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Why Meat-Eaters Have More Heart Attacks

Eating red meat daily is associated with a very significant increased risk for heart attacks. Now we have the strongest evidence yet to explain this association. Stanley Hazen at the Cleveland Clinic Lerner Research Institute in Ohio showed that feeding humans carnitine can increase blood levels of TMAO, a chemical that markedly increases the formation of arteriosclerotic plaques in mice arteries (Nature Medicine, published online April 7, 2013). Carnitine is a nutrient found in large amounts in red meat and in many sports drinks and supplements.

Carnitine Converted to Harmful TMAO
The new research shows the following: Red meat is the main dietary source of a nutrient called carnitine. Your intestines have huge colonies of hundreds of types of bacteria. Some of the types of bacteria in your intestines use carnitine to supply themselves with energy. They then convert the carnitine to another chemical called trimethylamine-N-oxide (TMAO). Earlier studies have shown that TMAO punches holes in the arteries of mice that start the formation of plaques in arteries.

Evidence Showing How Red Meat Forms Plaques in Arteries
• TMAO punches holes in arteries in mice.
• TMAO is formed when certain bacteria grow in the intestines and use carnitine for energy and convert it into TMAO.
• Carnitine is found in very high levels in red meat.
• People (and mice) with high blood levels of carnitine are at high risk for arteriosclerotic plaques forming in arteries.
• Blood carnitine levels rise very high after eating red meat in people who eat red meat regularly.
• Blood carnitine levels do not rise very high after vegans eat red meat.
• Certain types of bacteria convert carnitine to TMAO, the chemical that causes plaques to form in arteries.
• When humans and mice are fed red meat, their intestines become overgrown with these bacteria that make TMAO.
• Vegans (people who eat no animal products) do not form TMAO after they eat red meat. Their intestines have extremely low levels of the bacteria that convert carnitine to TMAO.
• If you feed vegetarian mice large doses of red meat, their intestines eventually overgrow with the bacteria that make TMAO.
• Mice fed large amounts of meat, have 1) large amounts of the bacteria that forms TMAO, 2) high blood levels of TMAO, and 3) increased risk for arteriosclerosis.
• Mice given antibiotics to prevent this bacterial overgrowth in the gut do not develop arteriosclerosis.

How a Plaque Forms in Arteries
First, an erosion occurs on the inner lining of an artery. Then the erosion bleeds and a clot forms. The ulcer starts to heal and only then does cholesterol deposit into the artery to start the formation of a plaque. High levels of blood cholesterol do not start the process of forming plaques; cholesterol does not form in plaques until long after arteries are damaged.

How a Heart Attack Occurs
Heart attacks are not caused by blockage of an artery by progressive narrowing of that artery. First, a plaque breaks off from the lining of the artery. Then it travels down the ever-narrowing artery until it completely blocks blood flow through that artery leading to the heart muscle. That part of the heart muscle, unable to get its usual supply of blood, suffers from lack of oxygen which causes pain and eventually death to the part of the heart muscle starved of oxygen.

We Have Not Yet Proved That Heart Attacks Can Be Prevented by Avoiding Red Meat
Over the last five years, Dr. Hazen has collected the blood of 10,000 patients at risk for heart disease. He has shown that those with high levels of TMAO are at increased risk for heart attacks (Nature Medicine. Pub Online, April 7, 2013). Other researchers have also saved blood samples from people who are vegetarians and those who are meat eaters. They will take these old blood samples and measure the level of TMAO in them. Then they can review the records of these people to confirm that the people with high levels of TMAO are the ones who suffer heart attacks, and that those with low levels are at low risk.

How to Tell If You Are at High Risk for a Heart Attack
Dr. Hazen plans to have a readily-available test for TMAO by the end of the year so that your doctor can follow blood levels of that chemical just as he or she does with blood cholesterol and CRP levels.

Sources of Carnitine
Carnitine is found in high levels in red meat and in much lower levels in fish, chicken and dairy products. Carnitine is a popular ingredient in sports supplements and protein drinks. Carnitine, itself, does not damage arteries. TMAO causes the damage.

Weight Lifters and Strength Athletes Should Not Take Carnitine
Men and women who want to become very strong often take pills and drinks containing carnitine. The new research on carnitine shows that this practice is likely to increase their risk for heart attacks.

You make muscles stronger and larger by exercising so intensely that you damage them. When they heal from the damage, muscles are stronger than before they were damaged. Athletes train by taking workouts so intense that they cause considerable muscle damage. On the next day, their muscles are extremely sore. So they take easier workouts until the soreness goes away and their muscles heal. Then when the soreness goes away, they take their next intense workout. If they can heal faster from their muscle damage, they can take their next intense workout sooner and become much stronger and better athletes.

Carnitine can help muscles heal faster, so these athletes eat steak and protein pills, and take carnitine drinks, and recover faster to be stronger athletes. Now it appears that taking large amounts of carnitine increases your chances of developing a heart attack later in life.


 

 

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Health Benefits of Running or Walking

Marathon runners Paul Williams of University of California, Berkeley and Paul Thompson of the University of Connecticut School of Medicine and Dentistry have shown that walking and running offer the same health benefits, provided that the walkers and runners expend the same amount of energy (Arteriosclerosis, Thrombosis, and Vascular Biology, published online April 2013).

The authors studied 33,060 runners in the National Runners' Health Study and 15,045 walkers in the National Walkers' Health Study. They showed that the health benefits of exercise depend on the energy you put into exercising, which is how long you exercise times how intensely you exercise (time exercising x intensity of exercise).

For the Same Benefits, Walking Requires More Time and Distance

Time: Since runners usually run far more intensely than walkers walk, it usually takes walkers twice as long to expend the same amount of energy as runners. That means that an hour of walking usually gives you the same health benefits that you get from half an hour of running.

Distance: A person needs to walk more than four miles at a brisk pace to use the same amount of energy it takes to run three miles.

Health Benefits

The authors measured the exercisers' blood pressure, blood sugar and cholesterol at the beginning of the study and then followed them for 6.2 years to see who developed high blood pressure, high cholesterol, heart attacks or diabetes. The runners were 38 percent less likely to develop high blood pressure, 36 percent less likely to have high cholesterol and 71 percent less likely to develop diabetes than the walkers. However, when corrected for the amount of energy used, walking and running were statistically about the same.

Walking is Safer than Running

Runners are injured far more frequently than walkers. Your susceptibility to injury is proportional to how hard your foot hits the ground. The force of your foot strike is transmitted up your leg to your back. The harder you hit the ground, the greater the potential to damage your joints, bones, ligaments, muscles and back.

When you walk, you always keep at least one foot on the ground. Therefore, the force of your foot strike rarely exceeds your body weight. On the other hand, when you run, both feet are off the ground at the same time. That means that the faster you run, the greater the force of your foot striking the ground. When you run at six-minute mile pace, your foot strike force equals three times your body weight.

My Recommendations

I believe that everyone should follow an exercise program that causes you to use at least the amount of energy of one hour of walking or half an hour of running, every day. For maximum benefit, follow my Principles of Training.


This week's medical history:
C.W. Post, Entrepreneur

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


Recipe of the Week:

Turkish Three-Bean Soup

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




April 14th, 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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