Antioxidants are natural compounds that are important in the neutralization or scavenging of “oxygen free radicals,” which are normal by-products of body metabolism. Controlled amounts of free radicals are normally made by the body as weapons against viruses and bacteria, and are used in hormone production and numerous cellular reactions.

However, excess free radicals can damage cellular DNA, destroy cell membranes, and lead to chronic inflammation, degenerative diseases, immune system damage, and even cancer.

Excessive amounts of free radicals can result from exposure to radiation, including sunlight, environmental pollution, and unhealthy diets. In people, a diet high in fresh fruits and vegetables may contain adequate natural antioxidants. Pets eating commercial food, however, do not get enough appropriate antioxidants in the diet.

Since free radical formation is a normal process, it’s no surprise that the body has a natural defense system against them: antioxidants, which scavenge and dismantle those radicals. Plants also make many antioxidants that are helpful to humans and animals. Vitamins C and E are probably the best-known plant antioxidants.

Specific Antioxidants and Dosing Information

There are many good antioxidant supplements on the market. Where dosage information is not specified, give a cat from 1/10 to 1/6 the human dosage, as indicated on the label. (A human dose is calculated for a 150-lb. person.) Research has shown that it is more effective to give antioxidants in combination than to give single antioxidants alone. Here are some specific antioxidants that may be helpful in cats:

Omega-3 fatty acids have excellent antioxidant, anti-inflammatory properties. Click here for more info.

Vitamin C is a powerful antioxidant and has many other important functions. Cats can make their own vitamin C, but in many cases it doesn’t seem to be enough to cope with the stresses of modern living. Avoid supplements that contain only ascorbic acid, which is usually synthetically produced. Use sodium ascorbate, calcium ascorbate or “Ester C” – they’re less likely to cause tummy upset. Vitamin C may be dosed to “bowel tolerance.” That is, you start off adding just a little Vitamin C (50-100 mg) to the food, and increase the dose very gradually until the animal develops diarrhea. At that point, you back off to the previous dosage amount that did not cause diarrhea, and stay with that dose. An individual pet’s tolerance may vary, depending on diet, time of year, and stresses such as changes in the home, pollution and exposure to radiation (UV light, X-rays, power lines, etc.). In general, 100 mg per day is plenty for a cat. To increase the efficacy of Vitamin C, take it with rutin and/or quercitin, which are also flavonoid antioxidants.

Vitamin E’s natural form is d-alpha-tocopherol. Avoid synthetic Vitamin E, dl-alpha-tocopherol. If the label says just “alpha,” it’s probably the synthetic (cheaper) kind. While alpha-tocopherols are more common, a product containing “mixed” tocopherols may have more benefits. A cat should get 50-100 IU per day. Vitamin E should be added to the diet whenever you are supplementing with oils, such as fish oil, that do not already have Vitamin E added.

Vitamin A/beta-carotene. Most mammals, including dogs, can use beta-carotene to make Vitamin A, but cats cannot convert it and must receive Vitamin A itself in the diet. Cats do absorb beta-carotene, which has other metabolic uses, but it cannot be used as a substitute for Vitamin A. CAUTION: Vitamin A (though not beta-carotene) can be toxic in overdose. Signs of toxicity include anorexia, weight loss, sensitivity to touch and loss of bone density, which may cause fractures. Kittens require about 200 IU of Vitamin A per kilogram of body weight per day; adult cats about 75 IU per kilogram per day. Commercial pet foods contain adequate amounts of Vitamin A for cats and no additional supplements should be used.

MSM (methyl-sulfonyl-methane), a derivative of DMSO, may help the body maintain adequate levels of cysteine in the body. Start with 200 mg per 10 lbs. body weight daily, increase gradually until symptoms resolve.

Proanthocyanadins (pycnogenol/pine bark extract and grape seed extract) are highly concentrated antioxidants that are easy and fairly inexpensive to use.

Zeaxanthin & Lutein. These antioxidants are often found together in nature; they are especially important for eye health.

Astaxanthin. Made by certain algae, this “new kid on the block” may be helpful for several conditions in humans; research in animals, however, is lacking.

Chlorophyll, the plant version of heme, the oxygen-carrying molecule in hemoglobin, contains fat-soluble vitamins, minerals, amino acids and other valuable nutrients, and appears to have antioxidant activity. It’s available as a liquid extract and capsules, and can be found in products like BioSuperfood and even cat treats.

Resveratrol. This antioxidant is found in grapes, grape skins, and grape seed extracts. It is important to know the source, as grapes and raisins may produce toxic kidney failure in dogs. Because the exact toxic factor in grapes is unknown, resveratrol should be used with caution (if at all) in pets.

Co-enzyme Q10 (Ubiquinone). While not specifically a free radical scavenger, Co-enyzme Q10 helps prevent the formation of oxygen free radicals during cellular metabolism–a sort of “pre-antioxidant.” This enzyme is present in every cell in the body, but its levels decrease as we age. It has been shown to improve oxygenation to the heart, and may be beneficial in chronic inflammatory conditions such as cystitis and arthritis. Older cats and those with inflammatory disease may benefit from supplementation. The average cat may take 5-10 mg a day.

**Warning** The popular antioxidant for people, alpha-lipoic acid, is fine for dogs, but toxic to cats. Avoid it, or at least limit it to no more than 15 mg per day.



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