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Vitamin D Deficiency Linked to Heart Attacks

More than 75 years ago, we learned that lack of vitamin D causes rickets, bone deformities and failure to grow in children. Twenty years ago, reports started to appear showing that lack of vitamin D also impairs your immunity to limit your ability to kill germs. This was followed by studies showing that it also increase risk for certain cancers. Now the Framingham Offspring Study from Harvard tells us that low blood levels of vitamin D increase risk for heart attacks (Circulation, January 2008).

The authors followed 1700 participants (mean age 59) without prior cardiovascular disease for five years. Those with low blood levels of active vitamin D at the onset had one and a half times the chances of suffering a heart attack. Those with low vitamin D and high blood pressure had twice the risk. At this time, nobody knows why lack of vitamin D increases heart attack risk.

Dietary sources of vitamin D include deep-water fish and fortified cereals, but most North Americans meet their needs for vitamin D from sunlight and not from their diets. If you do not get out in the sun at least a few times a week, ask your doctor to check your blood levels of vitamin D. People with dark skin and those who are overweight are most likely to be deficient.


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Dear Dr. Mirkin: How can I keep from getting tired on long bicycle rides?

Anything you can do to strengthen your legs will make you more efficient when you ride. Research from Norway shows that the stronger you are, the slower and more efficiently you pedal when you are going at a relaxed pace (European Journal of Applied Physiology, November 2007). Fourteen healthy subjects performed supervised heavy lifting (two sets of the heaviest weight that they could lift 12 times in a row) for 12 weeks, including two days per week of squats and leg curls. They improved by 20 percent in the squats and 12 percent in their leg curls. At the end of the study, their increased strength caused them to use a pedal rate that was about 10 revolutions per minute slower during cycling at half their maximal power output. They used three percent less energy to do this.

When you are trying to go as fast as you can, use a fast cadence between 80 and 100 revolutions per minute. However, when you are sightseeing, pedal at 60 to 70 revolutions and you will use less energy to go the same distance.


Dear Dr. Mirkin: Does caffeine really improve athletic performance, or do you just feel more alert?

In endurance events, the first cause of fatigue is loss of muscle sugar, so athletes do whatever they can to preserve sugar levels. Caffeine causes the body to produce large amounts of adrenalin, which causes fat to be released from fat cells and float in the bloodstream. This extra fat is taken up by the muscles and used for energy, thus preserving the body's limited stored supply of muscle sugar. When muscles run our of sugar, the athlete requires more oxygen to do the same job, slows down, fatigues earlier, and has difficulty maintaining his performance.

A questionnaire from competitors at the 2005 Ironman Triathlon World Championships showed that seventy-three percent of the athletes believe that caffeine improves performance and 84 percent believe it improves concentration (International Journal of Sport Nutrition and Exercise Metabolism, August 2007). During competition, 65 percent used cola drinks and 24 percent used caffeinated gels. Although caffeine can increase risk for heat stroke and theoretically can cause irregular heartbeats, almost none of the athletes reported suffering any side effects from taking caffeine.


Recipe of the Week

Make a big pot of chili for Superbowl Weekend (or any time!)

Chili for a Crowd
Harlan's Dad's Chili
Squash Chili
Extra-Quick Chili

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

June 25th, 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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