Friday, December 25, 2009

Rabbits on a High-Saturated Fat Diet Without Added Cholesterol

I just saw another study that supports my previous post Animal Models of Atherosclerosis: LDL. The hypothesis is that in the absence of excessive added dietary cholesterol, saturated fat does not influence LDL or atherosclerosis in animal models, relative to other fats (although omega-6 polyunsaturated oils do lower LDL in some animal models). This appears to be consistent with what we see in humans.

In this study, they fed four groups of rabbits different diets:
  1. Regular low-fat rabbit chow
  2. Regular low-fat rabbit chow plus 0.5 g cholesterol per day
  3. High-fat diet with 30% calories as coconut oil (saturated) and no added cholesterol
  4. High-fat diet with 30% calories as sunflower oil (polyunsaturated) and no added cholesterol
LDL at 6 months was the same in groups 1, 3 and 4, but was increased more than 20-fold in group 2. It's not the fat, it's the fact that they're overloading herbivores with dietary cholesterol!

Total cholesterol was also the same between all groups except the cholesterol-fed group. TBARS, a measure of lipid oxidation in the blood, was elevated in the cholesterol and sunflower oil groups but not in the chow or coconut groups. Oxidation of blood lipids is one of the major factors in atherosclerosis, the vascular disease that narrows arteries and increases the risk of having a heart attack. Serum vitamin C was lower in the cholesterol-fed groups but not the others.

This supports the idea that saturated fat in the absence of excess dietary cholesterol does not necessarily increase LDL, and in fact in most animals it does not.

Merry Christmas!

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