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Egg Agencies Raise Doubts over Latest Health Study

21 August 2012, at 3:57pm

US - The findings of a recent study linking egg consumption to cholesterol have been questioned by the Egg Nutrition Center and American Egg Board.

The Egg Nutrition Center and American Egg Board have released a statement on recently published research on the consumption of egg and cholesterol.

Eggs have been shown to have a wide range of health benefits, providing 13 essential vitamins and minerals, high-quality protein and antioxidants, all for just 70 calories. Years of credible research has demonstrated the positive effects of the high-quality protein and nutrients in eggs on satiety, weight management, eye health and in supporting a healthy pregnancy. The journal, 'Atherosclerosis', recently published a study examining the association between the number of egg yolks consumed per week and amount of plaque in the carotid artery, a risk factor for coronary artery disease (1). The researchers concluded that regular consumption of egg yolks should be avoided by those at risk for cardiovascular disease. These findings are surprising and contradict more than 40 years of research demonstrating that healthy adults can enjoy eggs without significantly impacting their risk of heart disease.

A Harvard study with more than 100,000 subjects found no significant difference in cardiovascular disease risk between those consuming less than one egg per week and those consuming one egg per day. The researchers concluded that consumption of up to one egg per day is unlikely to have substantial overall impact on the risk of heart disease or stroke among healthy men and women (2).

Another study published in 'Risk Analysis' estimates that eating one egg per day is responsible for less than one per cent of the risk of coronary heart disease in healthy adults. Alternatively, lifestyle factors including poor diet, smoking, obesity and physical inactivity contribute to 30 to 40 per cent of heart disease risk, depending on gender (3). Additionally, research has shown that saturated fat may be more likely to raise a person's serum cholesterol than dietary cholesterol (4).

"The 2010 Dietary Guidelines for Americans recognize eggs as a nutrient-dense food that can be part of a healthful diet," says Mitch Kanter, PhD, Executive Director of the Egg Nutrition Center. "While eggs provide many nutrients and make an important contribution to overall diet quality, they are often accompanied by foods high in saturated fat and calories. These pairings were not taken into consideration in the Atherosclerosis study."

The Atherosclerosis study is an observational study that can only suggest potential relationships. The researchers imply causality between egg intake and carotid plaque but a study of this nature is not designed to measure causality. Further, the researchers did not adjust for lifestyle habits including smoking and exercise patterns, waist circumference, intake of saturated fat, alcohol, or foods commonly eaten with eggs like high-fat meats and other high-fat side dishes.

Study subjects with higher egg intakes tended to also be heavy smokers, and only a small percentage of the population consumed more than five eggs per week meaning, among other things, that the conclusions were based on a small number of subjects who actually ate more than a few eggs per week. In addition, the researchers' use of a metric called 'egg yolk years', in which subjects were asked how many eggs they have eaten per week for their entire lives and multiplied that number by the subject's age, is a calculation fraught with potential error. Lastly, although the study shows a link between egg consumption and carotid plaque area, no associations to many traditional markers of cardiovascular disease, including total serum cholesterol, LDL-cholesterol, HDL-cholesterol or body mass index (BMI) were reported. And, in fact, subjects in the highest quintile of egg-yolk years actually had the lowest levels of blood total cholesterol and LDL cholesterol.

It is important to pair eggs with other good-for-you foods, such as fruits, vegetables, low-fat dairy and whole grains as part of a balanced diet. Enjoying an egg a day can fall within current cholesterol guidelines, particularly if individuals opt for other low-cholesterol foods throughout the day.

References

  1. Spence D.J., Jenkins D.J.A. and Davignon J. 2012. Egg yolk consumption and carotid plaque. Atherosclerosis. 31 July 2012. [E-pub ahead of print]
  2. Hu F.B., Stampfer M.J., Rimm E.B. et al. 1999. A prospective study of egg consumption and risk of cardiovascular disease in men and women. JAMA. 281:1387-94.
  3. Barraj et al. 2008. A comparison of egg consumption with other modifiable coronary heart disease lifestyle risk factors: A relative risk apportionment study. Risk Analysis, published online November 2008.
  4. Harman N.L. et al. 2008. Increased dietary cholesterol does not increase plasma low density lipoprotein when accompanied by an energy-restricted diet and weight loss. European Journal of Nutrition, 47:287-293.

Further Reading

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