Mind & Body

The Real Benefits of Vitamin D – And How To Get Enough

Most of us have worryingly low levels of vitamin D, yet it’s vital in helping to prevent many diseases, as well as supporting immunity, mood and more. SUZANNE SCOTT explains the benefits of vitamin D and how to top up


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%) 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 are the benefits of vitamin D and what does it 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 type 1 and 2 diabetes, multiple sclerosis, rheumatoid arthritis, heart disease and Alzheimer’s. Doctors have long believed that vitamin D could help prevent autoimmune disease, but the latest research from Brigham and Women’s Hospital in Boston confirms it, finding that 2,000 IU of vitamin D per day reduced the onset of autoimmune disease by 22 percent.

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. Additionally, research by Trinity College Dublin has found that vitamin D can also help to prevent chest infections, particularly in adults who are already deficient. In fact, in one study they looked at, vitamin D reduced the risk of chest infections to half in people who took supplements.

How to take vitamin D

While the best way to top up your levels of vitamin D is through supplementation, you can benefit further from small amounts in your diet. As for what to look out for, egg yolks, oily fish such as salmon and mackerel, and red meat, including liver, all contain vitamin D. Some foods, such as bread and some cereals, are even fortified with vitamin D. When it comes to supplementation, capsules, or a spray or tonic applied to your tongue, are pretty commonplace, with neither one better than the other. However, if you’re taking vitamin D orally, it is best taken after food to aid its absorption.

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.


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