Wayne, I copied part of a review of the book "Life Without Bread" from
Amazon.com because the reviewer gives a concise explanation of why Dr. Lutz
recommends 72 carbs per day.  That number is my personal target.  I am not
sure, however, that this is a magic number for everyone.  Below is the
quote:

"This is great book, that will explode many of the myths in your head about
what is "good" and "bad" for your health. Contrary to many of the reviews
written here, I did not find it "overly technical" at all, in fact it was
very easy reading and I read it in a couple of days. The dietary
recommendations are very simple to follow, and all recommendations are
backed with rock-solid evidence, and most importantly, the evidence is based
ON REAL LIFE EXPERIENCE OF ACTUAL PATIENTS unlike so many other books out
there. This must have been an amazingly brave book when it first came out...
in 1968! It is still a pioneering work, and if you are interested in
learning about low-carb diets with an open mind this is really a must-have
for your collection. HIGHLY RECOMMENDED. btw, the "72 carb/day"
recommendation is based on their studies of how many carbs/day diabetics can
consume without affecting their blood sugar, and is also how much carbs per
day the brain needs to run on (the brain cannot run on fat). that explains
the figure. they explain this and everything else very thoroughly in the
book"

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How much is too much carbs?

Wayne