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Check Vitamin D Levels this Winter

In this newsletter I have reported that low vitamin D levels are associated with increased risk for heart attacks, strokes, at least 17 different cancers, diabetes, autoimmune diseases, depression and osteoporosis. Adequate blood levels of vitamin D are thought to be over 75nmol/L. Researchers at the University of Toronto have now shown that in the winter, more than 93 percent of the people in Toronto have concentrations below 75 nmol/L, and 75 percent have concentrations below 50 nmol/L (BMC Public Health, September 26, 2008).

Only those with light skins had average vitamin D intakes exceeding the current Recommended Adequate Intake (RAI = 200 IU/day). Those with dark skin and/or excess weight had very low levels of vitamin D. Dark skin blocks ultraviolet light. Obesity sequesters vitamin D so it is not available for use. Aging also lowers vitamin D levels as the skin of older people doesn't make vitamin D as well as during younger years.

In the wintertime, I recommend getting a blood test called D3. If it is below 75 nmol/L, you need more sunlight or vitamin D pills. The blood test for the active form of vitamin D (1,25 dihydroxy-vitamin D) is of little value as it often is normal when a person has a severe deficiency. Lack of vitamin D causes the parathryroid gland to produce massive amounts of parathyroid hormone that causes these falsely high levels.


Reports from

Sleep apnea


Volunteers sought for a study on stretching: After last week's report on stretching, I received this note from Alan Roth, Ph.D., Stretch Study Coordinator for USA Track & Field:
"The jury is still out regarding pre-run stretching. There have been no large randomized studies to show that pre-run stretching helps prevent injury. It's true that it can help performance but at what risk? The first large randomized study of pre-run stretching is now underway. We already have about 2,400 runners registered and more than 1,200 have submitted their reports after three months of participation."
For more information and to sign up to be part of the study go to


Dear Dr. Mirkin: Almost everyone in my family is overweight; am I destined to be fat?

Nobody has to be fat, but some people may have to exercise for many hours just to control their weight. For example, a gene associated with fatness has been identified in the Amish who live near Lancaster, PA. A study from the University of Maryland shows that Amish men with that obesity gene who burned more than 980 calories per day through physical activity were not fat. The same applied to women who burned more than 860 calories per day (Archives of Internal Medicine, September 2008).

Exercise causes you to eat more food, but when you are very active, you do not increase the amount of calories to equal what you burn. For example, if your exercise program causes you to burn 1000 more calories per day, you will usually increase your food intake by about 500 calories, and probably significantly less than that.


Dear Dr. Mirkin: How can I tell if my bicycle seat is at the right height?

Bicycle riders quickly learn that setting their seats too low often causes knee pain, while setting it too high often causes back pain. Extensive previous research shows that to prevent injuries, you should set the seat so that your knee bends to a 25 to 35 degree angle; and to get maximum power from pedaling, you should set the seat at 109 percent of the distance from the ground to your groin (inseam length). These two methods produce different seat heights.

Researchers at the University of Central Arkansas in Conway found that a 25 degrees knee bend angle is best to improve performance and prevent injuries (Journal of Strength and Conditioning Research/National Strength & Conditioning Association, July 2008). However, if you have knee pain or back pain, adjust the seat height until it is comfortable for you.


Recipe of the Week

Butternut Squash-Fruit Casserole

You'll find lots of recipes and helpful tips in The Good Food Book - it's FREE

June 22nd, 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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