C. ten Broeke wrote:
>>
>> Lack of Thiamin causes beriberi, doesn't it? Beriberi was once a major
>> disease in Japan, before they started eating a more "western" diet.
>>
> Not necessarily.  I heard a few times that when the Japanese ate brown
> rice they had no beri-beri.  Only when the westerners came who preferred
> polished rice and they adapted to that kind of eating they developed the
> disease.

That's true, and not only in Japan.
Thousands of people eating white rice developed beriberi because they
were missing the thiamin which is in the outer "sliver skin" of the rice
(or other grains).
After they discovered thiamin, all white rice is now enriched with
thiamin. If you look at USDA data for example, white rice contains as
much of thiamin as brown rice. It's added.

Lack of thiamin disables glycolysis - means glucose cannot be used for
fuel - and cannot converted to fat too.
Fat enters into the Krebs cycle without glycolysis.
But the Krebs cycle needs some thiamin at a later stage - so even if you
eat very little carb you still need thiamin.
For oxidizing fat and for glycolysis of the carbs which needs the brain,
and for the glucose wich is derived out of protein too.
Some amino acids have to go through glycolysis after gluconeogenesis,
some others enter later into the pathway.

Thiaminases (from raw fish)  could only purge the thiamin in the same
stomach or gut content (I presume).
So, unless you eat raw fish every day, you have some other days left to
ingest the thiamin. Thiamin storages in the body are estimated to last
max. 19 days.
There are other factors which hinder the entry of thiamin into the body,
namely black tea and coffee (?) come to my mind.

Btw grains: they contain more thiamin as is necessary to break down the
carbs contained in the same grain. As grains are cooked usually, cooking
destroys some of the thiamin (up to 40%) and some more leeches out into
the cooking water (it's water soluble).
Due to the fact that they contain more as necessary, enough thiamin can
remain after cooking to use the carbs.
Nevertheless traditional cooking techniques require the cooking water to
be used too. When cooking rice, all the cooking water should be absorbed
into the rice - so nothing is lost.

IMO this was a prerequisite for grains to be used as food.
White flour products (and sugar) of course deliver much too less thiamin
- the glucose cannot be used properly and will accumulate, leading to
heavy insulin surges. Attempt of the body to lower glucose, but body
cells beeing unable to use it as fuel.

regards

Amadeus S.