EDITORIAL May 02, 2022 May 02, 2022

Who is to blame, the chicken or the egg?

DOI: 10.20945/2359-3997000000467

While there is no more room to debate the contribution of cholesterol in the development of atherosclerotic disease, the role of cholesterol-rich foods in this outcome is much less clear. In this context, the consumption of eggs has received special attention over the years, and its critical analysis has been treated in a sophisticated, precise, and objective way by Professor Eder Quintão () in this issue of the AE&M. Consistent with this review, a recent meta-analysis of cohort studies with up to 32 years of follow-up and over 5.54 million person-years pointed to the enormous variation in the effects obtained from egg consumption. Most subjects consumed between one and less than five eggs a week. Participants with the highest egg intake had a higher body mass index, were less likely to be treated with statins and consumed more red meat. By far, the most important finding was that in a pooled multivariate analysis, consumption of at least one egg per day was not associated with cardiovascular disease (CVD) risk after adjustment for updated lifestyle and dietary factors related with egg intake. Results were similar for coronary heart disease and stroke. In line with Eder Quintão’s comment on the predominant consumption of carbohydrates in Asians, egg consumption in this population was associated with an 8% reduction in the risk of cardiovascular events. It was not possible to clarify whether egg consumption was associated with reduced carbohydrate consumption.

Assessing the effect of diets on cardiovascular risk is almost impossible due to a set of characteristics. First, foods are composed of hundreds or thousands of molecules whose actions can diverge or add up in a pathophysiologic process. Cholesterol consumption is often associated with the ingestion of saturated fat and salt, both of which can have direct cardiovascular effects. In addition to cholesterol, eggs are composed of proteins, minerals, fatty acids, phospholipids, vitamins, and carbohydrates. The most abundant phospholipid in eggs, phosphatidylcholine, contains choline, which can be converted to trimethylamine by gut bacteria. Trimethylamine is then absorbed into the circulation and modified in the liver by the flavin-containing monooxygenase to trimethylamine N-oxide (TMAO). TMAO levels are associated with cardiovascular disease risk even after adjustment for other CVD risk factors ().

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