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Why You Should Eat Sugar During Prolonged Exercise

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. Since sugar requires less oxygen than fat and protein do, keeping sugar in your muscles as a fuel for exercise reduces your needs for oxygen and helps you to exercise faster and with more intensity in endurance events. You can markedly improve performance in endurance sports by eating jut before your event begins, and starting to eat and drink soon after you start exercising.

During exercise, muscles draw sugar rapidly from your bloodstream. 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. However, there is only enough sugar in your bloodstream to last three minutes at rest. To maintain blood sugar levels, your liver has to release sugar into your bloodstream. But there is only enough sugar in your liver 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 Depend on Hunger
Hunger during exercise is a very late sign of not getting enough calories. You can increase endurance by starting to eat anything or to drink fluids that contain sugar as soon as you start to exercise. This will give you far greater endurance than waiting to take food after an hour of exercise or when you feel hungry.

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.

Sugar and Caffeine
Sugared drinks are absorbed faster than sugared foods, and caffeine increases the rate of absorption of sugars by up to 25 percent. Higher doses of caffeine are not more effective than the low doses found in a cup of coffee or a couple of soft drinks, so athletes often take sugared, caffeinated soft drinks such as Coca Cola or Pepsi. Very high doses of caffeine can cause irregular heart beats and kill you, so you should never take caffeine pills. During a competition you should try to limit your intake of caffeine to not more than the equivalent of three cups of coffee or nine cups of soft drinks (one cup of coffee usually contains the same amount of caffeine as three soft drinks or two cups of tea).

In Events Lasting More than Two Hours, Eat Food
In very long events, you cannot get enough calories from drinks. You have to eat solid food. Good sugar-containing foods include sugared whole grain bars or almost any type of sandwich.

Eating Before Competing
Before competions, knowledgeable competitive athletes cut back on their training load and eat a little more of foods that contain carbohydrates. This increases the amount of sugar stored in their muscles at the start of their event, but it is far less important than what they do during their event.

Avoid Sugar When You Are Not Exercising
A high rise in blood sugar causes sugar to stick to the outer surface of cell membranes. Once there, sugar can never get off and is eventually converted by a series of chemical reactions to sorbitol which destroys the cell and can damage every cell in your body. All of the horrible side effects of diabetes are caused by sugar sticking to cells. You do not have to be diabetic to suffer nerve, brain and blood vessel damage from a high rise in blood sugar. Therefore what is good for you during exercise can harm you at rest.

Contracting muscles can draw sugar from muscles without requiring insulin, but . resting muscles cannot. Therefore, during exercise, a high sugar intake is usually harmless, but when muscles are not contracting, blood sugar levels can rise very high and damage every cell in your body.

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Dear Dr. Mirkin: Should we take potassium iodide to protect ourselves from the earthquake-damaged nuclear power plants in Japan?

No; it is highly unlikely that radioactive iodine from Japan will reach anyone outside of that country. However, let me explain why potassium iodide is given to people who might be exposed. All radioactivity from radioactive iodine ends up in the thyroid gland because all retained iodine taken into the body ends up in the thyroid. That means that radioactive iodine causes a very high rate of thyroid cancer, particularly in children. Taking a large dose of safe iodine before exposure to radioactive iodine saturates the thyroid gland with iodine so no more iodine can get into it.

Where exposure is a concern, adults are advised to take a 130 mg pill of potassium iodide and children, 65 mg. This saturates the thyroid gland for 24 hours. If the exposure to radioactive iodine continues, they will recommend a second dose 24 hours later. However, taking this dose every day for many weeks can cause the thyroid to be overactive which can weaken bones and cause irregular heart beats. In 2002, the US Congress legislated that the government should supply potassium iodide pills to people living within 20 miles of nuclear power plants, but this has never been done.

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Dear Dr. Mirkin: Why do you say that people should eat "huge" amounts of fruits and vegetables?

A review of 50 published studies covering 500,000 people shows that the fruit and vegetable-based Mediterranean diet is associated with reduced risk for high blood pressure, blood sugar, triglycerides, cholesterol and abdominal obesity; all major risk factors for heart attacks, strokes, diabetes, and certain cancers. It also raises blood levels of the heart-attack preventing good HDL cholesterol (Journal of the American College of Cardiology, March 15, 2011). Abnormal blood pressure is defined as above 120/80; fasting blood sugar as higher than 100 mg/dL; abdominal obesity as 35 or more inches for women and 40 inches or more in men; levels of the good HDL cholesterol as under 40 in men and under 50 in women, and triglycerides as higher than 150 mg/dL.

The Mediterranean diet also contains whole grains, low-fat dairy products, weekly consumption of fish, poultry, nuts and legumes; and monounsaturated fatty acids such as olive oil. Red meat, sugared foods and drinks, and processed foods are restricted.

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Recipe of the Week:

Sweet Potato Curry

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March 20th, 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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