From: sasjyb@castanea.unx.sas.com (John McDonald Brown III)
Subject: FUS diet
Organization: SAS Institute Inc.
Date: Thu, 16 Apr 1992 18:19:39 GMT
X-Bytes: 3161

>hannah@pomponio.ai.sri.com (Marsha Jo Hannah)
>
>In article <4dtMufu00iV181Dqkv@andrew.cmu.edu> sw39+@andrew.cmu.edu (Susan R. Wagner) writes:
>
>   Just a thought, would giving occasional treats of orange slices cut up
>   be equivalent to the 100 mg vitamin C tablets?  Also, did your vet
>   recommed this for your cat who does not have FUS?  Does anyone know if
>   you were to give orange treats to a male neutered cat who does not
>   suffer from FUS, would it cause any problems or just help prevent future
>   FUS?  Just some thoughts and questions.  The vitamin C is something I
>   never thought about.  Very interesting!
>
>I don't recall exactly how much vitamin C there is in an orange, but I
>think it's on the order of 50 mg or less.  You'd have to feed a lot of
>orange slices to get up to the 250 mg dose that our vet recommended,
>DAILY.  The vet said it would be OK to give C to our other cat, as
>well, although being female, she was far less likely to have a problem
>with FUS, so we haven't bothered (she hates taking pills).  My
>understanding is that vitamin C, being a water soluble vitamin, is
>pretty safe to give in mega-doses (i.e. doses beyond the cat's dietary
>needs, which are small)---the cat will simply dispose of the excess in
>its urine (which is the whole idea in treating FUS with C---the large
>excess of C is needed to acidify the urine).
>
>Marsha Jo Hannah


I was astounded when I read this. My understanding of vitamin
C was that only a handful of the species that inhabit this planet
harbor the genetic defect that results in a dietary requirement for
vitamin C. I didn't remember cats as being one of them. I had read
some time ago in _Harrison's Priciples of Internal Medicine_ that
we (humans) lack the genetic info for a single enzyme in the
metabolic pathway for the production of vitamin C.

I went to a nearby veterinary medical library last night to
check this out. The book _Vitamins in Animal Nutrition_
describes the missing enzyme as L-gluonolactone. Animals
that lack the enzyme are primates (including humans),
guinea pigs, fish, fruit-eating bats, insects, and some
birds. The book states "In general, domestic animals such
as [....], dogs and cats have the ability to biosynthesize
ascorbic acid within thir body and hence there is no
recommended requirement established by the national research
council." and later... "Low blood ascorbic acid can be caused by
various types of stress including [..lots of stuff..]. Under
such conditions, exogenous vitamin C can have a positive
effect in ascorbic acid synthesizing species."

Another book, _Vitamin tolerance of animals_, sites several
studies (non of them controlled) that indicated sensitivity
to high levels of ascorbic acid in domestic animals. It
repeatedly called for further studies.

I didn't have time to look for journal articles relevant
to treatment of FUS with vitamin C, but neither of these
books mentioned it. I would appreciate any references.
I remain skeptical of the practice of administering
vitamin C to an animal species that makes its own. Its
hard to argue with success, though.

                           -- John Brown