Amadeus Schmidt wrote:
> -protein will be converted to carbohydrate
>  Because some carbs are essential, and there is *no* means
>  for the body to recreate carbohydrate from fat
Not true - the are no means to convert fatty acids to glucose,
but fat (tryglycerides) also have a glycerol molecule, which
can be converted to glucose and depending on the type of
fat, can contribute a noticeable amount of energy. Fats
composed of very short chain fatty acids (such as found in
butter) may have 5-10% of their energy coming in the form
of glucose.

As for the bodys need for glucose - it depends on what you
are eating. Lyle (on the low carb lists) periodically posts
references to studies showing that the need for glucose
drops after a few (about 3) weeks on a ketogenic diet to,
if I am not mistaken, about 40gm per day. He also posted
references to studies showing that 58% of protein you eat
converts to glucose. This means that even on a rather moderate
protein diet a person would get enough glucose for the
daily needs of the brain.

Btw, I was wondering if anyone here can shed a little light
on this (this might be a very stupid question, but I am not
a brain scientist, so please humor me)- it's said that brain
(at least the part that sits on the inside of the
blood-brain barrier) requires glucose since the fat based
energy sources can't pass that barrier. Well, about 40% of
the brain is composed of fat and much of that being the
highly unsaturated fats derived from w-3 and w-6 fats. Since
the original w-3/2-6 can't be made in the body they must have
made their way into brain from outside the brain (derived
from the food). Then, if fatty acids can make it into the
brain, then why is it that brain can't use them for energy?

Ilya