Researchers followed 27,078 Finnish men for 31 years and found that the more dietary cholesterol and eggs a person ate, the greater the premature total death rate and death from heart attacks (Circulation, April 1, 2022;145). They reviewed 41 other prospective studies and found the same association between dietary egg and cholesterol intake and increased total and heart attack death rates. These results are similar to those of the NIH-AARP Diet and Health Study that followed 521,120 U.S. adults, average age 62.2 years, for an average of 16 years and found that eating half an egg per day was associated with increased risk for death from heart attacks, cancer, and all causes (PLoS Med, Feb 9, 2021;18(2):e1003508). Each egg yolk contains approximately 200 mg of cholesterol, and each additional 300 mg of dietary cholesterol eaten daily increased risk for death from all causes by 19 percent, heart attacks by 16 percent and cancer by 24 percent. A previous study found similar results (JAMA, 2019;321(11):1081–95).
However, a review of 40 studies published between 1979 and 2013 found some controversy about harm from eating eggs (Am J Clin Nutr, 2015;102(2):276–94). Researchers analyzed 211 different papers and found that more than 85 percent reported that eating eggs raised blood cholesterol (American J of Lifestyle Med, Dec 11, 2019), but there is enough controversy about whether dietary cholesterol is harmful that the American Heart Association and American College of Cardiology (2013) and the U.S. Dietary Guidelines (2015-2020) did not mention lowering dietary cholesterol as a strategy to help prevent heart attacks. I do not know if this oversight is due to industry pressures.
TMAO, Rather than Cholesterol, May Be the Culprit
For many years, researchers have suggested that preventing heart attacks involves restricting egg yolks and all other foods that are rich in cholesterol, but there is now extensive evidence that egg yolks may increase heart attack risk by a different mechanism. Egg yolks contain lecithin and choline, two chemicals that are converted by some of the bacteria in your colon into a chemical called TriMethylAmine (TMA). TMA is absorbed into your bloodstream and travels to your liver where it is converted to TriMethylAmine Oxide (TMAO). TMAO can damage blood vessels to start plaques forming in your arteries, can increase clotting that causes heart attacks and strokes (Cell, March 24, 2016;165(1):111–124), and can damage DNA in your cells to increase cancer risk. A review of 17 clinical studies covering 26,167 subjects, followed for an average 4.3 years, found that high blood levels of TMAO are associated with almost double the increased risk for an early death (European Heart Journal, July 19, 2017;38(39):2948–2956). The chances for dying increased by 7.6 percent for each 10 micromoles/L increase in blood levels of TMAO. Lowering blood levels of TMAO helps to prevent heart attacks (Cell, Dec 17, 2015;163(7):1585-95).
Comparing Eggs to Other Breakfast Foods
Sugar and other refined carbohydrates may put you at higher risk for heart attacks, diabetes and premature death than getting cholesterol and TMAO from meat and eggs. It makes no sense to replace eggs with:
• pancakes, waffles or French toast covered with sugary syrup
• many dry breakfast cereals that are made by grinding whole grains into flour, removing most of the fiber and adding sugar
• bakery products such as bagels and muffins
• sausages, bacon and other processed meats that can increase risk for cancers as well as heart attacks
Your overall diet is far more important than whether or not you eat eggs on occasion (Nutrients, 2015 Sep 3;7(9):7399-420). I believe that most North Americans should restrict eggs to not more than three or four a week, and they should not be eaten with red or processed meats (JAMA, 1999;281:1387-94). If your LDL cholesterol is over 100, or you have heart problems or diabetes, I think that you should avoid eating eggs (Am J Clin Nutr, 2013;98:146-59). A more healthful breakfast can contain oatmeal or other whole grains, with nuts and fruits added for flavoring. Nuts are not fattening, even though they contain lots of fat, and fruits contain healthful soluble fiber.