Canine Heart Disease and Nutrition: Part 2
Reducing salt intake with heart disease has been a mainstay of medical management of heart disease in humans. Increased sodium in the diet causes increases levels of sodium circulating in the blood. These elevated levels of sodium cause water retention in the blood vessels and elevated blood pressure. As blood pressure increases the diseased heart must continue to enlarge to overcome the increased pressure in order to pump blood from the ventricles. As we discussed, unnecessary cardiac enlargement leads to eventual congestive heart failure. Reducing sodium in the diet slows this enlargement. The same favorable effects have been documented in dogs. Moderate sodium intake reduces cardiac enlargement.
Potassium and Magnesium Supplementation or Restriction
Many of the medications used to treat heart disease decrease blood levels of potassium and magnesium. Inadequate levels of potassium and magnesium can promote heart arrhythmias and weaker heart muscle contractions. Both situations decrease blood flow to the rest of the body organs. Other medications cause the retention of excessive levels of potassium. This hyperkalemia can also disrupt cardiac rhythm and blood flow. Frequent monitoring of these electrolytes is important in cardiac patients.
Many pet owners are aware of the dietary need for the amino acid, taurine, in the cat diet and the heart problems associated with taurine deficiency. Less known is that studies in Cocker Spaniel, Newfoundland, Portuguese Water dogs and Golden Retrievers have shown an association with dilated cardiomyopathy (DCM) and taurine deficiency. Although taurine supplementation experiments in dogs with DCM have not shown the same positive results found in cats with DCM there is much research activity in this area. Very low protein diets, some lamb meal and rice diets, vegetarian diets, and high fiber diets are taurine deficient and should probably be avoided in DCM patients unless properly supplemented.
EPA and DHA Fatty Acids
The omega-3 fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are known to help to reduce inflammation. In humans these fatty acids can reduce arrhythmias by more than 70 percent within 24 hours after consuming fish oil. Studies in boxers and other breeds have also shown positive results with fish oil. Flaxseed oil, another omega-3 containing fat, has not shown the same positive effects. The inefficiency of the conversion of omega-3’s to EPA and DHA in the liver is cited for the difference. The EPA and DHA in fish oil is preformed and needs no conversion from other omega-3s in the oil.
As congestive heart failure progresses, heart cell damage increases from the formation of “free radicals” (reactive oxygen molecules created during oxygen metabolism). Studies in dogs with congestive heart failure have shown that these patients have increased reactive oxidants and decreased antioxidants as the disease progresses. The use of Vitamin C and E in in the treatment of these patients has recently increased.
Arginine is an essential amino acid that reacts with oxygen to produce nitric oxide. Nitric oxide relaxes the smooth muscles of blood vessels and reduces blood pressure. Human patients with congestive heart failure have lower levels of vascular nitric oxide and suffer increased exercise intolerance and decreased quality of life due to vascular dysfunction. Arginine supplementation improves vascular function and benefits these patients. Studies are underway in dogs.
L-Carnitine is a vitamin-like chemical synthesized in the cell from the amino acids, lysine and methionine. L-Carnitine aids in energy production in the cell, especially the muscle cells of the heart. L-Carnitine deficiency has been associated with heart disease in humans and dogs. It is not known if this is a causative association. Supplementation studies in dogs are suggestive, but not yet conclusive.
In addition to aiding energy production in heart cells, Coenzyme Q10 is an antioxidant. It is thought that this combination of activity may help in congestive heart failure to aid heart cell strength and prevent oxidative cell damage. The studies are conflicting so definitive evidence that Coenzyme Q10 is helpful in heart patients is lacking.
Consult your veterinarian about the use of any these supplements.
Dr. Ken Tudor