into the bloodstream, which can dilate the blood vessels and lower blood pressure. This may also help reduce the cardiovascular risks for hypertension and even heart attack. 

Best time to have natural light for our health

Around 10am to 1pm is probably the best time to go out and get some sunshine with minimal risk of melanoma.^6,7 

It is important to note that continuous and even intermittent exposure to sunlight can cause sunburn to your skin and can increase the risks of skin cancer. It is recommended to spend not more than 5-30 minutes in the sun every day.³ You should not look directly into the sun and wear sunglasses where possible. Wearing sunscreen appropriately according to instructions may help you obtain enough sunlight while minimising the risk of skin cancers.

Disadvantages of natural light to our health

Despite its health benefits, it is no doubt that excess sunlight exposure is the main contributor to skin cancer risks. 

Sunburn is strongly associated with an increased risk for melanoma, the cancer of skin-pigment-producing cells (melanocytes), and keratinocyte cancers, the cancers of the major cell type of the epidermis.³ This is because when melanocytes and their DNA are damaged by sun exposure, these cells may become mutated and divide to form tumours. 

Chronic sun exposure was found to increase the risks for keratinocyte cancers, including squamous and basal cell carcinomas, which are 2 of the most common skin cancers.³

Summary

To make sure the amount of natural light you are exposing yourself to is healthy, it is important to maintain a balance. Sunlight is important for the production of vitamin D in the skin, which helps maintain bone and muscle health. Besides that, sunlight also regulates the production of melatonin and serotonin, which regulate body rhythms and mood, respectively. Overexposure to sunlight and sunburn, however, is associated with increased chances of skin cancers.