Eggs have been in the center of the cholesterol controversy almost from the very start.
The traditional argument against eggs went that eggs, high in cholesterol (210-275 mg per egg)and with some saturated fat (1.5-2.5 grams per egg), raised blood cholesterol (and LDL). Out went the daily fried, scrambled, poached eggs that many Americans indulged in most mornings. (We replaced it with more breakfast cereals and other carbohydrate conveniences, then got enormously overweight.)
A large Harvard epidemiologic study in 1999 called this observation into question. They tracked the fate of 117,000 thousand people and then compared the rate of heart attack, death, and other cardiovascular events among various people correlated to the "dose" of eggs they ate. Egg intake varied from none to 7 or more per week. Lo and behold, people who ate more eggs appeared to not suffer more events.
This study, large and well-conducted by an internationally respected group of investigators, seem to reopen the gates for more egg consumption, though most Americans still consume eggs cautiously.
Deeper down in this study, however, was another observation: People with diabetes who ate 1 egg per day had double the risk of heart attack. Because this study was observational, no specific conclusion as to why could be drawn.
A new study conducted by a Brazilian group may shed some light. Healthy (non-diabetic) men were fed an emulsion of several eggs. Inclusion of plentiful yolks caused a dramatic slowing of fat clearance from the blood. Specifically, "chylomicron remnants" were abnormally persistent in the blood. Chylomicron remnants are potent causes of coronary plaque. (Chylomicron remnants can be measured fairly well by intermediate-density lipoprotein and VLDL by NMR, or IDL by VAP.)
Diabetics are know to have substantial disorders of after-meal fat clearance, including an excess of chylomicron remnants. Could the Brazilian observation be the explanation for the increased event rate in diabetics in the Harvard study? Interesting to speculate.
We continue to tell our patients that eating eggs in moderation is probably safe. After all, there are good things in eggs: the high protein in the egg white, lecithin in the yolk. It is the yolk's contents that are in question, not the white. Thus, you and I can eat all the egg whites (e.g., Egg Beaters) we want. It's the safety of yolks that are uncertain.
The abnormal after-eating effect suggested by the Brazilians opens up some very interesting questions and confirms that we should still be cautious in our intake of egg yolks. One yolk per day is clearly too much. What is safe? The exisitng information would suggest that, if you have diabetes, pre-diabetes, or a postprandial disorder (IDL, VLDL), you should minimize your egg yolk use, perhaps no more than 3 or so per week, preferably not all at one but spaced out to avoid the after-eating effect.
Others without postprandial disorders may safely eat more, perhaps 5 per week, but also not all at one but spaced out.
Track Your Plaque Members: Be sure to read our upcoming Special Report on Postprandial Disorders. It contains lots of info on what this important pattern is all about. Postprandial disorders are largely unexplored territory that hold great promise for tools to inhibit coronary plaque growth and drop your heart scan score. The Brazilian study is just one of many future studies that are likely to be released in future about this very fascinating area.
Hu FB, Stampfer MJ, Rimm EB, Manson JE, Ascherio A, Colditz GA, Rosner BA, Spiegelman D, Speizer FE, Sacks FM, Hennekens CH, Willett WC.A prospective study of egg consumption and risk of cardiovascular disease in men and women. JAMA 1999 Apr 21;281(15):1387-94.
Cesar TB, Oliveira MR, Mesquita CH, Maranhao RC. High cholesterol intake modifies chylomicron metabolism in normolipidemic young men. J Nutr. 2006 Apr;136(4):971-6.