On Thu, 11 Jul 2002, Phosphor wrote:

> > Ketosis is stress for anyone, for the simple reason that blood
> > glucose must be maintained, and stress hormones are the body's
> > signal to do that.
>
> i don't think this can be right. the whole point of ketosis is to stop using
> glucose. One of the ketones effectively shuts down the gluconeogenesis
> process [whether completely I'm not sure]. this is why protein requirements
> drop significantly.

It is physiologically impossible to stop using glucose.  Cells
that lack mitochondria cannot burn ketones or fat; they must have
glucose.  All red blood cells lack mitochondria, and therefore
must burn glucose.  I understand that there are some brain cells
that also absolutely require glucose, but sources vary quite a
bit on how much they need.  When glucose is available, the brain
uses about 150g/day.  After full adaptation to ketones, the
lowest figure I've seen is 35g/day still needed by the brain.
And fast-twitch muscle fibers need glucose.  But you are correct
that during ketosis glucose utilization drops significantly, and
therefore so does the need to produce it from protein.  But it
doesn't drop to zero.

The other thing that happens during extended ketosis is that less
gluconeogenesis happens in the liver and more happens in the
kidneys.  So it's true that hepatic gluconeogenesis shuts down
(pretty much), but renal gluconeogenesis picks up the slack.

The bottom line is that when carbs are sharply limited, glucose
is still being utilized, although at a much lesser rate than
usual.  And even in ketosis, blood glucose must be maintained at
at least 60 mg/dl.  If it falls below that -- as it must if
hardly any carbs are being eaten -- it must be replaced.

For most people under most conditions, I think the replacement of
glucose by means of gluconeogenesis goes smoothly and there's no
problem.  But it is a fact that those stress hormones are
integral to that process, and if for some reason the process is
sluggish, there would be problems.

It's possible that the weight training I was doing increased the
demand for glucose as I was switching from hepatic to renal
gluconeogenesis and, for some reason, my kidneys couldn't keep
up.  Who knows?

Todd Moody
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