ANTIOXIDANTS FOR PETS
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
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
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.