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Methionine Restriction to Prolong Life?

Humans live longer when they exercise, eat lots of fruits and vegetables, keep body fat low, and restrict excess calories, meat and protein. The latest research show that restricting a certain protein building block called methionine may be more effective in prolonging life than restricting calories or proteins.

Caloric restriction with adequate intake of nutrients prolongs life in fruit flies, roundworms, and mice by increasing insulin sensitivity and heart function, and decreasing inflammation and the muscle wasting of aging. In humans, calorie restriction helps to prevent diabetes, heart disease and cancer. However, getting all of the nutrients you need while restricting calories is very difficult.

Anything that increases cell growth and increases production of new cells in your body appears to shorten lifespan. Your cells are programmed so that when food is scarce, cells lie dormant in an attempt to conserve energy to help you survive. However, when food is plentiful, extra calories stimulate new cell growth which ultimately shortens lifespan. Researchers have identified a protein in cells called TOR (Target Of Rapamycin) which promotes cell growth. Blocking TOR increases lifespan in yeast, worms, flies and mice (Aging Cell, September 2010). Caloric restriction and a drug called rapamycin block TOR to decrease cell growth and prolong life (Nature, July 8, 2009). However, rapamycin is not safe because it suppresses immunity to increase infections and it also markedly increases blood levels of triglycerides to increase risk of heart attacks.

The most potent dietary activators of TOR are amino acids, the building blocks of protein. Restricting protein lowers TOR and another major promoter of cell growth called Insulin-like Growth Factor-1 (Rejuvenation Research, October 2007). Restricting just one amino acid, methionine, extends the life of flies and mice as much as caloric restriction does (Medical Hypotheses, February 2009). Methionine is found primarily in animal products, and is very low in foods that come from plants. Eating a diet high in fruits and vegetables and low in meat and dairy products markedly restricts intake of methionine. Furthermore, this diet is much easier to follow than one that restricts calories.

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Dear Dr. Mirkin: What pacing strategy should I use for races in hot weather?

Start out significantly slower than you usually do and gradually increase your effort to try to keep yourself from slowing down due to the heat. Eight men were asked to ride a bicycle as fast as they could for 15 minutes in 68 F. They started at a fast pace and were able to hold a steady pace. However, when they did the same time trial in 100 degree F. and started at the same pace, they slowed down progressively long before their body temperatures started to rise (Medicine & Science in Sports & Exercise, January 2010). Interestingly, their body temperatures and heart rates rose at close to the same rates in both environmental temperatures.

When you exercise, your heart has to pump blood to bring oxygen from your lungs to your muscles. Since more than 70 percent of the energy that you use to fuel your muscles is lost as heat, your heart also has to pump this extra heat from your muscles to your skin where the heat can be dissipated. When you race in hot weather, your heart works just as hard as it does in cooler weather. However, the extra work of pumping heat from your muscles to your skin limits how much blood it can pump to bring oxygen to muscles and you have to slow down.

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Dear Dr. Mirkin; Should I avoid foods that are high in cholesterol?

A review of the world's literature shows that dietary cholesterol itself is not associated with increased risk for suffering a heart attack (Current Atherosclerosis Reports, September 2010). More than 80 percent of the cholesterol in your bloodstream is made by your liver. Less than 20 percent comes from your diet. When you take in more cholesterol, your liver makes less so that your blood cholesterol remains virtually the same. The few people who do increase their blood levels of total cholesterol when they eat cholesterol-rich foods, have an increase in the good HDL cholesterol that prevents heart attacks.

Since the 1960s various organizations have recommended eating no more than 300 mg of cholesterol per day, the amount found in one egg. However, eating three eggs per day does not increase blood cholesterol levels. Poultry, eggs and shellfish, all rich sources of cholesterol, have not been shown to increase heart attack risk. Meat IS associated with increased risk for heart attacks, but I believe that the culprit is not cholesterol. A more likely explanation is the sugar-protein called Neu5GC found in meat from mammals, which may cause inflammation.

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Recipe of the Week:

Gabe's Favorite Potato Salad

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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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