Based on the 116 food items in the 1984 food frequency questionnaire in NHS, we estimated that egg consumption contributed to 32% of total dietary cholesterol. Eggs also made contributions to dietary intakes of many other nutrients, including vitamin D (5%), retinol (4%), folate (4%), -tocopherol (3%), monounsaturated fat (3%), vitamin B12 (3%), vitamin B2 (3%), protein (3%), saturated fat (2.5%), linoleic acid (2%), calcium (1.3%), vitamin B1 (1.2%), and vitamin B2 (1.2%). It is conceivable that the small adverse effect of cholesterol in an egg on plasma LDL levels is counterbalanced by potential beneficial effects on HDL and triglycerides, and of other nutrients including antioxidants, folate, other B vitamins, and unsaturated fats. Since there is no single biochemical measurement that can represent the effects of various nutrients, it is important to examine the direct relationship between egg consumption and risk of CHD. Only 2 previous prospective cohort studies reported on the association between egg consumption and risk of CHD. In the Framingham Study, egg consumption was not significantly associated with either serum cholesterol or risk of CHD (RR was not provided).22 In the California Adventists Study, the RR for higher intake (3 per week) vs lowest intake (<1 per week) was 1.01.23 In a case-control study conducted in Italy,24 the RR comparing women in the upper third of egg intake with those in the lower third was 0.8.

One potential alternative explanation for the null finding is that background dietary cholesterol may be so high in the usual Western diet that adding somewhat more has little further effect on blood cholesterol. In a randomized trial, Sacks et al36 found that adding 1 egg per day to the usual diet of 17 lactovegetarians whose habitual cholesterol intake was very low (97 mg/d) significantly increased LDL cholesterol level by 12%. In our analyses, differences in non-egg cholesterol intake did not appear to be an explanation for the null association between egg consumption and risk of CHD. However, we cannot exclude the possibility that egg consumption may increase the risk among participants with very low background cholesterol intake. Also, we have limited power to examine the effect of high egg consumption (eg, 2 eggs per day). Nevertheless, the average egg consumption was 0.64 eggs per day in 1995 in the United States,50 which is well within the range of consumption in our analyses.

We found no significant association between egg consumption and risk of total stroke or its subtype. Epidemiologic studies51 have revealed no clear patterns between blood cholesterol and stroke although secondary prevention trials52, 53 showed significant reductions in stroke incidence among patients with MIs and who were treated with cholesterol-lowering drugs (statins). A recent report from the Framingham Heart Study54 indicated that intakes of total fat, saturated fat, and monounsaturated fat were associated with reduced risk of ischemic stroke, but the study did not examine the effects of dietary cholesterol or egg consumption.

In conclusion, our data suggest that consumption of up to 1 egg per day is unlikely to have substantial overall impact on the risk of cardiovascular disease among healthy men and women. The apparent increased risk of CHD associated with higher egg consumption among diabetics warrants further research.