The Science Behind the Sun

As we approach Easter time, many of us will be noticing the blooming flowers and longer, sunnier days- for many of us, a reason to rejoice! The better weather definitely seems to cheer people up and boost ice cream sales, and whilst most people know to some degree that catching a bit of sun can both benefit and harm health, sun protection advice is increasingly ignored by teens wanting to tan and children wanting to play out in the sun. So I’m here to educate and tentatively advise a little bit about the sun.


As most people can confidently tell me, sunlight is a great- the best, in fact- source of vitamin D. But what is vitamin D? For one thing, it’s not technically a vitamin. Vitamins are generally defined as organic chemicals that are obtained from a person’s diet because they’re not produced by the body. Yet vitamin D is produced by the body and about 90-95% of it is obtained through sunlight. Also, it isn’t found in any natural foods except egg yolks and fish. Still, old habits die hard so it’s referred to as a vitamin even so.

Vitamin D is obtained from sunlight by using the sun’s ultraviolet B energy to turn a chemical in your skin into vitamin D3. D3 is then carried to your liver and kidneys, each time picking up oxygen and hydrogen molecules, to finally become 1,25(OH)2D aka calcitriol or vitamin D.

Now what vitamin D actually does is a bit more interesting. It’s best-known role is to keep bones healthy. The way it does this is by increasing the amount of calcium that can be absorbed in the intestines. Without enough vitamin D, the body only absorbs 10-15% of the calcium in our diets whilst 30-40% can be absorbed with the right amount of it. It also helps the body to absorb phosphate in our diet, which is also required for bone health.

Without sufficient vitamin D, bones can become soft and weak leading to bone deformities like rickets in children. Rickets is no longer as common as it used to be, but it causes bone pain, poor growth and deformities of the skeleton.


Sunlight has many other benefits, such as mood improvement. Exposure to sunlight can increase the brain’s release of the hormone serotonin, which is associated with mood boosting and a deficit of serotonin can lead to depression. There is also a correlation between the number of deaths from heart disease in the summer as opposed to the winter suggesting that the sun can reduce heart disease. UV radiation from sun exposure can be used to treat eczema (dry itchy skin), jaundice (yellowing of skin and whites of eyes) and acne and is sometimes recommended by doctors if they think light treatment would help. Finally, a moderate amount of sunlight may prevent cancer. According to a study from Environmental Health Perspectives, people who live in areas with less sun/daylight hours are more likely to have a variety of cancers including ovarian, pancreatic and colon cancer. However, too much sun can also cause cancer so it’s important to get the right balance.


As too many people have experienced first hand, staying out in the sun too much without protection can cause sunburn which not only is painful but also increases your chance of getting skin cancer. Sunburn is caused by the UV light from the sun which can damage the DNA in cells. As a result, the cell with damaged DNA ‘commits suicide’ (apoptosis). Cancer can occur if cells with damaged DNA do not die as they should, but instead continue to multiply. According to the Skin Cancer Foundation, people who have had 5+ sunburns have twice the risk of developing skin cancer. Another thing to be aware of is you can still get sunburnt in the UK and/or if it’s cloudy.


Heat exhaustion and stroke are two other serious conditions that can happen when you get too hot, sometimes from being in the direct sun but other times just from being in a hot climate.Heat exhaustion describe the condition in which you become very hot and begin to lose water and/or salt from your body leading to feelings of weakness, dizziness, sickness and various other symptoms.

If heat exhaustion is not treated it can lead to heatstroke, which is when your body can no longer cool itself so your body temperature becomes dangerously high. This puts a strain on multiple organs including the brain, heart and lungs and can be life-threatening. If you have heatstroke, symptoms of heat exhaustion can develop into more serious symptoms like seizures (fits) and loss of consciousness.

If a person displays signs of heat exhaustion, you should try to cool them down by moving them to a shaded or air conditioned area, using a wet flannel to cool their skin and rehydrating them. However, the best advice that can be given is to not get heat exhaustion, heatstroke or sunburnt in the first place.


To ensure you are safe in the sun, you should spend time in the shade when the sun is at it’s strongest (between 11am-3pm in the UK) and use at least factor 15 suncream. Even if you are wearing water resistant suncream, it should be reapplied after you’ve been in water or if you’ve been sweating. You should protect your eyes using sunglasses with the CE mark and wear a wide-brimmed hat to shade your face and neck. Children are especially at risk as their skin is more sensitive than adult skin, so children should be encouraged to play in the shade, cover up in loose cotton clothes and wear lots of suncream. Finally, you should not spend a longer time in the sun wearing suncream than you would normally spend without it- my mum’s general rule of thumb is to limit it to 20 minutes of being in direct sunlight at any one time.


Whilst the sun does present some dangers, it’s warmth is also essential for human life to even exist and I still encourage you to enjoy it this spring and summer. All I ask is that you do so sensibly, because no sane person enjoys sunburn and heatstroke.


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