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Best Drinks for Prolonged Exercise

Drinks that contain both glucose and fructose sugars will help you race faster in competitions lasting more than a couple hours. Drinks that contain only maltodextrin, (made from starches extracted from rice, corn, potato and whole grains) are not as effective for racing because maltodextrin contains just the single sugar called glucose. However, drinks that contain maltodextrin plus fructose improve race times better than those that have maltodextrin plus glucose (Applied Physiology, Nutrition, and Metabolism, April 2012).

Therefore, make sure that your drinks contain both glucose and fructose sugars, found in fruit juices, soft drinks made with high fructose corn syrup (HFCS), and any drink made with sucrose, which is regular table sugar (Curr Opin Clin Nutr Metab Care, July 2010;13(4):452-7).

WHY RACERS NEED BOTH GLUCOSE AND FRUCTOSE: The limiting factor to how fast you can race in sports requiring great endurance is the amount of sugar that you can get into your muscles while you race. How much sugar you can get into your muscles is limited by how fast you can absorb the sugar from your intestines into your bloodstream. Sugar is transported through the intestines into the bloodstream by special carrier proteins called carbohydrate transporters. Each carbohydrate transporter is specific for each type of sugar. So if you ingest two different sugars, you use two different carbohydrate transporters and therefore can take in more sugar.

Studies show that sugar absorption into your bloodstream is increased by as much as 65 percent by taking glucose and fructose, compared to glucose alone. "The increased carbohydrate oxidation with multiple transportable carbohydrates was accompanied by increased fluid delivery and improved oxidation efficiency, and thus the likelihood of gastrointestinal distress may be diminished. Studies also demonstrated reduced fatigue and improved exercise performance with multiple transportable carbohydrates compared with a single carbohydrate." (Curr Opin Clin Nutr Metab Care, July 2010;13(4):452-7).

WHAT ARE CARBOHYDRATES? Carbohydrates are single, double, triple and more sugar molecules lined in a row. They are found in all plants and foods made from plants such as bakery products and pastas. Thousands of sugars bound together are called starch, and millions of sugars bound together so tightly that you cannot break them down are called fiber. Only single sugars can pass from your intestines into your blood stream.

When you eat starch, enzymes in your intestines knock off the end sugars, one at a time, and you absorb each sugar as it is freed from the chain. Because you lack enzymes to break down fiber, fiber cannot be absorbed from your upper intestines. However when fiber reaches your colon, bacteria there use their enzymes to split off sugar molecules from these long chains of sugars, called soluble fiber, and you can absorb sugar and short chain fatty acids through your colon. During athletic competitions, you can't wait for foods to reach your colon, so you need to take single and double sugars or starches. Taking two different type of sugars, glucose and fructose together, provides more sugar than taking just one type.

WHAT'S THE DIFFERENCE BETWEEN SUCROSE, GLUCOSE AND FRUCTOSE? Glucose and fructose are single sugars. Sucrose is a double sugar made when fructose is joined chemically to glucose.

WHY YOU NEED TO TAKE SUGARS WHEN YOU COMPETE IN SPORTS THAT LAST FOR MORE THAN TWO HOURS: Muscles use mostly carbohydrates and fats, and small amounts of proteins, to supply energy for exercise. You have an almost infinite amount of fat stored in your body, but only a very limited amount of sugar stored in your blood, liver and muscles. (Recent research shows that you also store a very limited amount of sugar in astrocyte cells in your brain, but the amount is so small that this will not protect you from bonking when blood sugar levels drop during exercise; see below).

YOU GO FASTER WHEN MUSCLES BURN MORE SUGAR: When you exercise, your muscles use mostly sugars and fat for energy. The faster and more intensely you exercise, the greater the percentage of sugar that your muscles use. The greater percentage of sugar that your muscles use, the faster you can go.

HITTING THE WALL: When your muscles run out of their stored sugar called glycogen, you HIT THE WALL and have to slow down. Your muscles hurt and you have to work harder and you move more slowly. All athletes learn, sooner or later, that they have greater endurance as long as they have sugar stored in their muscles. That means that they have to take sugar during races lasting more than an hour and a half.

RUNNING OUT OF BRAIN SUGAR (BONKING): Your brain gets almost all of its fuel from sugar in your bloodstream. When your blood sugar level drops, your brain cannot get enough fuel to function properly, you feel tired and confused and can pass out. There is only enough sugar in your bloodstream to last three minutes. To keep your blood sugar level from dropping, your liver must constantly release sugar from its cells into your bloodstream, but there is only enough sugar in your liver to last 12 hours at rest, and far less than that when you exercise. During intense exercise, your muscles draw sugar from your bloodstream at a rapid rate. Your liver can run out of its stored sugar and your blood sugar level can drop, and you bonk.

Bonking is common in bicycle races when a rider does not eat frequently, but is rare in long distance running races. When you run, your leg muscles are damaged from the constant pounding on the roads and you must slow down. However, you pedal in a smooth rotary motion which does not damage your muscles, so you can continue to pedal at a rapid cadence for many hours.

IN ALL COMPETITIONS LASTING MORE THAN TWO HOURS, YOU SHOULD TAKE SOME SOURCE OF SUGAR. When you move intensely for more than an hour or two, you run low on your muscle and liver stores of sugar. In hot weather you run out of sugar earlier than in cold weather. Almost 80 percent of the energy used to power your muscles is lost as heat. In hot weather, your heart has to work much harder, using more calories, to pump this extra heat in your blood from your muscles to your skin where the heat can be dissipated.

TRY TO AVOID OR RESTRICT SUGAR WHEN YOU ARE NOT EXERCISING. Sugars can cause very high rises in blood sugar, particularly if you do not exercise or are overweight or diabetic. Every cell in your body is like a balloon full of fluid. When blood sugar levels rise too high, sugar sticks to the outer membranes of cells. Once there, sugar can never get off. Eventually sugar is converted by a series of chemical reactions to sorbitol, which destroys the cells. This cell destruction causes all of the side effects of diabetes: blindness, deafness, heart attacks, strokes, kidney failure and so forth.

Resting muscles are inactive. They need insulin to remove sugar from your bloodstream to protect you from cell damage. However, contracting muscles actively remove sugar from the blood stream without even needing insulin. So during vigorous exercise, contracting muscles protect you from a high rise in blood sugar. The effect is maximal during vigorous exercise and for up to an hour after you finish. This benefit usually disappears completely in less than 17 hours, so you should try to restrict sugar when you are not exercising.

WHAT FOODS AND DRINKS CONTAIN GLUCOSE AND FRUCTOSE? The following foods are good sources of separate molecules of glucose and fructose, or of sucrose, which is glucose and fructose bound together:

• Fruit juices
• Most carbonated soft drinks, particularly those that contain high fructose corn syrup (HFCS)
• Fruits, including pineapple, peaches, plums, nectarines, citrus fruits such as oranges or tangerines, and so forth
• Sweet or starchy vegetables, such as peas, corn, carrots and sweet potatoes
• Nuts and seeds, such as walnuts, Brazil nuts, pecans, cashews, almonds, sunflower seeds
• Processed foods made from flour, such as cookies, crackers, chips, cereals, breads and pasta


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Everyone Should Lift Weights or Do Resistance Training

Men and women have their greatest bone density at age 30 and spend the rest of their lives losing bone. By age 60, almost all North American women, and most men, have lost so much bone that they are at increased risk for breaking their bones with minimal trauma. Today, 44 million Americans suffer from osteoporosis.

The most effective way to prevent loss of bone with aging is to lift heavy weights. Bone densities of two elite female power lifters, aged 49 and 54, who started training at age 18 and never took male hormones, were among the highest ever recorded. Their T-scores (the higher the number, the denser the bones) were up to three times high normal (Journal of Strength & Conditioning Research, March 2012; 26(3):867-872). This is amazing because 85 percent of North American women over 50 years of age suffer from either low bone mineral density or osteoporosis (U.S. Department of Health and Human Services, Bone Health and Osteoporosis: A Report of the Surgeon General, 2004).

Both of these subjects consistently lifted very heavy weights for an average of 30 years. To strengthen bones significantly, a person must lift weights consistently for a long time. All eight studies I found on competitive weight lifters and bodybuilders demonstrated significantly greater bone densities than in those who were sedentary or were non-competitive lifters.

Everybody should try to start lifting heavy weights at a young age and continue to do so for a lifetime. Otherwise, you can expect progressive weakening of your bones to the point where you will break them with minor trauma.


Eat Fish; Forget About Fish Oil Pills

Researchers from Harvard reviewed 1007 studies on fish oil pills and found 14 scientifically sound, placebo controlled, double blind studies. They concluded that taking omega-3 fatty acid pills did not reduce the risk of heart attacks, strokes, angina, heart failure, sudden heart attack death, transient ischemic attack, or all-cause mortality in patients who already had heart disease (Arch Intern Med, April 9, 2012).

On the other hand, there is very strong evidence that people who eat fish at least two times a week suffer fewer heart problems than those who do not eat fish. This may mean that by eating fish, you replace other less healthful protein sources, such as processed foods or red meat.


Recipe of the Week:

Lentil Sauce for Pasta or Whole Grains

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


April 22nd, 2012
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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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