Did you know the need to breath oxygen creates products that can also damage cells? These same destructive molecules are necessary when the immune system fights infection or when the body detoxifies harmful chemicals. These molecules are called “free radicals” or “reactive oxygen species” (ROS). In addition to causing cell damage and death, it is also thought that free radicals contribute to cancer, diabetes, senile deafness dementia and aging in humans and dogs. Because free radicals are necessary the body has developed ways to minimize their damage. Antioxidant vitamins are one of the body’s means to control free radical side effects. Vitamins C and E are powerful antioxidant vitamins.
Vitamin C and E protect cells from damage and death caused by free radicals by protecting the polyunsaturated fats in cell walls. They minimize the ability of free radicals to alter DNA and prevent cell cycle changes that are thought to lead to cancer. Chronic inflammatory conditions like skin allergies, arthritis, and certain bowel and kidney diseases produce large amount of free radicals. Alzheimer’s disease in humans and senile deafness and dementia in dogs are also thought to be the result of chronic inflammation in the brain. Vitamin C and E have long been recommended for the treatment of inflammatory conditions to minimize free radical damage. They are routinely recommended for the treatment of the conditions mentioned above.
Dogs can actually make vitamin C in their bodies during sugar metabolism. Whether this natural amount is adequate to control free radical damage is unknown. Natural production capabilities might also vary from dog to dog. Most dog foods have minimal amounts of vitamin E and few contain any vitamin C.
Citrus fruits, peppers, kale and tomatoes are all known to have large to small amounts of vitamin C. The seed oils of wheat germ, sunflowers and safflowers are the highest source of vitamin E. Nuts and nut oils contain moderate amounts while some leafy green vegetables contain small amounts of vitamin E. However, the amount of vitamin C and E in these natural sources is still insufficient unless the dog was willing to eat large amounts of these foods. With seed oils, that would substantially increase the fat content of the diet.
Vitamin C and E supplements provide greater amounts of vitamin E. Many fish oils also contain larges amount of vitamin E. Vitamin C and E are not known to be toxic in the dog, but they should be used carefully.
Vitamin C is converted to oxalate that is filtered from the kidneys into the urine. Oxalate urinary crystals and stones are a problem in some dogs and vitamin C supplementation could make the condition worse for these animals. Extreme doses of vitamin E interfere with the intestinal absorption of vitamins, A, D and K. Safe daily dosages of vitamin C and E range from 10 mg for small dogs to 100 mg for large dogs. Vitamin E is sometimes labeled in International Units or IU and each IU is equivalent to a mg. Higher doses may be used to treat specific medical conditions. Check with your veterinarian for specific doses for your dog(s) before supplementing with vitamins C and E.
~Dr Ken Tudor
THE DOG DIETITIAN