I've been thinking a good deal about high cholesterol after reading Alberto Salazar's story about his recent heart attack. As I've posted before, staying active and staying lean are two keys for maintaining low blood cholesterol. Yet Salazar was quite active and lean. So I began to wonder if high blood cholesterol could be a separate problem from other conditions.
Usually, you see high blood cholesterol as a part of the "metabolic syndrome", a whole combination of health problems happening at the same time. Given the Western combination of inactivity and a high-saturated-fat, high-glycemic-diet, you often see people with a number of linked conditions: diabetes, insulin resistance, obesity, high cholesterol, etc. But in Salazar's case, he had high blood cholesterol without any of these other conditions (he did have high blood pressure, but this is most likely the result of the high blood cholesterol and the corresponding blocked arteries).
So how can a person who is lean and active with a relatively decent diet end up with heart disease and blocked arteries? To me, this sets up like a supply-and-demand problem between cholesterol intake/production and cholesterol absorbtion in the body.
First, does a higher dietary intake of cholesterol lead to high blood cholesterol? My vote is no. In the past, studies failed to separate out the effects of cholesterol from saturated fat in the diet. When this has been properly done, an increase in dietary cholesterol leads to a minimal increase in blood cholesterol levels. For more about this, here's a good review on this subject.
Second, radically decreasing the intake of dietary cholesterol, such as through a low-fat, low-cholesterol diet, doesn't do much to decrease blood cholesterol either. Typically with these studies, you see a sharp drop in cholesterol levels but then the body adapts in the long-term and starts to produce more cholesterol internally.
Saturated fat intake is one area that I believe can make a difference for blood cholesterol levels. This new study looks at the regular intake of cholesterol and fats in children compared to their blood cholesterol measures. Children with the lowest intake of saturated fat had an average LDL cholesterol of 95, while children with the highest saturated fat intake had an average LDL of 140. Of course, this is just one of many studies which looks at the relationship between saturated fat and blood cholesterol.
Trans fat raise blood cholesterol level and have no nutritional value. Thank goodness they are being phased out of most foods, and hopefully in the future they won't even be part of the discussion on cholesterol levels.
Given all this, reducing trans fat and saturated fat seem to be the only worthwhile options on the cholesterol intake side of the equation. The other half of this is cholesterol absorption in the body, which I will discuss in Part II.