Lyle McDonald on Dietary Cholesterol and Fat and their Impact on Blood Cholesterol

"1. Cholesterol intake per se tends to have a minor effect on total blood
cholesterol. first and foremost, your liver makes more cholesterol on a
daily basis (anywhere from 1.5-2 grams/day) than you would generally eat
(well, 2 grams per day of cholesterol would be 7 whole eggs). On top of
that, liver cholesterol production adapts to your intake. So when you
eat more cholesterol, the liver typipocally downgrades its own
cholesterol production ; when you eat less cholesterol, the liver
upregulates its own cholesterol. This is all basic physiology, in any
decent textbook.

1a. However, there is a wide range of difference in how people respond
to dietary cholesterol per se. There are both hypo and hyperresponders
meaning that some people are sensitive (in terms of total cholesterol
levels) to dietary cholesterol intake. But certainly not all.

2. The bigger issue in blood cholesterol intake has to do with fatty
acid intake NOT cholesterol intake. For example, most saturated acids
tend to raise blood cholesterol levels by affecting liver metabolism
(differently than dietary cholesterol intake does). There are
exceptions, such as stearic acid which is saturated but doesn't affect
blood cholesterol intake. Monounsaturated fats (olive oil, which is
oleic acid, being the primary one) has a neutral effect on blood
cholesterol levels. Polyunsaturated fats (w-6 and w-3) have cholesterol
lowering effects, in general.

3. Now, *in general* foods high in cholesterol are also high in
saturated fats but this is not always the case. Even lowfat foods such
as chicken and lowfat fish contain cholesterol because it is part of the
cell membrane. Eggs contain both cholesterol and saturated fat
(although there are more polyunsaturated fats in eggs than most people
realize, you can check the USDA database to check that). Same with
fatty cuts of red meat: both cholesterol and saturated fats are present
(note that red meat actually contains mostly oleic acid, and a good bit
of the saturated fat is stearic which I already mentioned doesn't affect
blood cholesterol negatively). At the other extreme, there are foods
like coconut and palm kernel oil which are highly saturated but contain
no cholesterol. So while the two are generally associated food wise,
it's not an absolute case.

4.Chronically high insulin levels (which can occur when you tell peope
to replace fats with carbohydrates, depending on their carb choices)
also affect blood lipid levels (insulin stimulates HMG-CoA reductase
which is the rate limiting enzyme for cholesterol synthesis in the liver
; high insulin also raises blood triglyceride levels which is an
independent risk factor for heart disease).



Ok, so what about eggs. The original backlash against eggs had to do
with their cholesterol content, because at the time cholesterol intake
was being blamed for high blood cholesterol levels, which we now know
has only a minor effect. That's part of why you'll hear the 'bull****'
on 'eggs raise blood cholesterol'.

But, you ask what about the fat content. Looking at the USDA database, a
whole egg is listed as having

Total lipid (fat) Gms : 10.020 10.4% 13.7%
OF which the following major fatty acids appear (there are trace amounts
of some others but I'm leaving them out).

Palmitic acid (16:0) Gms : 2.226
Stearic acid (18:0) Gms : 0.784
Oleic acid (18:1) Gms : 3.473
Linoleic acid (18:2/n6) Gms : 1.148 17.9% 23.4%

Ok, 2.2 grams of palmitic, which is a cholesterol raising saturated fat.
0.7 g of stearic acid, a neutral saturated fat.
3.4 g of oleic acid whith is neutral
1.1 g of w-6 which is a cholesterol lower polyunsaturated fat.

So of the 10 total grams of fat, 2.2 grams are negative in terms of
cholesterol, 4.1 are neutral, and 1.2 is positive.

Hardly the death in a white shell that they are made out to be.

So that's the basic gist of it.
Yes, excessive saturated fat has a negative impact on cholesterol.
For some people, excessive cholesterol can have an additional minor effect.
Yes, saturated fat and cholesterol tend to accompany one another but not always.
The rest of the diet (fiber, w-3/w-6 intake from other foods) has to be
taken into effect.

And that doesn't even bring the effect of exercise into the equation."