Green eggs and … death?

Welcome to Impact Factor, the most scathing medical commentary on the web. I am Perry Wilson.

This week, the big egg clock has rocked again. Headlines around the world proclaim that eggs can kill you.

Today, I'm the egg, as we discuss the centerpiece of the media maelstrom – an impressive study in the Journal of the American Medical Association.^[1] In this study, the eggs are melted in the form of delicious death capsules.

It was about a year ago that I reported on a study published in Heart^[2] this suggests that increased egg consumption has been badociated with a 20% reduction in your risk of death:

"I'll say it very clearly: studies that use responses to a food frequency questionnaire to link to certain health outcomes are not worth the paper they are printed on."

Now, a study of JAMA shows the opposite. Does this justify the same brief reference? Not enough. That was about as well badyzed a nutritional epidemiology study that you can get. But keep your cap skeptical.

The researchers combined data from individual patients from six large US cohort studies. Participants provided a food history from a food frequency questionnaire initially. They were then followed for cardiovascular events and all-cause deaths for a median of 17 years.

The top results?

People who reported eating more eggs initially were more likely to have cardiovascular events in the future. They were also more likely to die from any cause.

Now, the egg eaters were a little different from the non-egg eaters.

For example, compared to individuals who do not eat eggs, those who eat two or more a day are much younger. were much more likely to be a man, a black and a current smoker; and eat twice as many calories a day.

The authors did a good job of adapting to these factors and other factors. But the negative effect of the egg remained.

Until they adjust for total cholesterol intake. After taking into account the total intake of cholesterol, the damage caused by the eggs disappeared. In simple terms, it's not the eggs that kill you, but the cholesterol in the eggs that kills you.

So, why are we talking about eggs? If the culprit is cholesterol, why did the authors articulate the study around eggs? I asked this question to the lead author, Dr. Norinna Allen.

Source: Northwest Medicine

In other words, they focused on the eggs because others focused on the eggs and they wanted to put that whole thing to bed. But was it enough to change Dr. Allen's eating habits?

"Yes, I really reduced the amount of eggs I have never eaten too much, but I also cut the amount of eggs that I feed my kids."

Should we all reduce?

There is a little information that does not make sense to me. When the authors adjusted serum cholesterol levels, the effects of egg consumption and dietary cholesterol intake remained.

The conceptual model underlying this study is as follows:

Step 1: The eggs contain cholesterol. Eating more eggs means that you eat more cholesterol. Step 2: Eating more cholesterol increases your blood cholesterol level. Step 3: Increasing cholesterol levels leads to cardiovascular disease and death.

The fact that the adjustment for cholesterol consumption eliminates the egg-death relationship confirms step 1 of this process. But adjusting for serum cholesterol should have the same effect. That's not it.

In other words, it does not seem that the bad effect of cholesterol consumption has been mediated by serum cholesterol levels. There are two possibilities here. First, there are undefined effects that require further research.

Two, this is not really the dietary cholesterol that is the problem. Perhaps the consumption of eggs and cholesterol are just indicators of another unhealthy behavior, unrelated to serum cholesterol but badociated with death.

If this is the case, it may not be justified to put more emphasis on eggs.