Vitamin E is an essential vitamin for dogs, which means they must consume a certain amount of it in their diets. Forms include the fatty alcohols alpha- and gamma-tocopherol. Tocopherols are added to most dry dog foods, but they have low shelf stability, so some dogs may require additional vitamin E supplementation. Vitamin E oil is also sometimes used to treat canine skin conditions such as dry, flaky areas and hot spots.
What Vitamin E Does
Vitamin E is an antioxidant, which means it helps cells protect against and repair damage caused by free-radicals, reactive atoms that form as a byproduct of oxygen metabolism. Some nutritionists have deduced that the form alpha-tocopherol is more important than gamma-tocopherol because the body tends to retain it longer. However, gamma-tocopherol specifically removes nitrogen oxides, radicals not strongly targeted by alpha-tocopherol. Relative importance of the two types of tocopherol is unknown, but your dog's body uses vitamin E to support her immune system, form red blood cells and prevent blood clotting disorders. Severe vitamin E deficiency, or hypovitaminosis E, causes degeneration of the skeletal, cardiac and smooth muscles; causes digestive tract lining and retina degeneration; and can cause reproductive failure in both sexes. Severe deficiency can cause fluid buildup beneath the skin, depression, refusal of food and water, coma and death.
Dog Food and Vitamin E
Most well-formulated dry dog foods contain vitamin E beyond the recommended daily allowance. However, this added vitamin E tends to degrade over time, and feeding practices can reduce the amount of vitamin E your dog actually consumes. For example, adding supplemental foods reduces the amount of dry dog food your pet eats and thus the amount of vitamin E she receives. In addition, the body uses vitamin E to process polyunsaturated fats, so supplemental vegetable and fish oils particularly impact how much vitamin E is available for the body to use for other purposes such as cellular repair and generation.
Benefits of Supplementation
Minor vitamin E deficiency is associated with conditions that cause dry, itchy, flaky skin. One such condition is canine atopic dermatitis, a severe allergic skin reaction caused by contact with an irritant. A 2014 study led by Dr. Tina Kotnik confirmed that dogs suffering from CAD had unusually low levels of vitamin E in their skin and blood. Oral vitamin E supplements increased vitamin E levels and decreased atopic dermatitis symptoms in these dogs. Oral supplementation also appeared to reverse muscle degeneration and reproductive failure in deficient dogs.
Risks of Supplementation
While no toxic dose of vitamin E is known, it's possible to get too much of a good thing. Vitamin E increases the body's ability to absorb other fat-soluble vitamins, including the potentially toxic vitamin A. Excessive levels of vitamin E may also lead to decreased blood coagulation and bleeding disorders by blocking proper absorption of vitamins D and K. This can be especially dangerous if a dog is exposed to toxins that cause internal bleeding, such as rodent poisons. In addition, the differences between how the body uses nutrients from food versus those from supplements are still incompletely understood, so consult your veterinarian before starting your dog on a course of supplementation.
Forms and Dosages
Vitamin E is available as a soft gel capsule for oral use and an oil for topical use. Oral vitamin E is safe for dogs provided it does not contain dog-toxic additives. Your vet will advise you on proper dosage. Working dogs, breeding dogs and dogs with high activity levels typically require more. Proper feeding requires knowing the ideal amount of food to give your dog per pound of her body weight, but this varies dramatically based on stage of life, adult size and activity level. A veterinarian or veterinary nutritionist can guide you in developing a feeding formula. Topical vitamin E oil is generally regarded as safe but is not well-studied in dogs and requires veterinary guidance.