Cancer in Cats and Dogs Part 3 Omega-3 Fatty Acids

Omega-3 Fatty Acids

Omega-3 fatty acids-eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)-are derived from fish oils of cold water fish (salmon, trout, or most commonly menhaden fish) and flaxseed. Omega-6 fatty acids-linoleic acid (LA) and gamma-linolenic acid (GLA)-are derived from the oils of seeds such as evening primrose, black currant, and borage. Often, fatty acids are added to the diet with other supplements to attain an additive effect.

In transplanted tumor models, omega-3 fatty acids reduced tumor development while omega-6 fatty acids stimulated tumor development. Omega-3 fatty acids have been shown to inhibit tumor growth as well as the spread of cancer. Reduced radiation damage in the skin was also seen following supplementation with omega-3 fatty acids.

The use of omega-3 fatty acids can promote weight gain and may have anticancer effects, and warrants special mention. In people, the use of omega-3 fatty acids, such as those found in fish oils, improves the immune status, metabolic status, and clinical outcomes of cancer patients. These supplements also decrease the duration of hospitalization and complication rates in people with gastrointestinal cancer. In animal models, the omega-3s inhibit the formation of tumors and metastasis. Finally, omega-3 supplementation shows anticachetic (anti-wasting) effects.

Note: Flaxseed oil is a popular source of alpha-linoleic acid (ALA), and omega-3 that is ultimately converted to EPA and DHA. However, many species of pets (probably including dogs) cannot convert ALA to these other more active non-inflammatory omega-3s. Also, flaxseed oil contains omega-6, which are not recommended in pets with cancer. In one study in people, flaxseed oil was ineffective in reducing symptoms or raising levels of EPA and DHA. While flaxseed oil has been suggested as a less smelly substitute for fish oil, there is no evidence that it is effective when used for the same therapeutic purposes as fish oil. Therefore, supplementation with EPA and DHA is important, and this is the reason flaxseed oil is not recommended as the sole fatty acid supplement for pets.

While many doctors use fatty acids for a variety of medical problems, there is considerable debate about the use of fatty acids. The debate concerns several areas.

Dosages
What is the "best" dose to use in the treatment of pets? Most doctors use anywhere from two to ten times the label dose. The recommended dosage for pets with cancer is approximately 1500 mg/100 kcal of food. In order to get this dose, depending upon the product selected, you would need to feed your dog about five capsules per 100 kcal of diet. This is a LOT of fatty acid capsules!

Is supplementation with fatty acid capsules or liquids the best approach, or is dietary manipulation preferred for treatment of cancer? There is one diet, Prescription Diet n/d, made for dogs with cancer. This diet contains the "proper" amount of omega-3 fatty acids, and it is impossible to add enough fatty acids in the form of supplements to equal the amount found in this diet. However, the protein source, beef lung, is not the most wholesome protein source, which is a concern for holistic pet owners. Many owners use some of the n/d with a homemade diet plus additional fatty acids to achieve a compromise.

Studies done in dogs with lymphoma and nasal tumors have shown that dogs eating the n/d showed increased disease-free intervals and survival times when compared with similarly treated dogs not eating this diet. While research has not been reported in dogs with other cancers or in cats with cancers, it is recommended to use fatty acid supplementation in pets with any kind of cancer due to the potential benefit.

Fish Oils For Pets

Since fish oils can easily oxidize and become rancid, some manufacturers add vitamin E to fish oil capsules and liquid products to keep the oil from spoiling. (Others remove oxygen from the capsule.)

The bottom line is there are many questions regarding the use of fatty acid therapy. More research is needed, as well as the proper dosage needed to achieve clinical results. Until definitive answers are obtained, you will need to work with your doctors to determine the use of these supplements for your pet.

Fish oil appears to be safe. The most common side effect is a fish odor to the breath or the skin.

Because fish oil has a mild "blood-thinning" effect, it should not be combined with powerful blood-thinning medications, such as Coumadin (warfarin) or Heparin, except on a veterinarian's advice. Fish oil does not seem to cause bleeding problems when it is taken by itself at commonly recommended dosages. Also, it does not appear to raise blood sugar levels in people or pets with diabetes.

Flaxseed Oil For Pets

Flaxseed oil is derived from the seeds of the flax plant and has been proposed as a less smelling alternative to fish oil. Flaxseed oil contains alpha-linolenic acid (ALA), an omega-3 fatty acid that is ultimately converted to EPA and DHA. In fact, flaxseed oil contains higher levels of omega-3 fatty acids (ALA) than fish oil. It also contains omega-6 fatty acids.

As mentioned, many species of pets (probably including dogs and cats) cannot convert ALA to these other more active non-inflammatory omega-3 fatty acids. In one study in people, flaxseed oil was ineffective in reducing symptoms or raising levels of EPA and DHA. While flaxseed oil has been suggested as a substitute for fish oil, there is no evidence that it is effective when used for the same therapeutic purposes as fish oil. Unlike the case for fish oil, there is little evidence that flaxseed oil is effective for any specific therapeutic purpose.

Therefore, supplementation with EPA and DHA is important, and this is the reason flaxseed oil is not recommended as the sole fatty acid supplement for pets. Flaxseed oil can be used to provide ALA and as a coat conditioner.

Flaxseed oil also contains lignans, which are currently being studied for use in preventing cancer in people. To date, we have no information to recommend their use in pets with cancer.

The essential fatty acids in flax can be damaged by exposure to heat, light, and oxygen. For this reason, you shouldn't cook with flaxseed oil. A good product should be sold in an opaque container, and the manufacturing process should keep the temperature under 100 degrees F. Some manufacturers combine the product with vitamin E because it helps prevent rancidity.

The best use of flaxseed oil is as a general nutritional supplement to provide essential fatty acids. It appears to be a safe nutritional supplement when used as recommended.

Glycoproteins
Glycoproteins are protein molecules bound to carbohydrate molecules. Glycoprotein molecules coat the surface of every cell with a nucleus in the human body. The body uses the glycoproteins on cell surface glycoconjugates as communication or recognition molecules. These communications may then result in other cellular events, including secretion of bioactive substances (interferon, interleukin-1, complement), ingestion of bacteria and cell debris, inhibition of adherence necessary for bacterial infection, and the spread of cancer cell metastasis.

Scientists have identified eight sugars, glycoforms, found on human cell surfaces that are involved in cellular recognition processes. Of the 200 such sugars occurring naturally in plants, to date only these eight have been identified as components of cellular glycoproteins. These eight sugars that are essential for glycoconjugate synthesis (mannose, galactose, fucose, xylose, glucose, sialic acid, N-acetylglucosamine, N-acetylgalactosamine) can be readily absorbed and directly incorporated into glycoproteins and glycolipids.

Research has found specific cell surface glycoforms to be characteristic of many disease conditions. In some people with rheumatoid arthritis, some of these patients' defense cells (IgG antibody) bear malformed glycoproteins. These cells are missing required galactose molecules; the extent to which the galactose molecules are missing correlates with disease severity and reverses in disease remission. In people with cancer, more than 20 different malignancies are known to be associated with characteristic glycoproteins.

Glyconutritional supplements are designed to provide substrates for the body to use in building part of the glycoconjugates on cell surfaces. These supplements, most commonly acemannan and mannose, are designed to make the necessary sugars available to the cells quicker and in greater quantity.

Acemannan is a glycoprotein (a long chain of mannan polymers with random o-acetyl groups) derived from the aloe vera plant that has been shown to increase the body's production of immune-modulating chemicals, including interleukins 1 and 6, and Prostaglandin E2 and tumor necrosis factor alpha by macrophages. Acemannan also enhances macrophage phagocytosis and nonspecific cytotoxicity, which increases the ability of white blood cells (macrophages) to destroy infectious organisms. Glycoproteins such as acemannan also offer antiviral activity as well as bone marrow stimulating activity.

Scientific Evidence
Acemannan has been approved as an adjunct therapy for solid tumors called fibrosarcomas. Intralesional injection into the tumor (2 mg weekly for up to six weeks), combined with intraperitoneal injections (1 mg/kg of body weight given weekly for six weeks, followed by monthly injections for one year), has been shown to be effective in shrinking tumors (via necrosis and inflammation).

All eight of the glycoconjugate sugars are readily absorbed from the intestines when taken orally. Studies has shown intact mannose molecules are rapidly absorbed from the intestine of rats into the blood, elevate the blood mannose levels by 3-to 10-fold, and is cleared from the blood within hours. The conclusion reached was that mannose was absorbed from the intestinal tract into the blood and from the blood into the cells. These studies suggest that dietary mannose may make a significant contribution to glycoforms synthesis in mammals.

Other human and animal ingestion studies show mannose is readily absorbed, and is cleared from the blood over several hours; some of the mannose was incorporated into glycoproteins. After absorption into the blood, glycoconjugate sugars generally become distributed (usually as glycoproteins and glycolipids) into body fluids, organs, and various body tissues.

In one study, healthy humans were given radiolabeled galactose, mannose, or glucose. This study showed galactose and mannose were directly incorporated into human glycoproteins without first being broken down into glucose. The conclusion was specific dietary sugars could represent a new class of nutrients and the use of these nutrients could have important consequences. Therapy with mannose offers a treatment that is easy to administer and is nontoxic.

Most of the essential glycoconjugate sugars have demonstrated an ability to inhibit cancer growth and the spread of tumor cells both in vitro and in vivo (in experiments in pets and people). The ability of the glycoproteins to inhibit tumor growth may be related to their ability to alter the activities of the immune system. Glycoconjugate sugars stimulate white blood cells (macrophages), which secrete interferons. The interferons activate natural killer cells that help eliminate cancer cells. The glycoproteins may inhibit the spread of tumor cells by preventing them from adhering to each other as a result of competitive inhibition of glycoconjugate receptor binding.

Adverse effects caused by glycoconjugate sugars are rare and usually occur when they are injected or when doses greatly exceed levels that would be expected in normal diets. For pets being treated with the most commonly used glycoproteins (acemannan and mannose), side effects would not be expected.

The final part of our cancer in pets series concludes next month. We will discuss the use of antioxidants, and conventional therapies such as surgery, radiation and chemotherapy.

Cancer in Pets