Common Uses
Supplement for arthritis, allergy, epilepsy, cancer prevention, immune support
Vitamin C is a water soluble vitamin that is required by people and some animals. Humans and certain animals (such as guinea pigs and monkeys) lack the enzyme L-gulonolactone oxidase needed for the formation of vitamin C. Dogs and cats possess this enzyme and can therefore synthesize vitamin C. As such, dogs and cats do not have a specific dietary requirement for this vitamin. Many doctors, however will supplement with vitamin C during times of stress and illness (as larger amounts of vitamin C may be required during these times.)
Ascorbic acid is a term often used interchangeably with vitamin C. While ascorbic acid (as well as ascorbate and other terms) is often used synonymously with vitamin C, this is not technically correct. Ascorbic acid (discovered in 1928, when Albert Szent-Gyorgyi isolated the active ingredient in fruits and called the “anti-scorbutic principle”) is the antioxidant fraction of vitamin C. Simply supplementing ascorbic acid is not the same as supplying vitamin C. Holistic veterinarians usually prefer natural vitamin C supplementation when indicated, although studies using the complementary therapy called orthomolecular medicine have shown benefit to using ascorbate in helping pets with a variety of medical disorders. A novel product called Ester-C has also shown benefit in pets.
Vitamin C functions as an antioxidant and free radical scavenger, is used for normal repair of tissue, is required for adrenal gland function, is used for collagen synthesis, and is needed for maintaining healthy gums. It is needed for metabolism of several B vitamins, including folic acid and the amino acids tyrosine and phenylalanine. Vitamin C is needed for norepinephrine (a nerve transmitter) synthesis as well as for cholesterol synthesis.
Therapeutic Uses
This vitamin assists in providing protection against cancer and enhances immunity. Hemoglobin synthesis requires vitamin C; deficiency can cause anemia.
Because vitamin C is so vital for the synthesis of the connective tissue collagen, which is an integral part of cartilage, it is often prescribed for pets with arthritis (and various forms of vitamin C or ascorbate acid are often included in various supplements for pets with arthritis.)
To have normal collagen metabolism, vitamin C is required for the conversion of proline to hydroxyproline and for the conversion of lysine to hydroxylysine. These reactions take place after proline and lysine are incorporated into the connective tissue.
Vitamin C also protects against unnecessary blood clotting and bruising and aids in healing of wounds; vitamin C deficiency causes slow scar formation.
Ascorbic acid is a precursor of oxalate. It has been suggested that additional ascorbic acid should not be feed to pets prone to oxalate bladder stones. However, at least in people, there is no evidence that high levels of ascorbic acid actually increase oxalate production.
Vitamin C appears to work synergistically as an antioxidant with vitamin E. Vitamin C appears to attack free radicals, those chemicals produced as a by-product of cell metabolism, in cellular fluids, whereas vitamin E attacks the free radicals in the cell membranes.
In people, vitamin C has been recommended for numerous conditions, including colds, cataracts, macular degeneration, cancer prevention and treatment, heart disease prevention, hypertension, asthma, low sperm count, bedsores, Alzheimer’s disease, diabetes, hepatitis, herpes, insomnia, osteoarthritis, Parkinson’s disease periodontal disease, preeclampsia, rheumatoid arthritis, ulcers, allergies, general antioxidant, bladder infections, menopausal symptoms, migraine headaches and nausea.
Ascorbic acid scavenges nitrates, which can reduce nitrosamine- induced cancers.
There is some evidence that supports using vitamin C supplement to help colds, slightly improve asthma and reduce the risk of macular degeneration and cataracts.
In people, vitamin C deficiency cause scurvy with the clinical signs of swollen, painful joints, abnormal wound healing, bleeding gums, and pinpoint hemorrhages under the skin. Vitamin C deficiency, while common in non-human primates (monkeys) and guinea pigs, does not occur in dogs and cats.
Scientific Evidence
Regular use of vitamin C may reduce the risk of cataracts, probably by fighting free radicals that damage the lens of the eye. In an observational study or 50,800 nurses followed for 8 years, it was found that people who used vitamin C supplements for more than 10 years had a 45 percent lower rate of cataract development. However, unlike the case of other supplements, diets high in vitamin C were not found to be protective; only supplemental vitamin C made a difference. This is the opposite of what was found with vitamin C in the prevention of other disease, such as cancer.
It had been suggested that vitamin C may be particularly useful against cataracts in people with diabetes, because of its influence on sorbitol, a sugar-like substance that tends to accumulate in the cells of diabetics. Excess sorbitol is believed to play a role in the development of diabetes-related cataracts, and vitamin C appears to help reduce sorbitol buildup.
Vitamin C levels in the blood have been found to be low in people with diabetes. When vitamin C levels are adequate, the regulation of insulin improved, as vitamin C has been shown to enhance insulin action glucose and lipid metabolism. Therefore, vitamin C supplementation may benefit both insulin-dependent and non-insulin diabetics. It is unknown if this is the case in diabetic pets, although vitamin C has been recommended for pets with diabetes.
There is also good evidence for using ascorbate for people with gingivitis. Evidence for its effectiveness in treating their conditions is highly preliminary at best.
In people, aspirin, other inflammatory drugs, corticosteroids, and tetracycline-family antibiotics can lower body levels of vitamin C. The same may be true of pets, vitamin C given to pets treated with the medications mentioned above is not harmful and might be helpful.
Pets are often treated with additional vitamin C or ascorbate compounds for various illnesses. Both intravenous and oral supplementation are used, although controlled studies are lacking showing the effectiveness of giving vitamin C or ascorbate compounds for most conditions.
Sources
Citrus fruits, green vegetables, berries, broccoli, Brussels sprouts, collard greens, spinach, chard, turnip greens, red chili peppers, sweet potatoes, kale, parsley, watercress, cauliflower, cabbage and strawberries are good sources of vitamin C, as are green foods, alfalfa, herbs, rose hips dandelion, fennel and slippery elm.
Safety Issues
In pets and in people, high-doses of vitamin C may cause diarrhea. There have been warnings that long-term vitamin C treatment can cause kidney stones, but in a large-scale study the people who took the most vitamin C (over 1,500 mg daily) actually had a lower risk of kidney stones than those taking the least amounts. Nonetheless, people with a history of kidney stones and those with kidney failure who have a defect in vitamin C or oxalate metabolism should probably restrict vitamin C intake to approximately 200 mg daily. While there is no evidence that stone formation increases people or pets supplemented use with vitamin C, talk with your veterinarian before adding extra vitamin C if your pet is prone to urinary stones.
Vitamin C may also reduce the blood-thinning effects of Coumadin (warfarin) and heparin.
Vitamin C may increase the blood levels of some drugs, such as aspirin and other salicylates.
Always consult with your veterinarian before adding vitamins and supplements to your pet’s diet.
