What does the research say about eggs?

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Well, if one took the recent CPE course made available online from the Egg Nutrition Council (ENC), one might have been persuaded that consuming eggs has little or no adverse impact on blood lipids and would be unlikely to promote atherosclerosis, heart disease, and stroke. The CPE course makes the same pseudoscientific arguments debunked by me in the September 2010 issue of Communicating Food for Health. That article was inspired by an article in the ENC’s newsletter by Dr. Fernandez. Now Dr. Fernandez at UConn has an ENCsponsored CPE course pretending to educate RDs about how eggs have been unfairly demonized as promoters of atherosclerosis. Was I wrong?

Dr. Spence examined data from 1262 consecutive Canadian men and women (mean age 61.5) who had been evaluated at a clinic for atherosclerotic plaques in their carotid arteries. At the same time of their ultrasound study, they filled out questionnaires about their diets and other CVD risk factors. In linear multiple regression analysis, egg-yolk years remained significant predictors of baseline total plaque area (TPA) after adjustment for sex, serum total cholesterol, systolic blood pressure, diabetes, BMI, and pack-years of smoking. Dr. Spence also noted that egg yolk-years were more predictive of increased atherosclerotic plaque development than either fasting cholesterol level or BMI. [Spence JD, et al. Egg yolk consumption and carotid plaque. http://www.atheroscl erosis-journal.com/article/S0021- 9150(12)00504-7/abstract]. If egg intake is of little or no concern for the development of atherosclerosis, as Dr. Fernandez’s ENC CPE course suggests, then the increase in carotid plaque with increased egg yolk intake is pretty hard to explain. It is either an amazing statistical fluke or it appears that egg yolks may indeed be promoting the growth of atherosclerotic plaque. Even worse, they appear to be doing so in ways that are at least partially independent of fasting blood lipids.

ENC’s Spin

An article written by Rod Abby and published online states "The ENC and AEB observed that subjects of the Canadian study with higher egg intakes tended to also be heavy smokers." Nice spin, but Rod Abby failed to mention that Dr. Spence’s article found this supposed “tendency” was not even close to statistically significant. Indeed, had Rod Abby read the article, he may have noticed when it stated: "There was no significant correlation between egg yolk consumption and smoking history." It appears that the ENC/AEB were attempting to spin the findings of this study to confuse the public (and perhaps some health professionals) in the same way the Tobacco Institute used to spin data from studies linking tobacco smoke with disease. Does this not suggest that commercial interests are not likely to be the most reliable sources of accurate scientific information, particularly when that data portrays what they are selling as being associated with ill health?

Actually, clinically significant atherosclerosis rarely develops when the diet is very low in fat and cholesterol. Data from the longrunning Framigham Heart Study clearly show that, over the long term, elevated serum cholesterol levels (and especially nonHDL-C level) are the single best predictor of subsequent clinically significant coronary artery disease (CAD). It is true that 80-85% of the cholesterol in the typical American's blood is made in the liver and does not come directly from the diet. However, eliminating dietary cholesterol for someone eating about 600mg/day on average will lower serum cholesterol by at least 15% on average, assuming no other change in the diet. A controlled clinical of young, healthy "vegetarians" found increasing dietary cholesterol from 97mg/d to 418mg/day with eggs only increased LDL-C by an average of 12% in just 3 weeks. [Lancet, March 1984;1:647-9]. More recently, a carefully controlled clinical trial in Brazil examined the impact of adding either 3 egg whites or 3 whole eggs daily to the NCEP Step 2 diet for 25 healthy young men (age 17-22) for 15 days. With the egg whites, dietary cholesterol averaged only 174 mg/day, but with the whole eggs, dietary cholesterol averaged 804 mg/day. As a result, the average LDL-C level was only 86 mg/dl with the egg whites but 120 mg/dl with the 3 whole eggs daily. The researchers also reported that the high cholesterol diet, in addition to raising LDL-C by 40%, also significantly impaired the removal of chylomicron remnants. [Cesar TB, et al. High cholesterol intake modifies chylomicron metabolism in normolipidemic young men. J Nutr 2006; 136: 971-6]. There is also growing data suggesting that some of the damage done to arteries from eating cholesterol-rich foods comes from alterations of postprandial blood lipids.[Spence JD, et al. Dietary cholesterol and egg yolks not for patients at risk of vascular disease. Can J Cardiol 2010 Nov; 26: e336 -9].

Bottom Line:

The evidence linking dietary cholesterol and egg consumption with higher LDL-C levels and more atherosclerotic disease will continue to be scrambled by the ENC/AEB. However, the preponderance of research shows dietary cholesterol alters blood lipids in ways that damage arteries.

By James Kenney, PhD, FACN

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