Jetting off for some winter sun could leave you exposed to too much UV radiation
If you're stuck indoors, you may not be getting enough sun, and if you're off on a winter holiday, you may be exposing your skin to too much. And the problem, according to research from Penn State University, US, is our skin colour.
Because the colour of human skin has evolved over thousands of years, it isn´t able to cope with the way we live now. Living in different climates from those of our ancestors, as well as travelling to warmer or colder areas where we´re exposed to different levels of UV radiation, means that people are both at risk of too little and too much sunlight.
Professor Nina Jablonski, of Penn State, says that around 2 million years ago the human body developed its ability to utilise melanin to process sunlight - to help us absorb sunlight for vitamin D or to protect it against ultraviolet radiation when there is too much or we´re overexposed to sunlight.
However, as some groups of humans moved to more temperate climates north or south of the equator, the sun wasn´t so intense and so people developed lighter skin. But, says Jablonski, now people with naturally dark skin whose ancestors came from areas closer to the equator, live in areas where there isn´t much exposure to ultraviolet radiation and similarly those who have naturally lighter skin live in parts of the world where the sun is fierce.
What´s more, people are moving from one region to another within a day, whereas thousands of years ago, humans would move at most a few kilometers in the same time.
But it´s not just about where people are living, it´s also how people are living. In cities - where 60% of the world lives - people aren´t as exposed to sunlight – the use of electric light and working indoors means that many people may miss out on getting regular doses of sunlight completely. This is all the more so if someone has darker skin.
So what can you do about it, other than making sure you get regular time outdoors each day?
Make sure you get vitamin D via other means. Jabonskli recommends vitamin D supplements for people who are deficient. But, as signs of vitamin D deficiency can be extremely subtle – including tiredness, general aches and pains, it's best to get tested.
"There aren't any obvious signs of vitamin D deficiency unfortunately until it is too late, i.e. poor bone health," says dietician Dr Sarah Schenker (www.sarahschenker.co.uk). "Certain groups of people are recommended to take a supplement, however - older people, pregnant women, babies and young children and those with darker skin or who cover up when outside."
"Dietary sources include oily fish (older people can eat up to four portions per week)," says Schenker. "That includes mackerel, salamon, sardines, fresh tuna. Also mushrooms (leave on a windowsill in sunlight to boost their levels), fortified and enriched foods such as margarines, breakfast cereals, yogurt and eggs."
Ensuring that you get plenty of foods that contain vitamin D is another way to prevent yourself from becoming deficient – try eating fish and fish liver oils, as well as egg yolks.
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