by JeffN » Wed Nov 23, 2011 10:12 am
Let me post Dr Castelli's personal comments in response to that often misrepresented quote...
He says he was observing that in one of the first dietary history
studies done at Framingham a data set was used which showed that
those who ate the most saturated fat had the lowest cholesterol
readings. That seemed surprising at the time. But even more
surprising, the same data also indicated that those in the group who
ate the most calories weighed the least.
Since eating more and weighing less appeared contradictory, this
raised questions. They realized something must be awry, so they set
out to determine what it was. The answer turned out to be that in
this particular group of subjects those who ate the most saturated
fat also had the highest energy expenditure. So that, although they
ate more, they weighed less because they were burning a lot more
calories. Also relevant was the fact that exercise appreciably
reduces blood cholesterol in the very short term.
So, in order to figure out whether it was eating saturated fats that
was lowering cholesterol, or the exercise instead, they investigated
further. Specifically, a direct quote cut-and-pasted from Dr.
Castelli's recent communication:
".... how do you know that eating cholesterol and saturated fat raise
your serum cholesterol? You have to do a metabolic ward study. Being
on a metabolic ward is like being in prison and the two best studies
were done in Minneapolis (Dr. Ancel Keys) and Boston (Mark Hegsted).
They would increase the cholesterol and saturated fat in your diet,
controlling for everything else and showed the more cholesterol you
ate, or the more saturated fat you ate, the higher you serum
cholesterol went.
In other words it was the higher physical activity that had accounted
for the lower blood cholesterol's of the subjects in the earlier
study - exercise was the confounder that had not been controlled for.
Further, he goes on:
"Virtually all the early diet trials were based on removing saturated
fat and cholesterol from you diet and lowering your serum
cholesterol. They also showed that the better they did this, the
better was the fall in coronary heart disease."
So, Dr. Castelli is saying, not only did lowering saturated fat
intake drop cholesterol, it also reduced heart disease. And further,
Dr. Castelli says:
"....... the latest diet data from Framingham showed that the women of
Framingham who ate a high fat, low calorie diet doubled the deposits
in their carotid arteries compared to women on a heart healthy diet."
And still further he notes that the impact on lipids of a high
saturated fat diet is even greater than that measured by standard
cholesterol tests. This is because the tests are normally done after
an eight to ten hour fast. But the atherogenic effects (chylomicron
remnants) peak around the time the meal is eaten and then diminish
dramatically as the hours go by. So they are much greater in the
period immediately following a high fat meal than when the tested
blood is normally drawn many hours later.
In Health
Jeff