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Dr. Mirkin: Vitamin D

Posted April 4, 2008 at 04:00 PM by Alexandra Haller

Section: Her Health, Injury & Rehab, Her Nutrition, Healthy Eating, Supplements

Over the last few years I have reported on numerous studies linking vitamin D deficiency with various diseases: diabetes, heart attacks, at least 30 types of cancer, and autoimmune disease such as lupus and rheumatoid arthritis.

People get most of their vitamin D from sunlight.  The skin has an enormous capacity for vitamin D production and supplies the body with 80-100 percent of its vitamin D.  However, a recent study showed that a high percentage of people in sunny Arizona are vitamin D deficient (American Journal of Clinical Nutrition, March 2008). How can this be?  A clue to the problem is that a large percentage of the people who were deficient were African-American, Hispanic, elderly or overweight.  We know that people who have dark skin need more vitamin D because dark skin blocks the sun’s UVB rays that make vitamin D. Another study showed that almost 50 percent of African Americans in Boston had low vitamin D in March.  We also know that obesity can cause vitamin D deficiency because body fat removes vitamin D from circulation.  Furthermore, as people age, skin cannot synthesize vitamin D as efficiently and the kidneys are less able to convert vitamin D to its active hormone form.

An article from Australia showed that 15 out of 18 young gymnasts in Australia suffered from vitamin D deficiency (Clinical Journal of Sport Medicine, March 2008).  These athletes spend a lot of time training indoors.  Even if you spend several hours a day outside in winter, you probably will not get enough sun to meet your vitamin D needs.  At our latitude the sun’s rays reach earth at an angle so they have to penetrate a thick layer of the
earth’s atmosphere and fewer rays get through.  Also, when the weather is cold we cover most of our skin with clothing.

My personal plan and recommendations

While we wait for the scientific community to resolve whether lack of vitamin D causes cancers, heart attacks and so forth, or is just a marker for other risk factors such as lack of activity or excess weight, I think you should be aware of your own
vitamin D status and take action if you are deficient. If you seldom go outdoors, have dark skin, are over 50 or are overweight, I recommend that you ask your doctor to do blood tests for vitamin D3 and D2.  D3 is made by your skin from ultraviolet light (UVB) or from the vitamin D you get in foods or supplements.  D2 comes just from food or supplements.  Your total blood level of vitamin D should be over 50.  If it is below 50, you may need to take a tropical vacation, use a tanning bed or take vitamin D supplements.  A safe dose appears to be 1000 IU per day during the winter.

This post is written by Dr. Gabe Mirkin, M.D. and used with permission.  Dr. Mirkin is board certified in Sports Medicine and has practiced for over 40 years. He has completed more than 40 marathons and was a talk show host of a nationally-syndicated radio program for about 25 years. For more articles by Dr. Mirkin, click here.

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Tags: blood tests, dr. mirkin, health, injury prone, sunlight, sunshine, supplements, vitamin d, vitamin deficiency, vitamins, winter

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