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Intermittent Fasting for Weight Loss and Health

A review of the medical literature shows that intermittent fasting can lower blood sugar and fat levels, reduce high blood pressure, help people lose weight, and help to prevent and treat diabetes and heart attacks (British Journal of Diabetes and Vascular Disease, April 2013). Read more


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Why "Cool Down"?

The only known benefit of "cooling down" is to keep you from feeling dizzy or passing out after very vigorous exercise. Cooling down means that you exercise far more slowly for several minutes before you stop exercising for that session. However, cooling down does not:

• reduce next-day muscle soreness (J Hum Kinet, Dec, 2012;35:59-68),

• help you to recover faster so you can compete sooner or improve flexibility (J Hum Kinet, March 2012;31:121-9),

• improve fitness level,

• make you stronger (J Strength Cond Res, Nov, 2012;26(11):3081-8),

• prevent injuries, or

• provide any other known benefits.

Exercise-Associated Collapse

Most cases of exercise associated collapse are caused by stopping suddenly. After a long race, you should slow down gradually. Cooling down prevents feeling faint and passing out. Exercise-associated collapse is the most common reason that athletes are treated in the medical tent following an endurance event. It is caused by the loss of muscle pumping action caused by suddenly stopping exercising. On the other hand, when a person passes out during a race, it can be caused by a more serious condition that can kill a person, such as a heart attack, irregular heartbeats or heat stroke (Physician and Sportsmedicine, 2003;31(3):23-29).

Postural Hypotension

At the end of a marathon, a runner sprints over the finish line, falls down and lies unconscious for a short time. What's the most likely cause? The possibilities include dehydration, hyponatremia (excessive fluid intake with too little salt in the blood), heat stroke (a sudden uncontrolled rise in body temperature), drunkenness, a heart attack or stroke. Usually it is none of these. Almost all athletes who collapse after finishing a marathon suffer from postural hypotension: lack of blood flow to the brain because blood drops from the brain to the legs. Treatment is to lie the person on his back, raise his feet high over his head and wait for him to revive. If he or she is not alert within seconds, you should consider the more serious causes of unconsciousness and get medical help immediately.

Professors at the University of Capetown in South Africa analyzed data on runners who collapsed during an ultra-marathon (Medicine and Science in Sports and Exercise, Sept 1994;26(9):1095-1101). Most cases occurred after the runner crossed the finish line. The few cases of collapse away from the finish line were caused by diseases such as asthma and heart damage. Most cases of collapse occur in runners near the cutoff time for an award. All of the runners who collapsed had an excessive drop in blood pressure when they went from lying to standing.

Mechanism of Passing Out

During vigorous exercise, your legs drive your heart, your heart does not drive your legs. First, your leg muscles contract and squeeze the blood vessels near them to pump blood toward your heart. Then the increased amount of blood returning to your heart stretches the heart and causes it to beat faster and with more force. Then your leg muscles relax and the veins near them fill with blood to start the next cycle. When you run fast, your leg muscles do a considerable amount of the work pumping blood through your body. If you stop suddenly, the blood pools in your legs and your heart has to pick up the slack. At the end of a long race, your heart may not be able to pump more blood, so not enough reaches your brain and you end up unconscious. Cooling down will prevent this.

Cooling Down Does Not Prevent Next-Day Muscle Soreness

Some people believe that cooling down gets rid of lactic acid so that you will recover faster for your next competition or training session, but this is not true. Lactic acid build-up lasts only for a few minutes even if you do not cool down. Muscle soreness after exercise is not caused by lactic acid; it is caused by small tears in the muscle fibers.


More on TMAO and Heart Attacks

For the last two weeks I have reported on the growing interest in TMAO as a cause of heart attacks. In the latest study, Dr. Stanley Hazen at the Cleveland Clinic measured fasting blood TMAO levels in 4,007 patients who received coronary angiography to see if the blood vessels to their hearts were blocked. Three years later, those with the highest levels of TMAO had more than twice the risk of having a heart attack than those with the lowest levels (N Engl J Med, April 25, 2013; 368:1547-49).

The researchers fed lecithin to healthy human volunteers and blood levels of TMAO shot up. They gave volunteers antibiotics and blood levels of TMAO barely rose at all. This showed that bacteria in the intestines converted lecithin to TMAO. Eggs, liver, beef, and pork are the principal sources of carnitine, choline, lecithin and creatinine, the substances which can be converted by bacteria in the intestines to TMAO.

TMAO has been shown to punch holes in the inner linings of arteries of mice. When these holes start to heal, TMAO helps cholesterol attach to the damaged inner linings to form plaques. TMAO also raises cholesterol by making it more difficult for the liver and the intestines to clear cholesterol from the body.

Since Ancel Keys' groundbreaking studies in the 1940s, we have known that eating meat is associated with increased risk for heart attacks. Keys thought that the increased risk was caused by the saturated fats in meat, eggs and high-fat dairy products. However, large population studies have failed to show that saturated fats from plants (coconut, palm and palm kernal oils) increase risk for heart attacks. Therefore, many doctors no longer accept the theory that saturated fat in meat is the main cause of heart attacks. Other possible explanations for the association include:

• Inflammation (an overactive immunity) against Neu5Gc, a chemical in mammal meat and dairy products,

• Inflammation caused by infections or auto-immune diseases,

• Excess iron from meat,

• Nitrates from meat, particularly processed meats.

However, none of these theories has been widely accepted. The recent studies on TMAO offer the most promising explanation for the association between eating red meat and suffering a heart attack.

This week's medical history:
Barry Marshall, from Quack to Nobel Prize

For a complete list of my medical history biographies go to Histories and Mysteries


Recipe of the Week:

Basque Beans

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

May 5th, 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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