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Vitamin D Deficiency May Be Genetic

A report from University of Toronto shows that genetic factors cause some people to develop severe vitamin D deficiency while others do not (Clinical Biochemistry, July 2009). An earlier study showed that some people and mice have abnormal Vitamin D binding protein (VDBP) and therefore cannot respond to vitamin D normally (Endocrine Reviews, June 2008). They are at increased risk for heart attacks, strokes, certain cancers, depression, athletic injuries, muscle weakness and so forth.

Over the years I have been unable to run effectively in the winter and injuries forced me to miss six Boston Marathons. This same pattern of winter-time weakness and injuries plagued me when I switched to cycling. It wasn't until a few years ago that I drew blood and found that my vitamin D3 (Cholecalciferol) was 22 nmol/L (normal is greater than 75). Taking as much as 3000 IU of vitamin D failed to get my blood levels much over 30. I moved to Florida and rode my bike very well last winter. This winter was extremely cold and often cloudy, and my injury and weakness pattern recurred from January through March. I notice that a good day in the sun allows me to ride well for about three or four days, but the weakness and injuries recur until the next day of warm sunlight. My skin has never been damaged by sunlight, has no pre-cancers and looks much younger than my 74 years.

Vitamin D deficiency is associated directly with muscle weakness (Scandanavian Journal of Medicine & Science in Sports, October 2009) and athletic injuries (Current Opinion in Clinical Nutrition & Metabolic Care, November 2009; Molecular Aspects of Medicine, December 2008). It is my opinion that:

• Certain people are genetically susceptible to vitamin D deficiency
• These people are likely to be injured when they try to exercise vigorously in the winter
• Vitamin D pills will help some athletes, but many do not regain their athleticism at conventional doses
• These people may get better when they are exposed to sunlight during exercise. Of course they should be concerned about skin cancer from excess sunlight, but I think that people who are at high risk for vitamin D deficiency are at reduced risk for skin cancer. However, I have no available data to support that impression.


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Dear Dr. Mirkin: Does an exaggerated rise in blood pressure during exercise predict who will develop high blood pressure in the future?

For athletes, probably not. Many research articles have shown that people who develop very high blood pressure during exercise are the ones most likely to develop high blood pressure in later years (American Journal of Hypertension, April 2004). Textbooks explain that these people have arteries that do not expand as much as normal arteries when blood is pumped to them. When your heart beats, it squeezes blood from inside its chambers to the large arteries. This sudden bolus of blood causes normal arteries to expand just as balloons do when they fill with air. The walls of arteries have sensors that allow arteries to expand with each pulse of blood. If the arteries do not expand enough when blood enters them, blood pressure can rise very high. So exercise-induced systolic blood pressures greater than 190 in non-exercisers predict high blood pressure in the future. It's different for athletes who have the strongest hearts that push blood with the greatest force, so they have the highest rises in blood pressure during aerobic exercise (American Journal of Hypertension, November 1996). Blood pressure is determined by the force of the heart's contraction times the resistance in the blood vessels. Normal blood pressure is no higher than 120 when the heart contracts and 80 when it relaxes. During exercise, blood pressure increases markedly, with the highest blood pressures in experienced weight lifters occurring during a double-leg press where average values are 320/250 mm Hg, with pressures reported as high as 480/350 mm Hg (Journal of Applied Physiology, March 1985). It is normal for conditioned athletes to have blood pressures of 200/70 when they run on a treadmill.

The good news about exercise is that just 20 minutes of running on a treadmill or lifting weights lowers blood pressure for about seven hours of normal physical activity (Journal of Strength and Conditioning Research, November 2009).

Ninety percent of North Americans will develop high blood pressure, which increases risk for heart attacks, strokes, kidney damage and sudden death. If you have an exaggerated blood pressure rise during exercise and you are an athlete, you probably need only be concerned with your blood pressure at bedtime, but we have no good data on this. If it is above 120, you have high blood pressure and need to be treated.

However, if you are not a regular exerciser and your exercise-induced blood pressure is above 190, you should go on a heart attack prevention program that includes a diet that is high in plants and low in meat and refined carbohydrates, check with your doctor for clearance to start exercising regularly, lose weight if overweight, avoid smoke and stimulants or drugs that raise blood pressure.


Dear Dr. Mirkin: Has anyone shown that vitamin D pills can help to prevent heart attacks in people with a deficiency of that vitamin?

Yes. Researchers from the Intermountain Medical Center Heart Institute in Utah just presented two studies at the American College of Cardiology's 59th annual scientific session (March 15, 2010).

The first study was on 9,400 patients with average vitamin D3 levels of 48.3 nmol/L (normal over 75). At follow- up, the half who took pills to raise their vitamin D levels to normal were 33 percent less likely to suffer a heart attack, 20 percent less likely to develop heart failure, and 30 percent less likely to die.

In the second study, 41,000 patients were classified into normal, moderate deficiency, and severe deficiency of vitamin D. Severe deficiency put them at high risk for heart disease and strokes. Those who took vitamin D and raised their blood levels above 107 nmol/L had the lowest risk.


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June 21st, 2013
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About the Author: Gabe Mirkin, MD

Sports medicine doctor, fitness guru and long-time radio host Gabe Mirkin, M.D., brings you news and tips for your healthful lifestyle. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. He is board-certified in four specialties: Sports Medicine, Allergy and Immunology, Pediatrics and Pediatric Immunology. The Dr. Mirkin Show, his call-in show on fitness and health, was syndicated in more than 120 cities. Read More
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