Egg consumption and risk of coronary heart disease and stroke: dose-response meta-analysis of prospective cohort studies

BMJ 2013; 346 doi: (Published 7 January 2013)
Cite this as: BMJ 2013;346:e8539

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In the meta-analysis, Rong et al. concluded that egg intake was generally not related to the risk of coronary heart disease (CHD) or stroke. I have several concerns.

First, the authors stated that the study with the longest follow-up time would be selected if there were multiple publications for one study. For the Nurses’ Health Study, Bernstein et al. has updated data on egg and CHD in 2010, which should been included in the meta-analysis.

Second, in the NHANES III study, Scrafford et al reported a significant inverse association between high egg intake and stroke mortality among men (relative risk: 0.33, 95% confidence interval: 0.14 to 0.82), but a null association among women. It seems that Rong et al missed male data (refer to Fig 5 in the published meta-analysis). Would egg intake be protective against stroke after including the male result?

Further, eggs are a rich source of high quality protein and vitamins, making it biologically plausible to prevent cardiovascular disease. As addressed by Rong et al in the discussion, regular egg consumers are more likely to eat red and processed meat and other "unhealthy" food. So is it possible that the beneficial effect of egg intake, if any, was diminished by red and processed meat intake, with the fact that intake of meat, in particular processed meat has been indicated to increase the risk of CHD and stroke, and that none of the included studies in the meta-analysis controlled for meat intake?

Competing interests: None declared

Guo-Chong Chen, Student

Town, Suzhou 215123, China

School of Public Health, Soochow University, Department of Epidemiology, School of Public Health, Soochow University, 199 Renai Road, Dushu Lake Higher Education

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In India, particularly in Tamilnadu, there is a mid-day meal scheme to provide a boiled egg for five days a week. This scheme has a multi-purpose like providing enough calories to the children and also to act as an incentive for the children to attend school. This novel scheme, which started with a view to retain students to study, had its nutritious benefits. Many such school going children are poor and can ill-afford a good meal per day. For them egg consumption is to avoid malnutrition whereas for general population it is a matter of health.

The studies and analyses show that egg consumption doesn’t act as an additional risk factor for atherogenesis taking it as a rich source of dietary cholesterol. Rather it is shown to benefit the population who take eggs in the diet. The average intake of protein in certain populations is low when compared to western population. Therefore, it is better to consider egg as one of the nutrients present in a balanced diet taken by the individuals. It is always necessary to view whole body metabolism when one analyses the effect of all components of a diet to the well-being of an individual.

The methods used to rear and maintain poultry do play a role in the nutritive value of the eggs produced. Egg is a good source of cholesterol. Cholesterol is one of the essential biochemical components of cellular and metabolic function. We cannot consider or create an ambiguous feeling whether cholesterol is a friend or foe like egg is a friend or foe because of its cholesterol content.

Competing interests: None declared

dhastagir s sheriff, Professor

Faculty of Medicine, Benghazi University, Benghazi, Libya

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It is unfortunate that such a valuable and nutritious food source has been given a bad reputation on such flimsy evidence. Eggs are an excellent source of protein, calcium, vitamin D, iron, choline, selenium and several essential amino acids. The ‘diabetic’ (no type specified in the study!) population has been targeted as being most at risk of coronary heart disease and stroke from eating eggs. Unfortunately there are so many myths within diabetes management; this is yet another study which confounds the meaningful education and care which is sorely lacking in this population. I hope those diagnosed with diabetes are not prevented from ‘going to work on an egg’!

Competing interests: None declared

Jane E Collis, Independent Researcher

No affiliation, Kenilworth Warks UK

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In my opinion, the author's search strategy in this meta-analysis is very poor. Why, after countless studies demonstrating the presence of publication bias, have the authors only searched Pubmed and Embase? Is there a lack of unpublished data?

A meta-analysis by Hopewell et al (2007) showed that, on average, published studies show a 9% greater effect than unpublished studies. Thus, if authors, such as Liu et al, choose to ignore unpublished data, it should be well documented why. Ignoring the issue altogether leads to readers, such as myself, questioning the reported findings.

Competing interests: None declared

Luke Thornton, Medical Student

HYMS, Stoke-On-Trent, Staffordshire

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