Vitamin C, has a chemical structure that is closely related to the monosaccharide sugars. It is synthesized from glucose by plants and most animal species, including dogs and cats.
When present in foods, Vitamin C is easily destroyed by oxidative processes. Exposure to heat, light, alkalies, oxidative enzymes, and the minerals copper and iron all contribute to losses of vitamin C activity. Oxidative loss of vitamin C is inhibited to some extent by an acid environment and by the storage of foods at low temperatures.
The body requires ascorbic acid for the hydroxylation of the amino acids proline and lysine in the formation
of collagen and elastin and for the synthesis of acetylcholinesterase. Collagen is the predominant structural
protein in animals and is a primary constituent of osteoid, dentine, and connective tissue.
In animal species that have a dietary requirement for vitamin C, such as humans,a vitamin C deficiency results in a condition called scurvy.
Clinical signs of scurvy include impaired wound healing, capillary bleeding, anemia, and faulty bone formation. Bone abnormalities that are associated with scurvy are the result of impaired cartilage synthesis.
All animals are capable of producing adequate levels of endogenous vitamin C and therefore
do not have a dietary requirement for this vitamin.
Vitamin C is produced in the liver from either glucose or galactose through the glucuronate pathway. The adult dog produces approximately 40 milligrams per kilogram (mg/kg) body weight of ascorbate each day.
This is a relatively low amount compared to other mammalian species. However, controlled research
studies in the dog have shown that dogs do not require an exogenous source of vitamin C for normal development
Similarly, no requirement for dietary ascorbic acid has been demonstrated to exist in the cat.
Most vitamins cannot be synthesized by the body and must be supplied in food. Well-balanced pet foods are
formulated to provide the necessary supplementation. Vitamin C, however, is one vitamin that can be synthesized
from glucose by dogs and cats; in contrast, humans must receive vitamin C from dietary sources.
In recent years a number of breeders, dog show enthusiasts, and pet owners have been routinely administering
high levels of supplemental vitamin C to their dogs’ diets in the hope of preventing or curing certain
developmental skeletal disorders. Currently the use of high amounts of supplemental vitamin C in the diets
of healthy dogs and cats is not recommended and may even be contraindicated.