Protein-energy malnutrition is associated with cardiac atrophy and adaptive reduction in cardiac output.Refeeding increases cardiac output and oxygen consumption. Rapid refeeding of severely malnourished patients can precipitate heart failure. Micronutrient deficiencies also contribute to cardiac dysfunction. Cardiac failure can cause weight loss and malnutrition. The most extreme degrees of cardiac malnutrition occur in patients with right heart failure and tricuspid incompetence. These patients have increased mortality but feeding protein and energy does not improve cardiac function. The hearts in patients with cardiac failure have mitochondrial dysfunction and these mitochondria are depleted of carnitine, coenzyme Q10 and taurine. The severity of depletion is related to the severity of heart failure. In controlled trials, repletion of carnitine and coenzyme Q10 improves outcome. Furthermore, in heart failure oxidative stress is increased and there may be thiamin deficiency. It is proposed that the nutritional therapy of heart failure should be directed to the replacement of carnitine, coenzyme Q10 and taurine as well as antioxidants and thiamin rather than protein-energy.