S.B. Feldman wrote:
> <<  Some cells, such as the cells in fast-twitch muscle fiber
>  and certain brain cells, have to have glucose, so these would
>  need adequate B1 to use it.  In short, the B1 requirement may
>  depend upon whether or not one is in ketosis. >>
> Tissue slice studies have shown that ketone bodies are utilized preferentially
> to glucose, I have heard Atkins say this on several occasions, specifically to
> address this glucose and the brain claim.
There are three types of muscle fibres - type I, type IIa, and type IIb. (slow,
medium, fast twich fibers). Slow use ketones, medium can use either glucose
or ketones, fast use glucose.
As for the brain, the amount of ketones used depends on how long one has been
in ketosis and what part of the brain you are talking about. The minimum
amount of glucose for the brain (according to Lyle McDonald who is a frequent
contributor to the lowcarb-exercise list and has references to back this up)
is about 40gm after the full adaptation to ketosis.

Ilya