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What to Eat During Hot-Weather Competition and Exercise

To be able to exercise intensely in hot weather, you have to maintain water, sugar and salt in your body for the entire time you exercise. How fast you can ride, run, or exercise is limited by the time it takes to bring oxygen into your muscles. If you can increase the oxygen supplied, or decrease the oxygen needed, you can move faster. Since sugar requires less oxygen to power your muscles than fat or protein, anything that allows your muscles to burn more sugar and less fat will help you to move faster.

Taking extra sugar during a competition or intense exercise lasting more than two hours is far more important than what you eat before your event. The limiting factor to how fast and intensely you can exercise in events requiring endurance depends on how quickly you can get sugar into muscles during exercise. You can markedly improve performance in endurance sports by starting to eat and drink soon after you start exercising.

Do not take in sugar until at least five minutes after you start your competition. When you eat sugar and your muscles are not contracting, you get a high rise in blood sugar that causes the pancreas to release large amounts of insulin. This can cause a drop in blood sugar levels that can tire you. On the other hand, exercising muscles draw sugar rapidly from the bloodstream without needing insulin. So taking sugar during exercise usually does not cause the high rise in blood sugar levels that causes your pancreas to release large amounts of insulin.

The energy for your brain comes almost exclusively from the sugar in your bloodstream. When blood sugar levels drop, so do brain levels, and you feel tired and have difficulty coordinating your muscles.

Another reason why you have to take sugar during intense exercise is that there is only enough sugar in your bloodstream to last three minutes at rest. To maintain blood sugar levels, your liver constantly releases sugar into your bloodstream, but your liver holds only enough sugar to last about twelve hours at rest and far less than that when you exercise. When muscles run out of their stored sugar supply, it hurts to exercise and the muscles become difficult to control.


Don't wait to feel hungry: Hunger during exercise is a very late sign of not getting enough calories. By the time you feel hungry, your body will be so depleted of sugar that you will have to eat large amounts of carbohydrate-rich food just to restore your sugar supplies.

What to eat and drink: All carbohydrates are single sugars, or sugars bound together in twos, up to thousands and millions. Before any carbohydrate can be absorbed into your bloodstream, it must first be broken down into single sugars. Human intestines do not permit combination sugars to pass into the bloodstream, so the most effective way to increase endurance is to take sugar- containing foods and drinks during prolonged exercise.

Caffeine increases sugar absorption from the gut. Taking caffeine when you eat carbohydrate-containing foods and drinks can double your rise in blood sugar (Journal of Caffeine Research, April 16, 2011). A high rise in blood sugar causes all the side effects of diabetes: blindness, deafness, heart attacks, strokes and so forth. However, during exercise, caffeine can increase endurance (Medicine & Science in Sports & Exercise, July, 2010) by increasing the absorption of sugar from your intestines and by increasing the uptake of sugar by your exercising muscles by as much as 26 percent (Journal of Applied Physiology, June 2006). Caffeine is found in coffee, tea, chocolate, cocoa and caffeinated soft drinks.

CAUTION! Take caffeinated sugared drinks only during prolonged, intense exercise. Taking sugared drinks, with or without caffeine, when you are not exercising causes higher rises in blood sugars that increase risk for diabetes and cell damage. Read my comprehensive report on what to eat and drink before and during hot-weather competition


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Dear Dr. Mirkin: How can I prevent my child from becoming as nearsighted as I am?

Take him outside often. From 1970 to 2000, the incidence of nearsightedness has almost doubled, probably because growing children spend too much time indoors (Archives of Ophthalmology, June and December 2009). Nearsightedness is not caused by reading at a young age. It appears to be caused at least in part by not getting enough sunlight.

As an infant grows, the eyes adjust to the amount of available light. Sunlight sets the normal distance between the lens and the eye nerve called the retina. However, when a child spends most of his time under artificial lights, the eye accommodates to this decrease in light by extending the distance between the lens and the retina. This makes far away objects appear blurred and a person becomes nearsighted.


Update on colon cancer and red meat:

The World Cancer Research Fund (WCRF) reviewed 263 research papers associating lifestyle factors with colon cancer and issued an 850-page report advising people to limit their intake of red meats such as beef, pork and lamb, and to avoid processed meat such as ham and salami. These meats have been associated with increased risk for colon cancer (PLoS ONE, June 6, 2011).

Other factors associated with increased risk for colon cancer include: taking more than two drinks of alcohol per day, lack of exercise, being overweight, and not eating enough fruits and vegetables.


Recipe of the Week:

Golden Lentil Soup

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

June 26th, 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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