Egg consumption and coronary artery disease risk

Featured article in the Spring 2015 Issue of Nutrition Close-Up; written by Valentine Njike, MD, MPH

Coronary artery disease (CAD) remains the leading cause of death in the United States. Well-known risk factors for CAD include hypertension, cigarette smoking, physical inactivity, and high serum cholesterol.  The prevailing view tends to be that dietary cholesterol intake leads to elevated serum cholesterol, thereby increasing heart disease risk. Evidence to support this is at best controversial. The American Heart Association (AHA) recommends that daily dietary cholesterol be limited to 300 mg/day for healthy adults and 200 mg/day for individuals with heart disease.

Eggs are the single largest source of dietary cholesterol consumed in the U.S.  Due to the cholesterol content of egg yolks (approximately 200 mg each), reduction in egg consumption had been recommended in the past in an effort to lower dietary cholesterol intake. However, there is a lack of consistent evidence to support the notion that egg ingestion leads to substantial elevation in serum lipids. It has been argued that the minimal impact of dietary cholesterol on blood cholesterol does not justify current AHA recommendations; the reduction in blood cholesterol elicited by a 100mg/day reduction in dietary cholesterol intake would result in a meager 1% decrease in mortality risk.

 

In our prior studies, daily ingestion of eggs for a period of six weeks showed no adverse effects on endothelial function (a marker of cardiovascular risk) in healthy adults or adults with hyperlipidemia. 2, 3 In our more recent study published in the American Heart Journal, we investigated the effects of eggs, Egg Beaters, or a high-carbohydrate breakfast on endothelial function in adults with clinically established coronary artery disease.4 Specifically, participants with established coronary artery disease consumed 2 eggs, ½ cup of Egg Beaters, or a high-carbohydrate breakfast daily for six weeks as part of their normal diet. The high-carbohydrate breakfast consisted of what is typically consumed in the U.S. (i.e., bagel, waffles, pancakes, or cereal and skim milk). The brands and types of high-carbohydrate breakfast products consumed were selected to provide a similar amount of calories, total carbohydrates, sugar, fiber, fat, and protein. At the end of the intervention phase, we assessed the impact of eggs, Egg Beaters, or a high-carbohydrate breakfast intake by evaluating the change in endothelial function, lipid profile, blood pressure, and body weight of the study participants.  We found that daily consumption of eggs or Egg Beaters for six weeks did not show any improvement or deterioration in endothelial function, lipid profile, blood pressure, or body weight. In comparison, daily consumption of a high-carbohydrate breakfast (excluding egg intake) for six weeks significantly increased low density lipoprotein (LDL) cholesterol among participants.

 

Thus the results of our recent study, coupled with the overall evidence in the literature, argue against the exclusion of eggs from heart-healthy diets, even among those with confirmed coronary disease. There may be net harm to overall diet quality, and health, from excluding eggs from the diet. Therefore excluding eggs from the diets of patients with coronary artery diseases, as suggested by the current AHA dietary recommendations, could potentially lead to alternate food choices that are unhealthy (e.g. foods high in starch and sugar), which are potentially associated with increased risk for cardiovascular disease morbidity and mortality. Based on our studies’ findings, routine egg intake appears to be safe and potentially beneficial for one’s health.

 

In summary, eggs are a nutrient-dense food rich in essential amino acids, and are an important source of iron, riboflavin, folate, choline, and vitamins A, B12, D, and E.  Most of these nutrients are present in the yolk portion. The preclusion of whole eggs from the diet, therefore, represents a potential reduction in overall dietary quality. Eggs represent a highly nutritious, relatively inexpensive source of amino acids, minerals, and essential fatty acids, and therefore are most likely to be beneficial to overall health.

 

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Valentine Yanchou Njike, MD, MPH is Assistant Director, Research and Evaluation, at Yale-Griffin Prevention Research Center, which is funded by the Centers for Disease Control and Prevention. Dr. Njike’s principal research interests involve methodological design, conduct, and analysis of clinical studies in chronic disease prevention.

 

Key Messages:

  • The reduction in blood cholesterol elicited by a 100mg/day reduction in dietary cholesterol intake would result in a meager 1% decrease in mortality risk.
  • Daily consumption of a high-carbohydrate breakfast (excluding egg intake) for six weeks significantly increased low density lipoprotein (LDL) cholesterol among participants.
  • Eggs are a nutrient-dense food rich in essential amino acids, and an important source of iron, riboflavin, folate, choline, and vitamins A, B12, D, and E, most of which are found in the yolk.

 

References

  1. http://circ.ahajournals.org/content/early/2013/11/11/01.cir.0000437740.48606.d1.full.pdf: Accessed 12 March 2015.
  2. Katz DL, Evans MA, Nawaz H, et al; Egg consumption and endothelial function: a randomized controlled crossover trial. Int J Cardiol. 2005 Mar 10;99(1):65-70.
  3. Njike V, Faridi Z, Dutta S, et al. Daily egg consumption in hyperlipidemic adults–effects on endothelial function and cardiovascular risk. Nutr J. 2010 Jul 2;9:28. doi: 10.1186/1475-2891-9-28.
  4. Katz DL, Gnanaraj J, Treu JA, et al. Effects of egg ingestion on endothelial function in adults with coronary artery disease: a randomized, controlled, crossover trial. Am Heart J. 2015 Jan; 169(1):162-9. doi: 10.1016/j.ahj.2014.10.001. Epub 2014 Oct 7.