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Preventing Loss of Muscle Strength with Aging

As you age, you lose muscle size and strength much faster than you lose endurance or coordination. Researchers at the University of Nottingham in England show that a major cause of loss of muscle is that aging prevents muscles from responding to insulin and that exercising helps to slow this loss of muscle size and strength (The American Journal of Clinical Nutrition, September 2009).

Insulin drives amino acids into muscles to help them recover from exercise and maintain their size. Researchers traced radioactive amino acids and showed that insulin drives the amino acids into muscles much more effectively in 25-year-olds than in 60-year-olds. They also showed that the blood flow in younger people's legs is much greater and supplies far more nutrients and hormones. However, three exercise sessions per week over 20 weeks markedly increased blood flow in the legs of the older subjects, enough to reverse muscle wasting.

People of all ages can use this information to help themselves become stronger. Athletes in all sports train by stressing and recovering. They take a hard workout, damage their muscles, feel sore the next morning, and then take easy workouts until the muscles heal and the soreness goes away. The athlete who can recover the fastest can do the most intense workouts and gain the most strength.

Eating a high carbohydrate-high protein meal within half an hour after finishing a workout raises insulin levels, increases amino acid absorption into muscle and hastens recovery (Journal of Applied Physiology, May 2009). The carbohydrates cause a high rise in blood sugar that causes the pancreas to release insulin. Insulin drives the protein building blocks (amino acids) in the meal into muscle cells to hasten healing from intense workouts. Muscles are extraordinarily sensitive to insulin during exercise and for up to a half hour after finishing exercise, so the fastest way to recover is to eat protein- and carbohydrate-rich foods during the last part of your workout or within half an hour after you finish.

Here's how Diana and I (ages 67 and 74) use this information on insulin sensitivity. We ride hard and fast for about 20 miles on Tuesdays, Thursdays and Saturdays. On our recovery days, we ride slowly for one to three hours. Mid-day we go to a buffet restaurant and eat a large meal with fish, shrimp, vegetables and other sources of protein and carbohydrates. After eating, we ride slowly for one or two more hours. Riding before we eat makes our muscles very sensitive to insulin. This causes insulin to drive amino acids rapidly into our muscles and help them recover faster. Riding after we eat helps us to avoid a high rise in blood sugar that damages cells. You can use either plant or animal sources of protein; both contain all of the essential amino acids necessary for cell growth.


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Dear Dr. Mirkin: What causes prostate cancer?

We don't know, but a study from Harvard School of Public Health shows an association between the common sexually transmitted infection, Trichomonas vaginalis, and risk of the type of prostate cancer that kills (Journal of the National Cancer Institute, September 9, 2009). Researchers analyzed blood samples collected in 1982 from 673 men who were diagnosed with prostate cancer more than ten years later. Trichomonas vaginalis infection was associated with a more than triple risk for the type of prostate cancer that kills.

Trichomonas vaginalis infects about 174 million people each year and is the most common non-viral sexually transmitted infection. Up to three-quarters of men infected with Trichomonas vaginalis may have no symptoms at all. Trichomanes can usually be cured just by having all sexual contacts take metronidazole for five to ten days.

Several other cancers are caused by bacterial infections. For example, the bacterium Helicobacter pylori is the most common cause of stomach cancer. Bacteroides fragilis, a bacterium that causes diarrhea, has been associated with colon cancer (Nature Medicine, September, 2009). Chronic infections activate your immune system to cause inflammation, which can block apoptosis to cause cancer.

More than 90 percent of prostate cancers probably should not be treated because they cause no harm. A study in the Journal of the American Medical Association (September 15, 2009) followed men with early stage prostate cancer who were cared for without surgery or radiation. Ten years later, only six percent had died from prostate cancer. The average time from diagnosis to death for untreated prostate cancer is more than 22 years. However, five percent of prostate cancers may need immediate treatment as they grow rapidly and can kill. A reliable test that tells which prostate cancers are likely to kill would save anxiety, potency and continence for a lot of men. Such a test is not available at this time. The authors of this study recommend that doctors and patients reconsider the watch and wait option. More on prostate cancer


Dear Dr. Mirkin: Are low-carbohydrate diets used for weight loss safe?

A study from Harvard raises new concerns about the popular low-carb diets. Mice on a 12-week low-carbohydrate/high- protein diet had a marked increase in arteriosclerotic plaques in their hearts' arteries. They were unable to form new blood vessels in tissues deprived of blood flow, as occurs during a heart attack (Proceedings of the National Academy of Sciences, September 2009). In spite of the artery damage, blood cholesterol levels did not increase. So arteries were damaged by a low carbohydrate diet in mice, even though there was no worsening of blood cholesterol levels. Further studies are needed to see whether this occurs in humans as well.


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June 22nd, 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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