cardiovascular

You are all no doubt acquainted with the popular hypothesis on cholesterol and heart disease. It has two parts: first, that eating cholesterol in the diet raises cholesterol levels in the blood; and two, that high cholesterol levels in the blood cause heart disease.

You might be surprised to learn that neither of these statements is true. The first one is relatively easy to dispatch. In the Framingham Heart Study, which is the longest-running and perhaps most significant study on heart disease done to date, it was demonstrated that intake of cholesterol in the diet had absolutely no correlation with heart disease. If you look at the graph below, you’ll see that both men and women with above average intake of cholesterol had nearly identical rates of heart disease as men and women with below average intake of cholesterol.

In fact, the “diet-heart hypothesis”, which is the scientific name for the idea that eating cholesterol causes heart disease, has even been discounted by the researchers who were responsible for its genesis. Ancel Keys, who in many ways can be considered the “father” of the cholesterol-heart disease hypothesis, had this to say in 1997:

This is a reference to early studies performed on chickens and rabbits where they force-fed these animals high-levels of cholesterol. Since rabbits and chickens are mostly vegetarian, their physiology is not adapted for processing such large amounts of dietary cholesterol, so it’s no surprise they developed atherosclerosis. The mistake was assuming that the results of this experiment could be extrapolated to humans, who are omnivores with significant differences in physiology.

The second tenet of the cholesterol-heart disease hypothesis, the notion that high cholesterol levels in the blood cause heart disease, is referred to as the “lipid hypothesis” in the scientific community. Though it still accepted as gospel truth by the general public and many medical professionals, most researchers now believe the primary causes of heart disease are inflammation and oxidative stress. Unfortunately, the rest of us haven’t gotten the memo, so to speak, that cholesterol isn’t the cause of heart disease.

It would take several articles to explain this in complete detail, but I’d like to give at least a brief summary here.

If cholesterol caused heart disease, it should be a risk factor in 1) all ages, 2) both sexes and 3) all populations around the world (barring any protective factor, of course). Also, if cholesterol caused heart disease we would expect that lowering cholesterol would reduce heart disease. But none of these assumptions turn out to be true.

The rate of heart disease in 65-year old men is ten times that of 45-year old men. Yet a recent study in the Journal of American Medical Association indicated that high LDL cholesterol is not a risk factor for from coronary heart disease (CHD) mortality or total mortality (death from any cause). It is extremely unlikely that a risk factor for a disease would stop being a risk factor at a time when that disease kills the greatest number of people. That is akin to suggesting that smoking causes lung cancer in young men, but somehow stops doing so in older men!

Another consistent thorn in the side of supporters of the “lipid hypothesis” is that women suffer 300% less heart disease than men, in spite of having higher average cholesterol levels. At the recent Conference on Low Blood Cholesterol, which reviewed 11 major studies including 125,000 women, it was determined that there was absolutely no relationship between total cholesterol levels and mortality from cardiovascular or any other causes.

Nor is cholesterol a risk factor in all populations around the world. In fact, some of the populations with the highest levels of blood cholesterol have among the lowest rates of heart disease, and vice versa. Dr. Malcom Kendrick, a well-known skeptic of the lipid-hypothesis, explains this very well in the video below:

Finally, more than 40 trials have been performed to determine whether lowering cholesterol levels can prevent heart disease. In some trials heart disease rates went down, in others they went up. But when the results of all of the trials were taken together, just as many people died in the treatment groups (who had their cholesterol levels lowered by drugs) as in the control groups (who had no treatment).

If you’re still skeptical after reading all of this, perhaps William Castelli, the director of the famed Framingham Heart Study mentioned above can convince you:

Or how about Frederick Stare, a long-time American Heart Association member and (former) proponent of the lipid hypothesis:

So there you have it. Contrary to popular belief, cholesterol is not a dangerous poison that causes heart disease. Rather, it is an essential nutrient present in the cell membranes of all tissues of all mammals, and has some very important functions in the body. In fact, in many studies low cholesterol has been associated with an increase in total mortality!

Again, the Framingham Study which followed 15,000 participants over three generations:

In other words, as cholesterol fell death rates went up.

The Honolulu Heart Program study, with 8,000 participants, published in 2001:

And finally, the huge Japanese Lipid Intervention Trial with over 47,000 participants:

In other words, those with the lowest cholesterol had the highest death rate, and those with cholesterol levels that would today be called “dangerous” had the lowest death rate.

As you can see, not only does high cholesterol not cause heart disease, low cholesterol can actually be dangerous to your health. So toss out your vegetable oil and start eating butter and eggs again! But more on that next week…

Recommended links

• Handouts from my recent public talk on cholesterol
• Dr. Uffe Ravnskov’s “The Cholesterol Myths”
• The International Network of Cholesterol Skeptics