“Ladies and Gentlemen of the class of 20071, if I could offer you only one tip for the future, sunscreen would be it. The long-term benefits of sunscreen have been proved by scientists, whereas the rest of my advice has no basis more reliable than my own meandering experience….”
That’s sound advice from the track Everybody’s Free (To Wear Sunscreen) as we head towards the summer vacation and spend more time outside, playing sports, relaxing in the garden, on the beach or around the pool.
We’ve all been warned about spending too long exposed to the sun. Not only will our skin burn but we also increase the risk of damaging our skin permanently: exposure to ultraviolet (UV) rays in sunlight sun without adequate protection can damage DNA in skin cells. While occasional damage to DNA is normally repaired by the body, long-term exposure to UV can cause irreparable damage: for instance, uncontrolled growth of abnormal cells is manifested as skin cancer.
Medical organizations recommend using sunscreen because it helps avoid developing squamous cell carcinomas and basal-cell carcinomas: the latter originate from the lowest layer of the epidermis, and represent the most common but least dangerous form of skin cancer; the former originate from the middle layer and are less common but more likely to spread and, if untreated, become fatal.
Note, however, many sunscreens do not block UVA radiation, which does not cause sunburn but can increase the rate of melanoma, another kind of skin cancer, and photodermatitis. Melanoma, which originates in the pigment-producing cells (melanocytes), is the least common, but most aggressive, most likely to spread and, if untreated, become fatal. Using a broad-spectrum (UVA/UVB) sunscreen can help. The good news is that melanoma also has one of the higher survival rates among major cancer, according to data from Cancer Research UK.
Not overdoing it in the sun is not just sound medical advice but makes a difference to our appearance too. Exposure to the sun ages the skin’s appearance, making it more mottled; freckles can turn into brown sun spots; the skin takes on a dry, leathery appearance; and wrinkles and sagging increase. In contrast, a study has shown that diligent use of sunscreen can also slow or temporarily prevent the development of wrinkles and sagging skin.2
Inevitably, however, the story is not as simple as that. There’s also evidence that too little exposure to sunlight can increase the risk of cancer. Sunlight is well known as a promoter of Vitamin D that is essential to our health. If we don’t make enough of this ‘sunshine vitamin’ by exposing our skin to sunlight, we need to ensure we get plenty of oily fish and mushrooms in our diet. One recent study showed that women with sufficient levels of vitamin D were 77% less likely to develop breast cancer. Not getting enough vitamin D has also been linked to MS (multiple sclerosis), diabetes, pancreatic cancer, prostate cancer and a range of other cancers and diseases.
Our diet is linked to the way we react to sunlight in more ways than one, though. One informal study has concluded that eating tomatoes could also protect our skin from UV damage from sunburn: the active ingredient is the antioxidant lycopene. A 12-week course of eating 55g of tomato paste everyday (providing 16mg of lycopene)reportedly resulted in a 30% increase in skin protection amongst the women who took part.
Like all health science, the amount of sun we can tolerate depends on many complex variables but, as the song goes: “Trust me on the sunscreen….”
Note that the ‘strength’ of the sun varies according to:
- Sun height – the higher the sun in the sky, the higher the UV radiation level. UV radiation varies with season and time of day, with maximum levels occurring when the sun is at its maximum elevation, at around midday (solar noon) during the summer months.
- Latitude – the closer the equator, the higher the UV radiation levels.
- Cloud cover – UV radiation levels are highest under cloudless skies. Even with cloud cover, UV radiation levels can be high due to the scattering of UV radiation by water molecules and fine particles in the atmosphere.
- Altitude – at higher altitudes, a thinner atmosphere filters less UV radiation. With every 1,000 metres increase in altitude, UV levels increase by 10% to 12%.
- Ozone – ozone absorbs some of the UV radiation that would otherwise reach the Earth’s surface. Ozone levels vary over the year and even across the day.
- Ground reflection – UV radiation is reflected or scattered to varying extents by different surfaces. For instance, snow can reflect as much as 80% of UV radiation, dry beach sand about 15%, and sea foam about 25%.
1This is the 07 mix.
2’Sunscreen and Prevention of Skin Aging’ 158 (11). Annals of Internal Medicine. 4 June, 2013. pp. 781–790.