Even though eggs are not the major contributor of cholesterol in the American diet, over the last 35 years eggs have become the visual icon of high cholesterol, both dietary and blood cholesterol, and many consumers have responded by limiting, or eliminating eggs from their diets. U.S. Department of Agriculture data show that meat, poultry and fi sh together account for nearly 45% of cholesterol intake, compared to under 36% for eggs. (1) Between 1970, when the public fi rst started hearing the diet-cholesterol message, to 1995, egg consumption decreased 24%, from 311 to 238 eggs per person per year. The message to limit dietary cholesterol had been so effective that recent surveys show that 45 to 50% of consumers considered dietary cholesterol “a serious health risk.” And since everyone seemed to replay the same nutritional messages, “less than 300 mg per day of dietary cholesterol and no more than 3 to 4 whole eggs a week,” consumers assumed that the recommendations must be not only science based but also proven safe and effective. Today as we are learning about many aspects of the more traditional conventional wisdom in nutrition, the proscriptions against eggs and dietary cholesterol are coming under increased scrutiny as new research not only questions the validity of old concepts but presents documented evidence that the old theories don’t hold up well to rigorous scrutiny.

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Today, as scientific investigation and statistical analytical methodologies have improved, research studies provide a more accurate perspective of the biological processes involved in diet-disease relationships. In fact, a 2007 observational study of 9,734 people conducted by researchers at the University of Medicine and Dentistry of New Jersey, found no increased risk for stroke, ischemic stroke or coronary heart disease when subjects ate 6 or more eggs per week. The researchers concluded that “the lack of relationship between egg consumption and cardiovascular diseases may be attributable to lack of association between serum cholesterol and egg consumption”. (2)

 

Over the years there have been numerous reports that egg consumption is not related to either plasma cholesterol levels or coronary heart disease (CHD) incidence. Epidemiological surveys across cultures, such as the Twenty Countries Study, (3) reported that dietary cholesterol and egg consumption were related to cardiovascular disease mortality using simple correlation analyses but, when multivariate analyses were included correcting for saturated fat calories, there were no relationships between CHD and either dietary cholesterol or egg intakes. Data from the Framingham Heart Study, (4), (5) the Multiple Risk Factor Intervention Trial (MRFIT) (6), the Lipid Research Clinics Prevalence Trial (7), the Alpha-Tocopheral, Beta- Carotene Cancer Prevention Study,8 the Nurses’ Health Study,8 and the Health Professionals Follow-Up Study (8) all reported that dietary cholesterol intake was not related to either plasma cholesterol levels or CHD incidence.

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In 1999 Hu and colleagues at the Harvard School of Public Health reported in the Journal of the American Medical Association (JAMA) an analysis of data from the Nurses’ Health Study and the Health Professionals Follow-Up Study on the relationships between weekly egg consumption and CHD and stroke incidences. (9) The Nurses’ Health Study included 80,082 nurses aged 34 to 59 years at study onset followed for 14 years (1980-1994) and the Health Professionals Follow-Up Study involved 37,851 males aged 40 to 75 years in 1986 and followed for 8 years (1986-1994). The investigators determined daily egg consumption from multiple food-frequency questionnaires and measured incidences of nonfatal myocardial infarction, fatal CHD, and stroke in the two study populations.

 

The investigators reported that after adjustments for age, smoking, and other potential CHD risk factors, there was no evidence for a significant relationship between egg consumption and risk of CHD or stroke in either men or women. The researchers concluded “that consumption of up to one egg per day is unlikely to have substantial overall impact on the risk of CHD or stroke among healthy men and women.” Using data from subgroup analyses, the authors noted an increased risk of CHD associated with higher egg consumption among study participants with diabetes (following an ad libitum diet) but not in those with hypercholesterolemia or excess body weight.

 

The findings by Hu et al.9 add to an ever increasing body of evidence indicating a null relationship between egg consumption and CHD risk. The fact is that most industrialized countries have reviewed the experimental and epidemiological evidence and their nutrition experts determined that dietary cholesterol restrictions are unnecessary for a heart healthy diet. (10) In addition, studies are now showing that restricting eggs from the diet can have negative nutritional effects. The protein quality of eggs is the highest value in the supermarket, and it’s available at the lowest price. Eggs have high nutrient density providing 13 different vitamins and minerals in excess of the caloric contribution. Eggs are a source of biologically available lutein and zeaxanthin which help protect eyes against age related macular degeneration, a leading cause of blindness in the elderly. In addition, eggs are an excellent source of choline, an essential nutrient needed for fetal brain and memory development and prevention of neural tube defects. And what else is there in an egg which nature has included to optimize embryonic development?: cholesterol (Should eggs be considered nature’s original “functional food”?)

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And surely, if eggs increased the risk of CHD then countries with higher per capita egg consumption should have high rates of CHD. In fact, it turns out to be just the opposite. The countries with the highest per capita egg intakes are Japan #1, then Spain and France, countries with very low rates of CHD mortality compared to the USA. As the articles in this issue of Nutrition Realities show, there are many reasons to include eggs in a healthy diet. And for segments of the population who are at nutritional risk, the elderly, growing children, low income families, and those with serious illnesses, excluding an affordable, nutrient dense source of high quality protein and a variety of essential nutrients makes very little sense and is unjust.

 

Our current understanding of the relationships between diet and CHD has moved beyond the simplistic view that dietary cholesterol equals blood cholesterol, and shifted towards an emphasis on saturated fats, obesity, and a sedentary lifestyle in CHD risk. Consider, that by giving the public one less ineffective dietary issue to concentrate on it may actually increase their awareness of some of their more risky behaviors. Slowly but surely, and with an ever expanding body of scientifi c evidence, eggs are coming back to their rightful place in the American diet. And for all those people who have been avoiding a food they enjoy, this will be a valuable shift in the conventional wisdom which will allow them to again welcome eggs back into their heart healthy diet.

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