Cancer. It’s about the scariest word a pet owner can hear.
There are many different types of cancers. Some cancers will have tumours and others are cancers of the blood that do not have visible growths. Not all tumours are malignant; some are benign and are simply a tumour that can be surgically removed and your dog will recover fully. Other types of cancer are more insidious and cannot easily be treated. Fortunately, there are now treatment options for most canine cancers and those treatments are improving all the time. Thirty years ago, we never would have considered that a dog could survive a cancer diagnosis. Now, we are faced with the challenges of supporting a dog both during and after treatment.
As a dog owner, one vital thing you can do is to feed a diet (homemade or commercial) that will provide your dog with the nutritional weapons needed to fight the cancer. The research on exactly what should be fed and what supplements work best is still being conducted, however, we can give some guidelines on what foods may be helpful for dogs fighting cancer.
Feeding the Dog with Cancer
Many dogs with cancer are affected by cancer cachexia. Cachexia is a metabolic condition during which the dog experiences weight loss, loss of appetite, fatigue, and impaired immune function.
Cancer cachexia has three phases. In the first phase, there are nonvisible, biochemical changes in the dog’s body. In the second phase, there are clinical signs (weight loss, anorexia, etc.), and in the third phase, there is a severe loss of body fat and muscle mass, which results in debilitating lethargy. Cachexia is a huge challenge in treating dogs with cancer because in some cases it is actually the cause of death, not the cancer itself. Cancer cachexia causes a change in the way the dog’s body metabolises carbohydrates, proteins, and fats. These changes result in poor use of energy by the dog, and increased energy use by the cancer.
Tumour cells get their energy from glucose in the bloodstream of the dog. The tumour metabolizes this glucose for energy and it creates lactate as a by-product. The dog’s body must then convert this excess lactate back into glucose. Unfortunately, this is not an efficient system, so the dog ends up using more energy than it is making. Simple carbohydrates (like pasta or bread) are the source of glucose that the tumour uses. In order to minimize the energy available to the tumour, it is important to limit and carefully select carbohydrate sources so that we feed the dog and not the tumour. Look for foods with a low glycemic index. Lower-glucose carbohydrates include fruit (i.e., apples, berries, bananas), honey, peas, oatmeal, and brown rice.
Both the dog and the tumour need protein. As the dog’s body tries to meet its need for protein, the tumour will attempt to meet its need for protein, as well. This results in a decrease in the amount of protein that is available for maintaining muscle mass in the dog and an increase in protein being made by the liver. This protein deficit leads to muscle wasting, poor immunity, and delayed wound healing. To ensure the dog has enough building blocks to make muscle and other proteins, we need to feed a food with a high percentage of the calories coming from good-quality protein.
Much of the weight loss in dogs with cancer cachexia is from a loss of body fat. Dogs with cachexia have a reduced appetite and so they don’t eat as much. There are changes in the dog’s metabolism that cause a decrease in the production of new fat, consequently their body will start to use up the fat stores. The loss of fat stores is a poor prognosis for any animal with cancer. Fat stores allow the body to survive short term fasts when the dog is not feeling well. Adding the right types of fat, such as omega fatty acids, to the diet can help prevent cancer cachexia.
A walk down the supplement aisle in your local pet store will probably leave you feeling a bit bewildered. There are a lot of choices out there, and many make promises that seem too good to be true. Unfortunately, there are no supplements that will cure cancer but there has been research into some which may help limit tumour growth.
A number of studies have demonstrated that the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA) may prevent the growth and development of some tumours and may help to prevent cancer cachexia. They also improve the immune system. These fatty acids are found in fish oils.
Vitamin D has been shown experimentally to inhibit cell growth, promote cell death, and cause cell differentiation. These are all important in the prevention of cancer. Vitamin D has been shown to prevent colorectal neoplasia (unwanted cell growth). There is less clear data to show that Vitamin D is effective against all cancer types, but it does have potential. Vitamin D is a fat soluble vitamin and it is possible to feed too much and cause a toxic effect. Dogs should not get more than 10,000 IU per kilogram of food.
CLA is a naturally occurring fat found in dairy products such as butter and full-fat milk or cream. It has been shown in rodent studies to help prevent cancer growth. Supplementation in one dog with mammary cancer (breast cancer) has shown promising results; however, it has not been widely used in dogs.
Green tea polyphenols such as EGCG have been shown to have an anticancer effect. Many studies have shown that EGCG may enhance the body’s ability to prevent cancer. It has the ability to cause cancer cell suicide (apoptosis). The two main challenges that we have with EGCG is that it has a very short half-life in the body so you have to drink a lot of it, and it doesn’t work in all animals or people. There are no studies showing the effect of EGCG in dogs with cancer. However, most scientists agree that it is unlikely to cause harm and it may help.
The best dose of green tea for dogs is unknown. Studies have shown that a dose of 2000mg/kg (i.e., 60g/day for a Labrador) of EGCG was lethal in rats. In other studies with dogs, a dose of 500 mg EGCG preparation/kg was given to dogs after a meal in a divided dose caused no adverse reactions. This same dose caused the dogs to be sick when it was administered to fasted dogs as a single bolus dose. So the maximum dose you should feed your dog is 500mg/kg and it should be fed on a full stomach. An important note about EGCG is that it can interfere with some chemotherapy drugs, so discuss using this with your veterinarian before you feed it to your dog undergoing cancer treatment.
How to Pick a Food for your Dog with Cancer
When choosing a food for your dog with cancer, you want to pick something that is highly palatable and has lots of kcal/cup of food. A sick dog doesn't need to eat as much in order to meet its energy needs. Look for a diet where 30-50 percent of the calories come from a good quality protein source, 50-60 percent of the calories come from fat, and the rest of the calories come from carbohydrates. There are commercially prepared foods available for dogs on cancer treatment but you will need to ask your veterinarian to order them for you.
You may also want to add some supplements to your dog's diet. It is important to discuss these with the vet who is treating your dog's cancer to ensure there aren't any interactions with any of the medications or treatments. Your dog may also need a few more calories than they normally do, so keep a careful eye on their weight.
There is no way to prevent cancer entirely, but one of the risk factors that you can control is your dog's weight. Multiple studies have shown that dogs that are obese have an increased risk of developing cancer. Aim to keep your dog at a body condition score of 2.5/5 or 4.5/9. Keeping your dog's paws out of the cookie jar and keeping him or her fit can help them to lead a longer, healthier life.