HEALTH WATCH: Assessing egg risk factors

By Michael Greger, M.D.

HOW ELSE can we make decisions for ourselves and our families but by the best available balance of evidence? The latest meta-analysis, pooling data from more than a dozen studies involving more than 300,000 people, indicates that there is a dose dependent association between egg consumption and the risk of cardiovascular disease and diabetes.

But that doesn’t mean every individual study showed evidence of harm. Even though the totality of evidence points to harm, the egg industry can cherry-pick studies that show no apparent effects.

If eggs are harmful, why don’t all of the studies on heart disease and egg consumption show significant harm? It may have to do with Geoffrey Rose’s “sick population” concept. If an entire population is sick, then the range of “health” may not be sufficiently broad to establish a significant association. Rose’s paper is one of the most famous papers ever written in preventive medicine and should be required reading for all medical students.

Imagine if everyone smoked 20 cigarettes a day. If everybody smoked, then clinical studies, case-control studies, and cohort studies would all lead us to conclude that lung cancer was a genetic disease; and in one sense that would be true. Some smokers get cancer; others lifelong smokers never do.

But if everybody smoked, we’d never know that smoking was a risk factor. Thankfully, in the case of cigarettes and lung cancer, it so happened that the original study populations contained about equal numbers of smokers and non-smokers. In such a situation, studies are able to identify smoking as the main risk factor.

But take cholesterol. In the famous Framingham Heart Study. There’s hardly any difference because practically everybody’s cholesterol was too high; it’s like everyone was a smoker. The painful truth is that even someone at “low risk” for heart disease is likely to die of heart disease. Everyone who eats the standard Western diet is, in fact, a high-risk individual when it comes to heart disease.

In a sick population like ours where nearly everyone is eating lots of saturated fat and cholesterol, adding some more saturated fat and cholesterol in the form of eggs may just take us from one sorry state—probably dying from heart disease—to another sorry state—still probably dying from heart disease.

So when the current US federal guidelines say we need to particularly restrict dietary cholesterol if we’re at high risk for heart disease, we need to realize that nearly all Americans that live past middle age are at high risk of dying from heart disease—it’s our #1 cause of death. As stroke specialist David Spence and colleagues put it, “A 20-year old man might feel safe smoking and eating egg yolks because his heart attack is 45 years or so in the future. But why would he want to accelerate the progression of his atherosclerotic plaque and bring it on sooner? Stopping egg yolks after the heart attack would be like quitting smoking after lung cancer is diagnosed.”

There may in fact be a plateau of risk for smoking, too. Whether we smoke for 25 years or 35 years, our risk for lung cancer may be the same—really high, but about the same. The tobacco industry could truthfully tell someone who’s smoked for most of their lives that, don’t worry, you can keep smoking and your risk of lung cancer won’t go up (conveniently failing to mention that if you’re already at high risk and you quit completely, your risk would drop dramatically). It’s like if you took a raging drunk and had them take a shot of whiskey. In someone who’s hammered, it might not make much difference, but to a teetotaler, a couple shots could have quite an effect. So it’s like the alcohol industry with a group of drunks saying, see, couple shots, no big deal. But that doesn’t mean it’s not better to be sober.

Instead of going from high risk to high risk, better to go to low risk or no risk.