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Recovering from Strenuous Exercise

Milk, all sugared soft drinks, and fruit juices all help athletes to recover from endurance exercise (Medicine & Science in Sports & Exercise, October 2011). This study shows that two sugars, galactose in milk and fructose in soft drinks and fruit juice, may be the best sugars to replace sugar stored in liver. When you compete in endurance sports, sugar stored in muscles prevents HITTING THE WALL, and sugar stored in your liver prevents BONKING. Glucose, the sugar that circulates in your body, is far less effective in replacing stored sugar in liver.

HOW YOUR BODY HANDLES THE DIFFERENT SUGARS: Carbohydrates are sugars, either alone, or bound together in doubles, triples, up to long chains of sugars. Fruit juices contain fructose and glucose bound together. Sugared soft drinks contain glucose and fructose, separately. Milk contains glucose and galactose bound together.

Only single sugars can be absorbed from your intestines. Of all sugars, only four (glucose, fructose, galactose and mannose) can pass into your bloodstream. Glucose is the only sugar allowed to circulate in your body. Fructose and galactose are immediately taken up by your liver and are stored as sugar in your liver. When liver sugar stores are full, almost all fructose is converted to fat called triglycerides.

OXYGEN LIMITS HOW FAST YOU CAN MOVE. The limiting factor to how fast you can move in sports that require endurance is the time it takes to move oxygen into muscles. Anything that reduces your need for oxygen or increases your oxygen supply will allow you to move faster in endurance events.

HOW SUGAR MAKES YOU A BETTER ATHLETE. Sugar requires less oxygen to power your muscles than fat and protein do, so anything that helps you burn more sugar or supplies you with more sugar will give you more speed in events requiring endurance.

YOU STORE SUGAR ONLY IN YOUR MUSCLES AND LIVER. Your body can store only a limited amount of sugar in your muscles, liver and blood. Sugar cannot be stored anywhere else. On the other hand, you can store an almost unlimited amount of fat.

BONKING: Your brain gets almost 100 percent of its energy from sugar in your bloodstream. Your bloodstream contains only enough sugar to last three minutes, so your liver has to release its stored sugar to maintain blood sugar levels. However, there is only enough sugar stored in your liver to last up to 12 hours at rest, less during exercise. When blood sugar levels drop, you "bonk": your brain suffers from lack of its energy source, you feel weak and can even pass out. So you have to keep on taking sugar during prolonged exercise or store more sugar in your liver.

Your liver can convert certain protein building blocks called branched chain amino acids into sugar to be used by your body, and your liver can release its stored sugar, but the most effective way to prevent bonking is to take carbohydrates (sugars) during exercise.

HITTING THE WALL: Your muscles require less oxygen when they use sugar for fuel. Your muscles get sugar to be used for energy from your bloodstream, and from stored sugar in muscles. When your muscles run out of their stored sugar and you do not take sugar constantly, you "hit the wall": you lose power, your muscles hurt and you have to slow down.

CARBOHYDRATE LOADING: Many years ago, athletes were told to eat lots of extra carbohydrates before athletic competitions requiring endurance. Scientists no longer recommend this. All fit athletes need do to store maximal amounts of sugar in their livers and muscles is to cut back on their workloads a few days before competition and eat a little extra carbohydrates. Once your muscles fill with their stored sugar supply, all the extra sugar from carbohydrates you take in is converted to fat which slows you down.

IN SPORTS EVENTS REQUIRING ENDURANCE, IT IS MORE IMPORTANT TO TAKE SUGAR DURING COMPETITION. When you take sugar and you are not exercising, the sugar first fills up your sugar stored in your liver and muscles. Then all extra sugar is converted to fat that is stored in your body. Extra fat in muscles causes your muscles to use more fat and less sugar which can slow you down when you compete in sports. On the other hand, when you take sugar during competition, your contracting muscles remove the sugar from your bloodstream and use it for energy long before you store any extra fat.

YOU RECOVER FROM COMPETITION FASTER WITH MILK OR SUGARED DRINKS. Galactose in milk and fructose in fruit juice and soft drinks replace stored liver sugar more than twice as fast as the single sugar, glucose. However, avoid sugared drinks when you are not exercising, since your muscles will not remove sugar as fast as when they were being exercised and blood sugar levels can rise too high, which can cause sugar to stick to the surface of cell membranes which can damage every cell in your body.

SUMMING UP: You will have greater endurance if you take any source of sugar during competitions. You will recover faster from intense exercise by taking sources of fructose (fruit, table sugar, High Fructose Corn Syrup) or galactose (milk) during and within one hour of finishing an endurance event. You should not take sugar at other times.


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Exercise Capacity Predicts Time of Illness and Death

Rats who had greater endurance shown by their genetic ability to run longer on a treadmill lived 24 to 48 percent longer than those who have less endurance on a treadmill (Circulation Research, Epub September 15, 2011). Rats were bred so that some had great endurance on a treadmill while others had very little. The genetic markers for endurance also predicted longevity. Those with the highest ability to take in and use oxygen (VO2Max) lived the longest.

As the rats aged, those with poor endurance had more evidence of heart damage (weaker heart muscles, higher blood pressure, and less ability to transport calcium inside heart muscle cells). They also were far less active and weighed more. Low aerobic exercise capacity is a strong predictor of premature illness and death in healthy adults and in those with heart disease. In older people, poor performance on a treadmill predicts increased risk for illness and death.

Genetic ability to run or cycle long distances will help you live longer, but you can also help yourself live longer by exercising every day to increase your endurance. If you are not exercising continuously every day, you are shortening your potential life span.


Trans Fatty Acids Are Harmful

Trans fatty acids are found in partially hydrogenated oils that are added to prepared foods to give them a longer shelf life, and to make fried or baked foods more crispy. Trans fats have been associated with increased risk for cancers of the colon, breast, prostate and pancreas (European Journal of Cancer Prevention, November 2011). They raise the bad LDL cholesterol and lower the good HDL cholesterol, and have been associated with increased risk for heart attacks and premature death. The U.S. Government has legislated that all foods that contain trans fats have their presence stated on the label. They will probably soon be gone from our food supply, but meanwhile everyone should read the labels on every prepared food and avoid buying foods that contain trans fats.


Recipe of the Week:

Firehouse Chili

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October 9th, 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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