What is vitamin D?
Known as the sunshine vitamin, vitamin D is technically a hormone that’s produced when skin is exposed to sunlight – specifically UVB. The problem is that we’ve become so successful at protecting ourselves from the sun (SPF30 reduces vitamin D production by 97.5 per cent) that our vitamin D levels have plummeted, and it’s virtually impossible to top them up through diet. “Basically, the entire world population is deficient in vitamin D,” explains Dr Michael F. Holick, director of the Heliotherapy, Light and Skin Research Center at Boston University, and author of The Vitamin D Solution.
What does vitamin D do?
“Two thousand of the 26,000 genes in the human genome are positively affected by vitamin D,” says Dr John J. Cannell, founder of America’s Vitamin D Council. Multiple chronic diseases are now associated with vitamin-D deficiency, including auto-immune disease, type 1 and 2 diabetes, multiple sclerosis, rheumatoid arthritis, heart disease and Alzheimer’s.
Vitamin D is also a player in cancer prevention. “We did a study in healthy adults on 2,000 units of vitamin D a day, and we discovered it affected 291 genes responsible for DNA repair, auto-oxidation, immune function and a whole variety of metabolic processes,” explains Dr Holick. “If a cell starts to become malignant, active vitamin D first tries to normalize it, and if it can’t, it sends a chemical message for it to die.”
And if you need an immunity boost, research by Dr Cannell shows that vitamin D supplements prevent flu more effectively than the standard vaccinations.
How much vitamin D should I take?
Unless you spend part of every day of the year outdoors in brilliant sunshine, without sun protection, and with bare arms and legs, you will be low on vitamin D. Every expert we spoke to supplements with vitamin D, but the amounts they take vary. Dr Holick takes a daily supplement containing 4,000 units or IUs (International Units) of vitamin D3, which is more efficient than D2, while Dr Cannell takes as much as 10,000 units. “I recommend 3,000 units of vitamin D to my patients,” explains Dr Horlick. “But as an absolute minimum, adults should be taking 2,000 units a day.” Be reassured that there is little danger of overdosing on vitamin D. “You would have to take 50,000 to 100,000 units of vitamin D every day for six months before you had cause for worry,” says Dr Horlick.
Vitamin D supplements are proven to deliver the same benefits as sun exposure, so you don’t need to risk other ailments to top up a deficiency – protecting skin with SPF every day is still essential.
SHIELD YOUR SKIN
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