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Sugar and Caffeine for Competition

The limiting factor to how fast you can move during a race is the amount of oxygen that you can take in and use. Since sugar requires less oxygen than fat to power your muscles, you want to get as much sugar into your muscles as quickly as possible. Anything that increases the amount of sugar that can be absorbed from your intestines into your bloodstream will help you ride or run faster and longer.

Sugar is carried across your intestinal tract into your bloodstream by special protein transporter molecules. Glucose has its own specific transporter protein and so does another sugar, fructose. So your muscles use 165 percent as much sugar when you take in glucose and fructose, compared to taking in only glucose. To put it another way, when you take in drinks that contain only glucose, your muscles can absorb and use only one gram sugar per minute, compared to 1.75 grams per minute when you take a drink that contains both glucose and fructose (Current Opinion in Clinical Nutrition and Metabolic Care, July 2010).

Furthermore, adding caffeine to a drink can increase absorption of sugar into the bloodstream by as much as 26 percent (Journal of Applied Physiology, June 2006).

The most effective drinks for endurance competition therefore may be those that contain glucose, fructose and caffeine, such as are found in many carbonated drinks. These drinks are safe during exercise because contracting muscles can prevent a high rise in blood sugar levels by drawing sugar from the bloodstream without needing insulin. However, when you are not exercising, these drinks can cause very high rises in blood sugar, increasing risk for obesity and diabetes.

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Dear Dr. Mirkin: Is breast cancer inherited?

Perhaps five to ten percent of breast cancers have known genetic cause. However, a recent study in Cancer Epidemiology (January 18, 2011) shows that nearly "Thirty percent of breast cancers can be prevented by modifying certain lifestyle habits." The most significant lifestyle factors associated with breast cancer are *taking estrogen at the menopause and *not exercising. Other factors include being overweight and taking more than one drink a day. "Thirty-seven percent of postmenopausal breast cancers are caused by factors women can't change, such as family history of breast cancer, starting menstruation before age 10, starting menopause after age 55."

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Dear Dr. Mirkin: What can I do about painful cracking skin on my feet?

Try applying tape across the split skin to limit movement of the cracked edges. Let the tape fall off, as pulling it off may tear the skin even more. Friction irritates the cracks, causing more pain, so avoid loose slip-on shoes, sandals or any other footwear that causes friction. Do not file the skin as this can cause even greater thickening (called the Koebner phenomenon) that leads to cracking.

Your podiatrist can prescribe topical medications, such as urea-based creams or cortisone creams, to help heal the cracks. Cortisone creams should be used with caution since they can cause permanent thinning of the skin. If your symptoms are severe, your doctor may recommend cortisone injections, but again be aware of the side effects of too much cortisone.

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Recipe of the Week: Chili for a party --

Chafing Dish Chili

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

January 30th, 2011
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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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