Feature Article: Eggs; Hero Or Villain?

The controversy surrounding the egg is a great example of the chasm between popular opinion and current research in the field of nutrition.  Eggs have been criticized for years because of their cholesterol content.  Many doctors and even nutritionists have people throw away their egg yolks, buy egg substitutes or avoid eggs altogether in an effort to reduce their risk of heart disease and improve their health.  Well designed research regarding eggs and our health has been conducted and it’s time to set the record straight. 

Why have eggs been vilified?

Eggs are considered an unhealthy food for one basic reason; they are high in cholesterol.  A single egg has 213 milligrams of cholesterol.  The daily recommended level of dietary cholesterol is 300 milligrams per day.  So consuming one egg comes close to the daily recommendation and consuming 2 eggs at a meal exceeds the daily recommendation for cholesterol.  The theory behind the advice to avoid eggs is that consuming a lot of dietary cholesterol will raise serum cholesterol and increase risk of heart disease and stroke.

Does the cholesterol you eat in your diet increase your risk of heart disease?

Cholesterol that you consume in your diet is only weakly associated with your serum cholesterol levels.  There is strong evidence that trans fat and saturated fat consumption have a negative impact on serum cholesterol, but this does not seem to be the case with dietary cholesterol.  In both the Nurses’ Health Study and the Framingham Heart Study (2 of the largest and most well designed cohort studies in existence) dietary cholesterol was not associated with an increased risk of coronary heart disease.  (See Reference 1, Reference 2)

Have eggs been shown to increase risk of heart disease?

Several studies have examined the association between egg consumption and risk of heart disease.  In 1999, researchers from Harvard published one such study in the Journal of the American Medical Association.  They looked at egg consumption and risk of coronary heart disease in 80,082 women from the Nurses’ Health Study and 37,851 men from the Health Professional Follow-up Study (See Reference 3). Subjects were followed for 8 years and there was no evidence of increased risk of heart disease in men or women who consumed 1 egg per day.   There was, however, an increased risk in diabetic men and women who consumed 1 egg per day.  In the Framingham Heart Study, there was also no association found between egg consumption and risk of heart disease (See Reference 2).

So what else is in an egg yolk besides cholesterol?

Egg yolks are like a multivitamin supplement.  They contain vitamin D, folate, vitamin E, vitamin A, monounsaturated fats, vitamin B12, vitamin B2, essential amino acids, linoleic acid, calcium and vitamin B1.  They are, in fact, one of the most nutrient dense foods you can eat.

So what’s the take home message on eggs?

I tell my healthy clients to enjoy up to 7 yolks a week.  This amount will not have any negative impact on cardiovascular health and will absolutely pack their breakfast with essential nutrients.  The increased risk with diabetics is definitely a cause for concern.  I advise my diabetic clients to limit themselves to 3 yolks per week.  

References

1) Hu FB, Stampfer MJ, Manson JE, et al. Dietary fat intake and risk of coronary heart disease in women. The New England Journal of Medicine 1997; 337:1491-1499.

2) Dawber TR, Nickerson RJ, Brand FN, et al. Eggs, serum cholesterol and coronary heart disease. American Journal of Clinical Nutrition 1982; 36:617-25.

3) Hu FB, Stampfer MJ, Rimm EB, et al. A prospective study of egg consumption and risk of cardiovascular disease in men and women. Journal of the American Medical Association. 1999; 281:1387-94.