International Health News

Egg consumption, good or bad?

WUHAN, CHINA. Shortly after the birth of the hypothesis that dietary fat and dietary cholesterol were bad, eggs were demonized, characterized as a toxic food, and true believers took to eating only the egg white. The reason - an egg contains about 200 mg of cholesterol. This was a disaster for the egg industry since egg whites were not that popular, and also unfortunate for the general public since eggs are an inexpensive and low calorie source of important nutrients, including proteins, unsaturated fatty acids and minerals. As most readers know, it turned out that fat was not bad in the context of cardiovascular disease according to many studies up to the present, all of which seem to be ignored, and most humans can eat quit a lot of cholesterol without any impact on their blood levels.

The latest study just-published employed a meta-analysis (study of pooled, weighted studies) in order to address the association between egg consumption and the risk of coronary heart disease and stroke. The studies involved were prospective, i.e. cohort follow-up studies, and dose response was an issue. The meta-analysis included eight published studies with 17 reports (nine for heart disease and eight for stroke). They involved over 3 million person years follow-up for heart disease and 4 million person-years for stroke.

The results are simple to relate. Higher consumption of eggs (up to one per day) was not associated with increased risk of coronary heart disease or stroke. Dose response showed no increase in risk with increased consumption, although there was no data for greater than 10 eggs/week for heart disease and 7 eggs per week for stroke. Those who hold fast to the cholesterol fat is bad hypothesis will no doubt now want studies covering wider range of egg consumption, and might even point out that one egg a day meets the Americans Heart Association guidelines for cholesterol consumption. However, it must also be pointed out that many individuals can eat two or more eggs a day with no impact on their blood cholesterol levels, and the ideal study would include both 2-3 eggs per day and serum monitoring. The endpoints would have to be clinical and large cohorts needed to obtain meaningful results. It is clear that this will probably never happen.

Uffe Ravnskov, MD, PhD, describes an experiment he conducted on a sceptical Danish doctor (himself), where he measured blood cholesterol levels after eating from zero to 8 eggs per day. There was no trend at all. There are a number of similar studies which reveal that responders represent only a small percentage of random populations and that for most, the level of blood cholesterol is independent of the dietary consumption over a significant range. Therefore the results of the meta-analysis should not come as a surprise. For the small minority who experience significant cholesterol elevation with dietary consumption, we are back to the problem that serum cholesterol is a very weak risk factor in CVD evens and LDL is not involved in coronary atherosclerosis.

Rong Y, Chen L, Zhu T et al. Egg consumption and risk of coronary heart disease and stroke: dose-response meta-analysis of prospective cohort studies. BMJ 2013;346:e8539
Ravnskov U. The Cholesterol Myths. Washington: NewTrends Publishing, Inc; 2000

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