From:
Bob C
Date: 2001-11-12 00:19:00 UTC
Subject: Bob C: Thiamine and all that other stuff
Ok, I'll make this quick. From off my bookshelf:
1. Most fish are rich in thiamine [or thiamin], and eating them does not
cause thiamine deficiencies. Tova Navarra and Myron A. Lipowitz 1996
Encyclopedia of Vitamins, Minerals and Supplements. Facts on File; NY.
P. 183.
2. Thiaminase is an enzyme found in RAW fish (not cooked; raw) that
destroys thiamine. Carolyn D. Berdanier. 1998 CRC Desk Reference for
Nutrition. CRC Press; Boca Raton. P.323.
3. Thiaminase is found in fish where it is concentrated in the viscera,
and for this reason fish meal is generally thiamine deficient. A
similar enzyme is found in RICE. J. Adrian, G. legrand and R. Frangne.
1988 Dictionary of Food and Nutrition. Weinheim; NY. P 193.
I have 6 other volumes which support these statements, but the point is
made. There are several handbooks which list the body composition of
certain fish, and are generally available in larger university and
medical libraries. I do not own one of these expensive tomes, and since
I am answering this question well after library closing hours, it is
impossible for me to look up values for specific fish. Rest assured,
however, such values exist and can be easily referenced. The values may
even be available online.
Reviewing the reports of the Vitamin B1 deficiency (= thiamine) in
ferrets, the ferrets in question were being ranched for their fur
(called fitch ferrets), and were being fed a homemade food containing
large amounts of fish waste. The ferrets developed classic symptoms of
beriberi, became ill, and most died or were destroyed. This happened at
several other fitch farms, and quite a number of mink farms. In all
cases, investigations showed the problem was in feeding the large amount
of waste fish, which included heads and viscera scraps. Similar
outbreaks of beriberi in mink were reported, resulting from diets
containing large amounts of grain carbohydrates and low in thiamine, but
not linked to fish diets.
Cooking destroys both thiamine and thiaminase, so feeding cooked fish
will not cause a problem. The muscle of raw fish is rich in thiamine,
and while it also contains thiaminase, there is so much thiamine present
to power the pentose-phosphate cycle, as well as in the oxidative
decarboxylation of carboxylic acids (= pyruvic and ketoglutaric) that
eating the muscle from raw fish while discarding the viscera presents
little danger to the consumer. As already pointed out, thiaminase is
concentrated in the viscera, while thiamin is concentrated in the
muscle. For example, in eel, thiamine is found in 0.2% of the edible
meat (0.1 in salmon and trout, 0.15% in oysters), while in beef, it is
0.1%. Pork is 0.7-0.8%! Thiaminase is generally considered to be equal
or less than thiamine concentrations within the same animal. What is
important to remember is that thiamine is concentrated in the muscle
tissue, and thiaminase is concentrated in the viscera.
As for egg whites, the substance which binds to Biotin is called Avidin.
When avidin binds to Biotin, the resulting molecule is indigestible
and is eliminated in the feces. Avidin is present in raw egg white
(0.5% of the nitrogen content), but is easily denatured by cooking.
Biotin deficiency was once called "egg-white disease", and was common in
people and animals consuming large amounts of raw egg white.
In both cases, occasional snacks of raw fish viscera and raw egg whites
will do little harm to your ferrets. Thiamine and Biotin deficiencies
take weeks to develop when the primary diet is deficient in the
vitamins. Even if you fed your ferrets a meal of these foods each day,
the lowered vitamins would be a small blip on the graph provided the
rest of the diet was sound. If it worries you, just add a bit of
Ferretone or Nutrical paste (or other approved ferret or cat vitamin) to
the ferret's daily diet. If you do that, the point is moot and your
worries are over.
Bob C