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Taking Sugar When You Exercise Is Good for You

Last week's eZine showed how eating refined carbohydrates and drinking sugared liquids at rest can cause high blood sugar levels, increasing risk for diabetes, heart attacks and premature death. However, during exercise, sugared drinks help you move faster and stronger. It is usually safe to take sugared drinks while you exercise because blood sugar levels rarely rise too high during exercise or for an hour afterward. Contracting muscles draw sugar so rapidly from the bloodstream that there is no sharp rise in blood sugar.

• Contracting muscles help to prevent the high rise in blood sugar that follows eating refined carbohydrates during rest (1).
• Unlike resting muscles, contracting muscles do not require insulin to move sugar inside their cells (2).
• Contracting muscles remove sugar maximally from the bloodstream, without needing insulin, during & up to one hour after exercise. The effect tapers off to zero at about 17 hours (1),(3),(4).

How fast you can run, swim, ski, skate, cycle or move your muscle in any sport depends on the time it takes to move oxygen from your lungs into your muscles. Anything that reduces your oxygen requirements will help you to move faster in sports. Your muscles burn carbohydrates, proteins and fats for energy. However, carbohydrates (specifically the sugar, glucose,) require the least oxygen to power your muscles. Anything that sends sugar rapidly into your bloodstream increases passage of sugar into muscles and helps them to burn a greater percentage of sugar so you can move your muscles faster with greater strength.

Sugared drinks provide sugar to your muscles much faster than sugared solid foods. When food enters your stomach, the pyloric sphincter closes and the stomach can squeeze only the soupy liquid into your intestines. Sugared liquids enter your intestines immediately while some sugared foods can stay up to five hours in your stomach.

Recent data show that glucose-fructose drinks are far more effective than plain water or drinks that contain just glucose in leaving the stomach faster and bringing fluid into the bloodstream faster to improve hydration during intense exercise. (Scandinavian Journal of Medicine & Science in Sports, February 2010). Therefore the best drinks to maintain endurance are those that contain glucose and fructose. Exercise drinks made with high fructose corn syrup (HFCS) may have an advantage over those sweetened with cane or beet sugar.

ALL sugared drinks should be consumed only during exercise or immediately after. When you are not contracting your muscles, quench your thirst with water or no-calorie beverages.

(1) Am J Clin Nutr 2008(July);88(1):51-57
(2) J Appl Physiol 2005;99: 338-343 & 2005;8750-7587
(3) Am J Physiol Regul Integr Comp Physiol 1983;245(5)
(4) Journal of Applied Physiology, February 2010


Dear Dr. Mirkin: Do women sweat less than men?

Yes. A study from Japans shows that women need to work much harder than men to start sweating during exercise. (Experimental Physiology, October 2010). You start to sweat when your body heat reaches a certain temperature. Men start to sweat earlier than women do because they start to sweat at lower temperatures.

You sweat to cool your body. Most women have less body fluid than men, so they become dehydrated more easily, and dehydration can kill. Sweating later and at higher temperatures is an evolutionary adaptation for women to lose less fluid so they can survive fluid loss in hot weather.

Sweating lowers body temperature. Almost 80 percent of the energy you use to power your muscles during exercise is lost as heat. The harder you exercise, the more heat you generate. Increasing body temperature increases your muscles' requirements for oxygen, so the higher your body temperature, the more oxygen your muscles need to move your body. Anything that increases need for oxygen weakens you and slows you down. Men usually have larger muscles. Starting to sweat at lower body temperatures prevents a rise in body temperature so they can move faster and with more strength.

Out-of-shape people start to sweat later than fit people do. As you become more fit, you sweat earlier in your exercise, at lower temperatures, and lose more fluid through sweating. The untrained women in this study had the most delayed sweating response, required higher body temperatures to start sweating, and did not sweat as much. See also Why you sweat more after exercise


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Dear Dr. Mirkin: Can you take too many fish oil pills?

Yes! Your immunity produces chemicals that dissolve the outer membranes on bacteria to kill them and rid them from your body. Inflammation means that your immunity stays active all the time, so the same immune mechanisms can dissolve parts of your body to increase risk for heart attacks and certain cancers. For example, people with inflammatory bowel disease (associated with a markedly overactive immunity) are at increased risk for developing colon cancer.

Omega-3 fish oil is good because it helps to decrease an overactive immunity that causes inflammation. However, when you take large doses of factors that limit your immunity, you can suppress your immunity enough to make it more susceptible to infections that can damage your body. A study from Michigan State showed that fish oil supplements increased the incidence of colon cancer and infections in mice susceptible to inflammatory-like bowel disease and some developed colon cancers within four weeks of taking fish oil supplements (Cancer, October 2010). Fish oil supplements made the test mice less able to mount a successful immune response to kill bacteria that increase colon cancer risk. In a like manner, several studies show that beta-carotene (provitamin A) pills increase lung cancer rates in smokers.

Thousands of studies show that eating fish is associated with reduced risk for heart attacks and certain cancers. Fish oil pills are most helpful in people who lack a dietary source of fish oil. The authors state: "People already receiving enough omega-3 fatty acids through their normal diet and foods have no need for added supplementation."


Recipe of the Week:

A wonderful fall vegetable stew --
Tagine with Pumpkin & Vegetables

Try making your own spice mix for this recipe and many others:
Spice Blends

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

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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