After years of bad publicity, the jury is still out on eggs. Nobody really knows whether they increase risk for heart attacks. Most of the research papers show that those who have normal blood pressure and cholesterol and are not diabetic are not at increased risk for heart attacks when they eat up to one egg a day (JAMA, 1999; 281:1387-94; Curr Opin Clin Nutr Metab Care, 2006; 9:8-12).
However, there are dissenting studies: * Canadians who ate three egg yolks a week suffered increased rate of heart attacks (Atherosclerosis, August 2012). * Australian Aborigines who ate more than two eggs per week had almost triple the rate of heart attacks compared to those who did not eat eggs (Preventive Medicine 2007;44(2):135-42). * People in the United Kingdom who consumed six or more eggs per week had an almost triple increase in rate of death from heart attacks (Heart 1997;78(5):450-5).
Is Lecithin the Culprit? Recent research from the Cleveland Clinic shows that eggs may increase heart attack risk by a mechanism that has nothing to do with cholesterol. Lecithin, found in large amounts in eggs yolks, appears to increase heart attack risk. Bacteria in the intestines convert lecithin to TMAO, a chemical that has been shown repeatedly to damage the inner linings of arteries to start plaques forming in arteries and increase heart attack risk (NEJM, April 25, 2013;368:1575-1584). The same bacteria convert carnitine in meat to TMAO that also increases heart attack risk. Some intestinal bacteria can convert lecithin, carnitine, choline and creatinine to TMAO.
Egg Yolks and Cholesterol Egg yolks are one of the most concentrated food sources of cholesterol. Eating more than one egg a day can raise blood cholesterol levels a very small amount for some people. However, most of the recent research shows that dietary cholesterol is probably not a significant risk factor for heart attacks. More than 80 percent of the cholesterol in your body is made by your liver. When you eat less cholesterol, your liver makes more. When you eat more cholesterol, your liver makes less.
Limit Eggs if You Have High Cholesterol or High Blood Pressure or are Diabetic Eggs may increase risk for heart attacks for those who are diabetic or have high cholesterol or high blood pressure. There is data to show that eating more than one egg a day increases heart failure risk for these people (Circulation, 2008; 117:512-6).
The Framingham Heart Study found no association between eating eggs and heart attacks. The Health Professionals Follow-up Study and the Nurses' Health Study found no association between an egg a day and heart attacks, but excluded people who smoked, had high cholesterol, heart attacks, diabetes, or cancer (The Journal of the American Medical Association 1999;281(15):1387-94). Excluding these risk factors removes the people most likely to suffer heart attacks from eating eggs. However, male physicians who ate more than six eggs per week did have an increased rate of heart attacks (The American Journal of Clinical Nutrition 2008;87(4):964-9). So did Englishmen consuming more than six eggs per week (Heart 1997;78(5):450-5).
My Recommendations: Eating three eggs a week appears to have no effect on risk for heart attacks. I recommend no more than one egg per day, but we do not really know what amount is safe. Almost everyone needs to limit the foods that are often eaten with eggs: sausage, bacon, fried potatoes, cheese, bakery products and so forth.
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