I have talked with many folks around me about Cholesterol, Saturated Fats and our diets.
I know it is confusing, but here is the skinny.
The mythologies:
1. High Cholesterol is BAD. It causes Heart Disease.
the truth? High levels of High Density Cholesterol are either good or a non-factor in atherosclerosis. Low Density Cholesterol is at worst a "marginal risk factor" for heart disease. And Very Low Density Cholesterol (or more importantly, the Lipoprotein shell that holds it) may be a bigger risk factor for Heart Disease. A 2005 study showed a 22% decreased risk of Heart Attack after 5 years of a high dosage of statin therapy (lipitor), a therapy that targets VLDL cholesterol. But VLDL is a very small portion of total cholesterol, and "total cholesterol per se is not a risk factor for Coronary Heart Disease at all". read Gary Taubes' NYTimes article for some great information on the subject.
2. Saturated Fat causes Heart disease by raising Cholesterol levels in the blood.
this ties in with the previous myth, and has much the same value, that is: not much. Saturated fat is usually well processed by the body. We have storage places for the material we cannot process if we over-eat. These places are generally not the blood, but adipose tissue. The underlaying myth here really is that saturated fats (animal fats) are harder to break down and more likely to make us FAT then poly-unsaturated fats (vegetable oils). This is not the case. But I will not belabor this point with this post. That is for another time. The important thing to note is that Cholesterol from food intake does not cause Heart Disease. (read Taubes' article for more detail)
So, what causes Atherosclerosis, and in turn Heart Disease?
Lipids (lipoproteins specifically) in the blood can and do clog up the arteries. But only if two co-factors are at work. The first is Dyslipidemia, usually a hightened level of lipids in the blood. The second is raised Intima Media Thickness, which refers to the relative thickness of arterial walls.
So, what common factor causes a rise in both Lipid levels and IMT, and as a result the risk of Heart Disease? Smoking? Fatty Foods? High Cholesterol diet?
According to this study none of these were significant factors in raised IMT levels. Meaning: Fatty foods do NOT cause higher lipid counts in the blood.
No, the common factor is Cortisol. Cortisol is a steroid produced in the adrenal cortex. In order to release cortisol into the system, the adrenals need a molecule of cholesterol. This cholesterol is produced and sent to the adrenals by the Liver.
Why is cortisol produced?
It is our most fundamental fight or flight stress chemical. When we are frightened or angry or spoiling for a fight, cortisol levels increase. The raising of Cortisol is vital to human survival, and it is healthy in small doses. What scientists have discovered is that Cortisol levels are increasingly hightened in western society, to a constant rate in many cases. This perma-fight/flight state causes increased IMT levels and Hperlipidemia (high lipids in the blood).
Some studies that show this correlation:
"How corticoids, growth hormone and oestrogens influence lipids and atherosclerosis"
So, to sum up. Stress causes Cortisol levels to rise. Cortisol in the system causes lipid levels to rise uncharacteristically, and it causes the hardening of the walls of the arteries. These two factors are the first and second factors in the Number 1 cause of death in the US: Heart Disease.
Eat and Be well.
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