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The Daily Vet by petMD

The Daily Vet is a blog featuring veterinarians from all walks of life. Every week they will tackle entertaining, interesting, and sometimes difficult topics in the world of animal medicine – all in the hopes that their unique insights and personal experiences will help you to understand your pets.

Low Carbohydrates

Fast growing cancer cells preferentially burn glucose to supply cellular needs. It is believed that cancer cells lack the biological pathways found in normal cells that use fats as an energy source. Theoretically a low carbohydrate diet should starve the fast growing cancer cells. Early research has been encouraging, especially for lymphoma.

This led to the development of a commercial veterinary cancer diet that provides only 14 percent of the total diet metabolic energy (ME) in the form of carbohydrate. This is significantly lower than the almost 50 percent ME from carbohydrates in most commercial foods.

One might think if less is good, than none is better, especially since carnivores have no absolute need for carbohydrates. Biologically, that is not exactly the case. The heart and brain cells of mammals are much like cancer cells. They preferentially use glucose for energy. This is why very low blood sugar can lead to weakness and seizures. In the absence of carbohydrate the liver will burn fat to produce glucose from the amino acids in proteins by a process called gluconeogenesis, or "new sugar." This process requires the destruction of muscle tissue, which turns out to be a problem for the cancer patient.

High Protein

Cancer patients, especially cats, tend to experience weight loss as their disease progresses prior to diagnosis. Much of the weight loss is a result of muscle loss. This is probably due to the competition between normal cells and cancer cells for sugar, resulting in an increased gluconeogenesis. Also, these animal are older and in various stages of geriatric sarcopenia (decreased muscle mass due to aging). High protein diets help offset these losses and keep the patients in a positive nitrogen state (derived from the fact that all amino acids contain nitrogen molecules).

There is growing evidence that the amino acids glutamine and arginine are of particular benefit to the cancer patient. Glutamine is readily used for energy in many cell types. It also serves as a reservoir for carbon and nitrogen for intracellular metabolism. It has been shown to accelerate healing after radiation therapy and to protect intestinal immunity and integrity following radiation and chemotherapy. Arginine is particularly important in immune system activity and increases antitumor immune responses. Cancer diets with 27-30 percent ME protein levels and enhanced sources of glutamine and arginine have proven beneficial to cancer patients.

High Fat

With 60-65 percent of ME coming from fat in cancer diets, they provide a rich source of energy that cannot be used by cancer cells. Higher fat diets are also more palatable to dogs and cats and can improve the appetite in these patients.

Increased levels of omega-3 fatty acids have also been shown to provide additional advantages. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) modifies the inflammatory response of the immune system to cancer activity, reducing tissue damage by decreasing certain inflammatory molecules. In addition, EPA and DHA decrease muscle and weight loss in cancer patients.

More Research

Much more research is needed to confirm the value of low carbohydrate diets, high protein, and high fat diets in pet cancer patients. So far the research is encouraging and the use of these diets is increasing. Greater usage will help evaluate their efficacy and direct future research needs.

Note: ME percentages are not found on pet food labels and differ from the percentages that are commonly found. It is a more transparent method of judging pet food but is not embraced by the pet food industry. A calculator for converting label information to approximate ME can be found here.

 

Dr. Ken Tudor

Image: M.M / via Shutterstock

Comments  13

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  • Great Info
    09/06/2012 07:28am

    Thanks, Dr. Tudor, for this information.

    If one gets a diagnosis of cancer for their critter, it's something that can hopefully retard the progression of the disease.

  • ME and pet food companies
    09/06/2012 12:37pm

    Quote: "Note: ME percentages are not found on pet food labels and differ from the percentages that are commonly found. It is a more transparent method of judging pet food but is not embraced by the pet food industry."

    You are right, Dr Tudor. This is one angle that could put paid to false claims made on pet food products and it seems the industry is fairly uniform in trying to hide the real numbers. Most people don't understand that there are 9 calories in each gram of fat, and only 4 calories for each gram of other *soluble* ingredients. Sometimes it gets pretty impossible to find the caloric count of foods, and once, when I telephoned the company for a direct answer, the one I got was basically equivalent to the protein portion in the can, not to the whole food. The company itself didn't know the caloric total.

    We fed our lymphoma boy the same food the diabetic cat was getting and not only did he go into remission, (as did the diabetic cat), he stayed there for a good five years until we caused major upheaval in his life by moving. The particular food we were using was based upon good quality protein first, and then it provided fiber, as used to be the first choice before protein came to the fore in feline diabetes foods. The fiber is insoluble and therefore doesn't become absorbed by the system and can't feed cancer cells. That also kept the fat content from being too high for our sedentary altered cat who wasn't up to much in the way of exercise through some of his chemo.

  • 09/08/2012 12:26am

    Our cat has recently been diagnosed with lymphoma. I was curious as to what diet you fed your cat. I know you mentioned a diabetic diet, but was it one of the prescription diets specifically for diabetic cats, or an off-the-shelf brand that worked for you? I would like to try switching our gal over to a food that may help slow the progression of her disease, but don't know what brands would be suitable. The nutritional info on the labels can be quite confusing.
    Any advice as to specific brands would be greatly appreciated. Thanks in advance!

  • 09/08/2012 01:19pm

    While we have always used high protein, low simple carb/fat foods, our preference here, and that of the cats, is the Royal Canin Diabetic DS 44. Any "carbs" in that are fiber.

    Before "high protein" became the buzzword for feline diabetes maintenance, veterinarians were finding success when using "high fiber" foods, because fiber IS good. It is a carbohydrate but doesn't get broken down like simple carbs, (sugars).

    I tend to think that veterinarians who aren't still leaning toward fiber content after covering the necessary protein needs just aren't using common sense based upon what they thought was best in the past -- based upon their experiences presumably. One can only guess at why "fiber" suddenly wasn't also a useful tool in pet foods. It should be great for cancer patients.

  • 09/29/2012 03:50pm

    Quote...."While we have always used high protein, low simple carb/fat foods, our preference here, and that of the cats, is the Royal Canin Diabetic DS 44. Any "carbs" in that are fiber."

    I'm confused. You are saying that corn meal gluten (yes, I realize it provides some plant-based protein), ground barley, ground corn, and brown rice are all just fiber and not carbohydrate? Is this "high protein, low simple carb"?

    Ingredients:
    ROYAL CANIN Veterinary Diet™ feline DIAbEtIC DS 44™
    Chicken meal, corn gluten meal, ground barley, soy protein isolate, ground corn, natural flavors, cellulose powder, chicken fat, brown rice, beet pulp, fish oil, vegetable oil,
    ground psyllium seed, potassium chloride, inulin, choline chloride, potassium citrate, taurine, green tea extract, sodium chloride, vitamins [DL-alpha tocopherol (source of vitamin
    E), L-ascorbyl-2-polyphosphate (source of vitamin C), niacin, biotin, riboflavin (vitamin B2), D-calcium pantothenate, pyridoxine hydrochloride (vitamin B6), thiamine mononitrate
    (vitamin B1), vitamin B12 supplement, vitamin A acetate, vitamin D3 supplement, folic acid], L-carnitine, trace minerals [zinc oxide, zinc amino acid chelate, ferrous sulfate, copper
    sulfate, copper amino acid chelate, manganous oxide, manganese amino acid chelate, sodium selenite, calcium iodate], marigold extract, preserved with natural mixed tocopherols,
    rosemary extract, and citric acid.

  • Westcoastsyrinx
    09/08/2012 06:45pm

    I am really glad that the Royal Canin product helped your pet with cancer. Certainly the high protein, low carbohydrate was helpful. Unfortunately your analysis of the food is not entirely accurate. It is approximately 45.6% ME of protein, 25% ME fat and 29% ME carbohydrate. It is only 6.8% insoluble fiber. The carbohydrates in the diet actually come from tapioca which is a soluble carbohydrate source and is readily absorbed. True "cancer diets" shoot for a much lower carbohydrate content (in the teens) with fat content in the 50-60% ME range. Royal Canin does not list a cancer diet so I don't know if they have or are working on an equivalent to the Hill's n/d cancer diet. Purina and Iams do not list any veterinary cancer diets. Certainly some of the raw and homemade diets that emphasize protein and fat with tiny portions of carbohydrates could be formulated for great cancer diets as long as they were properly analyzed and balanced with calcium, phosphorus, vitamins and minerals.
    Dr. T

  • 09/08/2012 07:41pm

    "The carbohydrates in the diet actually come from tapioca which is a soluble carbohydrate source and is readily absorbed."

    To be accurate, Dr Tudor, exactly 3.3 grams of every 100 grams of tapioca are "sugars": http://nutritiondata.self.com/facts/cereal-grains-and-pasta/5733/2 The highest quote I have been able to find online in order to have an unbiased assessment has been 23%, or 23 grams per 100, but I find that as a person trained in human nutrition, the URL I used above is the best source for gauging the quality of a food based upon ingredients. Other portions of tapioca are more complex, and my personal choice is to avoid celiac issue grains, so right or wrong, I am happy with the selection that keeps our pets out of the need for more than yearly checkups and a clean bill of health.

    As I stated before, we did give our lymphoma patient remission and five very good years of life on the RC diet, and we didn't have to provide the prednisone "maintenance" recommended by veterinarians to do it: http://maxandrenallymphosarcoma.blogspot.ca/ The food also kept our diabetic boy in remission for over a decade until his very old body started breaking down after a stressful move and loss of his best buddy, the cancer patient.

    There is no "perfect" food, and I was asked to clarify what we had used in our home.

  • 09/08/2012 07:45pm

    I should perhaps qualify that I don't much trust the labelling on packaging because I have found manufacturers to be grossly incorrect, particularly when it comes to caloric count, which is your area of expertise, Dr Tudor.

  • Naturally...
    09/09/2012 12:17am

    "Much more research is needed to confirm the value of low carbohydrate diets, high protein, and high fat diets in pet cancer patients. So far the research is encouraging and the use of these diets is increasing. Greater usage will help evaluate their efficacy and direct future research needs."

    You bet the use of these diets is increasing! The closer the diet to a pet's physiological needs, the more efficiently and easily it is for that pet's digestive system to process the food and obtain the nutrients required to thrive. The body - and the immune system - are stronger for the additional nutrition, and the ease of digestion reduces stress upon the GI tract and allows inflammation to subside and healing to begin.

    As far as the discussion on gluconeogenesis, Dr. Peterson, a well-known endocrinologist, explains how cats are built to use protein - not carbs - for their energy needs. They are so specifically engineered for preferential use of protein, they will sabotage their own bodies for what they need to survive if their diet doesn't contain enough, *completely irrespective of the amounts of carbohydrates present in that diet*. (http://endocrinevet.blogspot.com/2011/11/optimal-protein-requirements-for-older.html and http://endocrinevet.blogspot.com/2011/12/can-increasing-amount-of-fat-or.html)

    I'm delighted to see more discussion on the benefits of feeding our pets foods that are more aligned with their species-specific needs!

  • westcoastsyrinx
    09/09/2012 01:47pm

    You are absolutely right. There is no perfect food. I find the idea of using diabetic formulas in treating cancer patients very insightful. I have not read any studies that have compared their use in cancer to other cancer diets but if you have some citations I would be very interested. Since there is no Rosetta Stone for nutrition, I think it is important that we try and be as factual as possible when trying to help others. Without sounding too petty, your discussion of the digestibility of tapioca is interesting but calculations indicate that there is enough tapioca and or other carb sources in the diet that almost 1/3 of the digestible calories are derived from carbohydrates. That is a far cry from "Any carbs in that are fiber." The diet worked for your cat and you wanted to help a fellow reader with their cat. I get that, but as a fellow scientist I am sure that you agree that being more objective offers more useful information to help others make decisions. That was my only point. It is indeed low carb by industry standards but it is not no carb.
    Dr. T

  • 09/10/2012 03:19pm

    Hi Dr Tudor; If you take one ingredient in the list of the food we are using as an example, such as corn gluten meal: http://www.ingredients101.com/cgm.htm, you can start to see that the guaranteed analysis on pet foods is not the best guide to a particular product. The companies producing the final product are taking their numbers from their suppliers, who use data such as that provided by Ingredients 101 to come up with content. A very hap hazard process indeed, and when I have gone to the trouble of breaking a food down, gram by gram, I find the analysis can be quite inaccurate, as I hinted before with personal experience checking caloric count.

    To get back to your tapioca, for a moment, the chances are it would be in the form of a cassava pulp as that is what usually goes into animal feed, (not clarified on packaging), and an example of how much better this is than potato or other ingredients as a substrate for good gut bacteria is here: http://journal.ui.ac.id/technology/article/viewFile/938/872

    One of the few products on the market that can spike glucose levels in diabetic cats, (according to owner reports when doing curves), is one that claims, "no carbs". The product contains fructose in the fruits and vegetables which is a simple sugar, (aka "carb"), that can be absorbed through membranes in the mouth, which is why it is used to pull diabetics out of hypoglymic episodes, (eg, corn syrup). Considering cats don't normally have post prandial spikes, (http://www.ncbi.nlm.nih.gov/pubmed/11714241), only the simplest of carbohydrates, that CAN bypass the digestive system, could accomplish this. And no, I don't have immediate proof of this but if you are treating diabetes along with obesity, I am sure you could oberve the problems such owners have for yourself when cats are fed foods with fruits and vegetables rather than *listed* complex carbohydrates.

    The Royal Canin product we have been discussing, might be slighly different in the US to what we have in Canada, but ours states right up ahead of the ingredient list in bold writing, "low starch". The tapioca is also contributing to calcium intake, etc., with its content. You have "powdered cellulose," "dried chicory root," and "psyllium seed husk," let alone the variety of fermentable fibers such as the "Neutral Detergent Fiber" and "Acid Detergent Fiber" that are in the corn gluten meal that is given such a bad rap by extremists. I would be far more concerned with bioavailability of secondary nutrients that might be hampered by so much fiber: https://www.ideals.illinois.edu/handle/2142/19371 for an example.

    My training is very different from that provided in veterinary schools and was very focused upon glycemic control of humans, with recent research and updates regarding our pets done after my retirement for personal use. Two veterinarians who have been a substantial help in my ability to meld the past training with present interests have very opposite views in some areas, (eg free feed vs timed feedings), so it doesn't surprise me one bit that we may disagree on some particulars. Even the FDA can't decide on what figures should constitute, "low" or "high" content of any nutrient, so how can the rest of us show any conformity?

    Hopefully those of us who have common interests such as pet obesity and diabetes can come to some sort of agreement. (-:

  • 09/10/2012 05:06pm

    Perhaps it would help those who just want the facts to understand that tapioca, in its starchiest form, is about the same as guar gum, but has less irritating side effects:

    Guar gum: http://www.isca.in/IJBS/Archive/v1i1/10.ISCA-JBS-2012-001.pdf

    Tapioca: http://www.academicjournals.org/ajfs/pdf/Pdf2008/Jul/Adebowale%20et%20al.pdf

    From what I can tell, that is the worst case scenario as tapioca as a "feed" ingredient usually has the starch removed. Guar gum is an irritant for humans with IBS, so I would prefer to take my chances with something listed as tapioca that has the opposite effect. Could be because guar gum comes from beans and tapioca comes from tubers - just a guess.

    HTH.....

  • Dogs and Mushrooms?
    09/11/2012 08:04pm

    What is your opinion on this, Dr Tudor?

    http://www.eurekalert.org/pub_releases/2012-09/uop-mcl091012.php Quote: "Mushroom-derived compound lengthens survival in dogs with cancer, Penn Vet study finds".

    Perhaps if you are creating home made recipes they should include mushrooms for cancer patients?

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