At the beginning of my 30-year medical career, egg consumption was condemned as a cause of heart attacks. Heart attacks can kill. How did eggs kill? It was thought to be related to the cholesterol content – 200 mg per egg – leading to higher serum cholesterol levels, which clogged arteries (atherosclerosis), leading to heart attacks.
Fifteen years ago the pendulum began to swing the other direction: Egg consumption didn’t seem to matter much, if at all.
The evidence is usually collected in observational, epidemiologic studies of large groups of people. The groups are analyzed in terms of overall health, food intake (e.g., how many eggs per week), healthy lifestyle factors, etc. Egg consumption of the group is broken down, for example, into those who never eat eggs, eat 1-4 eggs per week, eat 5-10 per week, or over 10 eggs weekly. A group is followed and re-analyzed over 10-20 years and rates various diseases and causes of death are recorded. Researchers don’t follow just 25 people like this over time. You need thousands of participants to find statistically significant differences.
The debate about eggs was re-opened (although never really closed) by the publication in April, 2008, of an article in The American Journal of Clinical Nutrition. Scientists of the Physicians’ Health Study suggest that consumption of seven or more eggs weekly is associated with significantly increased risk, over 20 years, of all-cause mortality. Interestingly, this level of consumption did not cause heart attacks or strokes. Study participants, by the way, were 21,327 Harvard-educated male physicians. 5,169 deaths occurred during 20 years of follow-up. If you’re not a Harvard-educated male physician, the study results may not apply to you.
When physicians with diabetes – type 2’s mostly, I assume – were analyzed separately, consumption of even less than seven eggs per week was associated with higher all-cause mortality.
Several other observational studies looking at this same issue have found no association between egg consumption and cardiovascular disease, heart attacks, and all-cause mortality.
Bottom line? If you worry about egg consumption, limit to 7 or less per week. If you have type 2 diabetes, consider limiting to 4 or less per week.
I wouldn’t be surprised if a study were published next week saying “eat as many eggs as you want; they don’t have adverse health effects.”
Remember, all the cholesterol is in the yolk. Try making an omelet using the whites only. But in our lifetimes you’ll never see an observational study looking at egg white consumption and mortality rates.
I’m still not convinced egg consumption is worth losing sleep over. “More studies are needed…”
Steve Parker, M.D.References:
Nakamura, Y., et al. Egg consumption, serum cholestrol, and cause-specific and all-cause mortality: the National Integrated Project for Prospective Observation of Non-communicable Disease and Its Trends in the Aged, 1980. American Journal of Clinical Nutrition, 80 (2004): 58-63.