> It's from amino acids, and the process is called gluconeogenesis.
> Glucose is essential for some brain cells, retinal cells, red
> blood cells, and fast-twitch muscle cells.  There may be others,
> but those are the ones I know about.

thanks for the info. If I can trouble you with a follow-up or two...

is the conversion one-to-one or less efficient, ie how many grams of amino
acids it takes to produce one gram of glucose?

so the main difference between a long fast and a very low-card diet is
simply that in the fast amino acids are cannibalised from skin and muscle
tissue instead of acquired through food?

if in low fat diets ketones are excreted as a by-product of fatty acid
metabolism, is there any significant by-product - healthy or unhealthy -
from amino-acid gluconeogenesis?

thanks
Andrew