Sunlight or vitamin D?By Rafael Castillo M.D.
Philippine Daily Inquirer
Showing me a bottle of vitamin D given by her relative from the United States, a 54-year-old patient asked me recently if it’s advisable for her to continue taking it or not.
She had a noticeable fair skin, and it was quite obvious she was under the care of a dermatologist. I asked her if she was getting enough sunlight regularly, and she replied that it would ruin her skin and her dermatologist had strongly advised her to avoid the sun.
In fact, she applies sunblock cream before she goes out every morning. “I’m spending a lot to keep my skin looking good and what a waste it would be if I let the sun ruin it,” she quipped.
Vitamin D is naturally obtained from sun exposure, and people who get adequate sunlight do not need vitamin D supplements because sunlight promotes sufficient vitamin D production in the skin.
It is called a provitamin because it is biologically inactive as it is, and has to undergo two reactions to become active in the body. The active form of vitamin D in the body is called calcitriol, which promotes the absorption of calcium and phosphorus from food in the gut and reabsorption of calcium in the kidneys. Enough calcium in the body prevents brittle bones which can make one susceptible to fractures.
Aside from maintaining healthy bones, calcitriol also plays a key role in the maintenance of many organ functions. Over the last 15 years, there have been so many published researches demonstrating other benefits of vitamin D. Among these are:
• It helps boost the immune system and protects one from infections including common colds, as reported by scientists from the University of Colorado Denver School of Medicine, Massachusetts General Hospital and Children’s Hospital Boston.
• It has also been linked to maintaining a normal body weight, according to research carried out at the Medical College of Georgia, United States, so some weight reducing clinics are prescribing it for their patients.
• It can help reduce asthmatic attacks and hospitalizations due to asthma, based on published data from the Harvard Medical School.
• It can also help maintain normal functioning of the brain, perhaps preventing dementia, according to a study of 3,000 European men between the ages of 40 and 79.
• It can accelerate the healing from chronic infections like tuberculosis, as recommended by a study published this year in the Proceedings of the National Academy of Sciences.
• It can possibly help prevent cancer, since vitamin D deficiency was associated with cancer, regardless of nutritional status, in a study conducted by Cancer Treatment Centers of America.
• It may help prevent heart attacks and premature deaths, based on a study published just last month.
I think we have enough scientific evidence to recommend vitamin D, but we must remember that it is not water-soluble and taking too much of it can also have side effects because our body can’t easily excrete the excess, as we do with water-soluble vitamins like vitamin C.
According to the Food and Nutrition Board at the Institute of Medicine of The National Academies, which created the Dietary Reference Intakes (DRIs), the following doses are recommended for those with no sunlight exposure:
• Children up to 13 years — 5 mcg (200 IU);
• 14-18 years — 5 mcg (200 IU);
• 19-50 years — 5mcg (200 IU);
• 51-70 years — 10 mcg (400 IU); and
• 71+ years — 15 mcg (600 IU).
“All you need is 15 minutes of sunlight exposure—either early morning or late afternoon—three to four times a week to have enough vitamin D levels in your body,” I told my patient. She didn’t answer, and obviously, there was no way she would follow my recommendation.
“Then you need to take your vitamin D supplements,” I advised.
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