Vitamin C Supplementation
My-Dog.info > Dogs, Diet & Food
The popularity of vitamin-mineral supplementation in the human
health field, and in particular the prevalence of vitamin C
supplementation, is unquestionable. Despite the fact that dogs
and cats manufacture vitamin C on their own in the liver, the
need for dietary vitamin C in pets continues to be discussed by
both pet owners and veterinarians.
Vitamin C, or ascorbic acid, is required for the formation of
collagen. Collagen is a primary constituent of teeth, bone, and
connective tissue, and is produced by bone-forming cells during
skeletal growth and development. Ascorbic acid is produced in the
liver from two sugars, either glucose or galactose. Unless
inadequate amounts are synthesized by the liver or there is an
unusually high metabolic requirement, supplementation of the diet
with ascorbic acid is unnecessary.
Ascorbic acid may occasionally be included in a petfood
because of its ability to act as a natural antioxidant. However,
since it is water soluble and not easily combined with the fats
in petfood, its effectiveness as an antioxidant is limited.
However, when combined with other antioxidants such as vitamin E
and butylated hydroxytoluene, ascorbic acid has been shown to
work cooperatively with these antioxidants.
Whether or not supplementation of a canine or feline diet with
vitamin C is necessary, particularly during times of increased
demand, remains controversial. Vitamin C requirements do increase
with stress and many pet owners, breeders, and veterinarians
believe that stressed animals may be unable to manufacturer
sufficient ascorbic acid themselves to deal with stressful
situations. This belief was most likely based on a study
involving human athletes which indicated that ascorbate levels in
the blood were found to decline during stress. However, several
subsequent controlled studies with human athletes showed vitamin
C supplementation to have no beneficial effects on work capacity.
No studies at present support the need for vitamin C
supplementation for working and stressed dogs.
Further support for vitamin C supplementation arose from a
published report that suggested hypertrophic osteodystrophy
(HOD), a bone disease of young dogs, might be due to a deficiency
of vitamin C within the body, based on a report that found
similarities between bone abnormalities found in HOD and scurvy
(vitamin C deficiency) in humans. Later evidence showed that the
two conditions were not the same disorder and controlled studies
on the efficacy of supplementing with vitamin C in the treatment
of HOD failed to support the concept that low levels of ascorbic
acid were a cause of HOD.
The association between vitamin C and skeletal disorders in
general persisted, and eventually included several other
developmental bone disorders, including osteochondritis dessicans
(OCD) and canine hip dysplasia (CHD). Growing dogs were
supplemented with ascorbic acid in the hope that these diseases
might be prevented. However, there is no evidence to support the
preventive efficacy of such supplementation.
In humans, the general belief is that vitamin C is at best
beneficial and at worst, harmless. Ascorbic acid supplementation
in dogs and cats, on the other hand, may be detrimental under
certain circumstances since any excess ascorbic acid is excreted
as oxalate in the urine. Elevated concentrations of urine oxalate
may play a role in the formation of calcium oxalate crystals or
stones in the urinary tract. For this reason, avoidance of
ascorbic acid supplementation is currently recommended for the
prevention of calcium oxalate urinary crystals or bladder stones.
Reprinted with permission from www.animalhealthcare.ca
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