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Certain vitamins and minerals function in the body to reduce oxidation. Oxidation is a chemical process that occurs within the body's cells. After oxidation occurs, certain by-products such as peroxides and "free radicals" accumulate. These cellular byproducts are toxic to the cells and surrounding tissue. The body removes these by-products by producing additional chemicals called antioxidants that combat these oxidizing chemicals.

In disease, excess oxidation can occur and the body's normal antioxidant abilities are overwhelmed. This is where supplying antioxidants can help. By giving your pet's body extra antioxidants, you may find it possible to neutralize the harmful by-products of cellular oxidation.

Several antioxidants can be used to supplement pets. Most commonly, the antioxidant vitamins A, C and E, and the minerals selenium, manganese and zinc are prescribed. Other antioxidants, including N-acetylcysteine, Coenzyme Q10, Gingko biloba, bilberry, grape seed extract, and pycnogenol may also be helpful for a number of disorders. There is no "correct" antioxidant to use. Dosage varies with the specific antioxidant chosen.

Following is a brief discussion of a commonly used group of antioxidants called bioflavonoids/proanthocyanidins.

Proanthocyanidins are naturally occurring polyphenolic compounds found in plants; most often products containing proanthocyanidins are made from grape seed or pine bark. Proanthocyanidins are also called pycnogenols or bioflavonoids, a class of water-soluble plant coloring agents. While they don't seem to be essential to life, it's likely that people and pets need them for optimal health. These compounds are used for their antioxidant effects against lipid (fat) peroxidation. Proanthocyanidins also inhibit the enzyme cyclooxygenase (the same enzyme inhibited by aspirin and other nonsteroidal medications); cyclooxygenase converts arachidonic acid into chemicals (leukotrienes and prostaglandins), which contribute to inflammation and allergic reactions. Proanthocyanidins also decrease histamine release from cells by inhibiting several enzymes.

Proanthocyanidins, by potentiating the immune system (via enhancement of T-lymphocyte activity and modulation of neutrophil and macrophage responses), are often recommended for use in the treatment of pets with cancer.

Some research suggests pycnogenol seems to work by enhancing the effects of another antioxidant, vitamin C. Other research suggests the bioflavonoids can work independently of other antioxidants; as is the case with many supplements, there probably is an additive effect when multiple antioxidants are combined. People taking pycnogenol often report feeling better and having more energy. This "side-effect" may possibly occur in our pets as well.

Quercetin is a natural antioxidant bioflavonoid found in red wine, grapefruit, onions, apples, black tea, and in lesser amounts, in leafy green vegetables and beans. Quercetin protects cells in the body from damage by free radicals and stabilizes collagen in blood vessels. Test-tube and animal research also suggests quercetin might be able to help prevent tumors in hamsters or enhance the effects of cancer-fighting drugs.

Quercetin appears to be quite safe. Maximum safe dosages for young children, women who are pregnant or nursing, or those with serious liver or kidney disease have not been established; similar precautions are probably warranted in pets.

In people, a typical dosage of proanthocyanidins is 200 to 400 mg three times daily. Quercetin may be better absorbed if taken on an empty stomach. The suggested dosage of proanthocyanidins complex in pets is 10 to 200 mg given daily and divided into two or three doses. The suggested dosage of bioflavonoid complex in pets is 200 to 1500 mg per day, divided into two to three doses. The actual dosage of each product will vary with the product and the pet's weight and disease condition.

Because some types of chemotherapy and radiation therapy may rely on cellular oxidation for their effects, antioxidants should not be used without veterinary supervision in pets with cancer undergoing chemotherapy or radiation therapy.


Conventional therapies for pets with cancer make use of a combination of surgery, chemotherapy, and radiation therapy.

Surgery For Pets
Surgery is the treatment of choice for solid tumors. Surgery can be curative if the entire solid tumor can be removed before it has metastasized (spread throughout the body by way of blood or lymphatic vessels). In the case of most small skin tumors, surgery is curative. When the entire tumor cannot be removed, surgery can be used to "debulk" the tumor (debulking removes as much of the tumor as possible). After debulking, additional therapy (chemotherapy or radiation) is used in an attempt to kill any remaining cells, as well as any cells that may have already spread from the original cancer site.

But does every tumor need to be removed? Of course not! Many of the pets seen for cancer consultations have benign fatty tumors, cysts, or warts that usually do not require surgical removal. With rare exception (an obvious wart), the only way to determine whether the lump is a benign lesion or a malignant cancer is through a biopsy.

Fortunately, most lumps are easily biopsied in the office with a small needle, in a procedure called aspiration cytology. In this procedure, a small needle, typically a 23 to 25-gauge needle, is gently inserted into the lump. The doctor aspirates a few cells or small amount of fluid, which are placed on a microscope slide, stained, and examined in the office.

Within minutes the doctor can usually tell whether the lump is benign or malignant. Most benign lumps grow slowly if at all and don't usually need removal. Malignant masses should be removed as soon as feasible after additional testing (x-rays, blood tests) has been done to determine if the cancer has spread.

It is vital that all lumps be biopsied! Some doctors diagnose tumors as "cysts" or "fatty tumors" by only looking or feeling the lumps; some of these in fact turn out to be malignant tumors when biopsied. The only mass that can be correctly diagnosed by visual inspection is the common papilloma or wart. All other masses, both benign lumps and cancerous tumors, look and feel the same. If your doctor says the lump doesn't need to be biopsied, get a second opinion!

Some tumors are so large by the time of diagnosis, or are in a location making surgery difficult if not impossible, that surgery is not an option. In these cases, some other form of treatment must be performed. To make the surgery as safe as possible, a thorough diagnostic workup including blood tests must be done prior to anesthesia.

Radiation For Pets
Radiation involves the use of radioactive materials, usually some type of x-ray, to kill the tumor cells. It can be used alone or in combination with surgery or chemotherapy. Radiation is not effective against every type of cancer, so it's necessary to work closely with a radiation specialist to determine which tumors are radiosensitive and are most likely to respond to this form of therapy.

Most pets tolerate radiation therapy quite well, but treatments usually require full anesthesia to administer the radiation. Common side effects of treating tumors with radiation include hair loss, burning of the skin, and discoloration of the skin. A new form of therapy for dogs with lymphosarcoma is whole body irradiation. In this procedure, the dog is anesthetized and half of the body is irradiated. Several weeks later, the procedure is repeated and the other half of the body is irradiated. The procedure has been reported to give dogs with lymphosarcoma a longer life expectancy (two to three years) than with conventional chemotherapy (12 to 18 months). The most common side effects, which last one to two weeks, are nausea, vomiting, diarrhea, and lethargy. Nutritional support and herbal therapies can be useful to minimize side effects of whole body irradiation, as well as any other radiation therapies for the pet with radiosensitive cancers.

Chemotherapy For Pets
Chemotherapy is effective against many but not all tumors. As is the case with radiation therapy, some cancers are sensitive to chemotherapy whereas others are not. Usually the goal of chemotherapy is not to cure but rather to prolong life before the cancer returns. Unlike the case with people, side effects of chemotherapy, such as vomiting and hair loss, are rare. However, pets must be monitored closely for other, more serious side effects. These side effects vary with the actual drug used, but include kidney disease, heart disease, and bone marrow suppression. Working with a knowledgeable cancer specialist is critical. Most pets do quite well with chemotherapy and suffer few side effects. Nutritional support and herbal therapies can be useful to minimize side effects of chemotherapy.

Shawn Messonnier, DVM

As my thank you for reading my articles, enter code “drshawn” at my natural products web store,, to save 10% on all your future purchases!

Shawn Messonnier DVM Past Supporting Member, Oncology Association of Naturopathic Physicians Author, the award-winning The Natural Health Bible for Dogs & Cats, The Natural Vet’s Guide to Preventing and Treating Cancer in Dogs, and Breast Choices for the Best Chances: Your Breasts, Your Life, and How YOU Can Win The Battle!

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