Saturated fat and the C57BL/6 mouse

You may have seen the reports from a number of sources detailing how scientists have discovered why a diet rich in saturated fats is harmful or that scientists have figured out the “science” of saturated fats. Don’t worry about the harmful part unless you happen to be a C57BL/6 mouse or even an apoE-/- mouse. If you’re a human, however, I wouldn’t lose any sleep over it.
All these reports come from an advanced online publication from the Journal of Clinical Investigation showing that the above referenced mice tend to take up more saturated fat and show greater signs of atherosclerosis when fed a diet high in saturated fat and cholesterol than they do when consuming a standard chow diet. Problem is we don’t know from the study whether the two diets contained the same number of calories or not, which would be pretty important to know. Another problem is that the amount of cholesterol fed the mice is enormous by human standards, and—and this is a big and—we don’t know if the cholesterol is oxidized or not. Cholesterol is a pretty delicate molecule, prone to oxidization. Typical process cholesterol used to add to these diets is usually oxidized cholesterol, which does promote some problems. So, it would be nice to know if the cholesterol used in this study was oxidized.
The main problem, however, is that mice normally don’t eat much, if any, cholesterol and don’t eat large amounts of fat, so it stands to reason that they would respond more dramatically to the addition of these substances to their diet. (Humans haven’t typically eaten much carbohydrate in their native diet, i.e., in evolutionary terms, and look what happens when humans are plied with large amounts of dietary carbohydrate.) The largest problem, though, is that they are mice—not humans. These kinds of studies are valuable for determining how things work on a molecular level—and to that extent I find this one interesting—but the data can’t be extrapolated to humans.
The last human saturated fat study I read was in the November, 2004 issue of the American Journal of Clinical Nutrition. It showed that a greater saturated fat intake was associated with less progression of coronary artery disease in women. In HUMAN women.
You should take all these mice/rat/rabbit studies with a grain of salt. They make great headlines in the lay press, but they usually don’t mean much in human terms.