Neoplasia/Cardiac
Efficacy
Cancer
Research in mice with induced tumours has shown consistently that dietary fish
oil inhibits tumour growth (Hardman, 2004) and reduces the severity of cachexia
(Russell and Tisdale, 2005). The effect of fish oil is probably mediated by eicosanoids
(EPA) (Hardman, 2004) and is related to a decrease in the plasma levels of
the cytokines, tumour necrosis factor (TNF) and interleukine-1 (IL-1). Ingestion of
EPA, a polyunsaturated omega-3 fatty acid, modulates the production of eicosanoids
because it acts as a precursor. The inhibitory effect of fish oil on the development
of cachexia is related to a diminished production of tumor necrosis factoralpha
(TNF-alpha) (Tisdale, 2008). In a study with dogs, the efficacy of fish oil as
an anti-tumor agent has been shown. Dogs with lymphoma had a longer survival
time when given a diet rich in fish oil instead of soybean oil (Ogilvie et al., 2000).
Heart failure
In rats, the intake of fish oil has a specific and significant protective effect against
induced arrythmias (Matthan et al., 2005). Fish oil also has a beneficial effect in
dogs with spontaneous arrythmia. In Boxers with arrythmogenic, right ventricular
cardiomyopathy, the suppletion with fish oil reduces the arrythmia (Smith et al.,
2007).
The development of arrythmia and cachexia in patients with heart failure probably
is mediated by raised blood levels of TNF-alpha and IL-1 in the blood. A placebocontrolled study in dogs with heart failure showed that dietary fish oil lowered the plasma concentrations of TNF and IL-1 and counteracted cachexia (Freeman et al., 1998). The amount of fish oil administered was equivalent to 1.3% in a dry food.
Dogs are able to synthesize taurine, but a deficiency may develop through a
metabolic disorder in combination with low intake. Dogs are also able to synthesize
carnitine, but analogous to taurine deficiency, a carnitine deficiency can also
develop. Dogs with cardiomyopathy associated with a low carnitine concentration
in heart muscle may show improvement after carnitine supplementation (Keene et
al., 1991). In a randomised, placebo-controlled, double-blind study it was shown
that heart function and survival of dogs with cardiomyopathy and low plasma
levels of taurine had improved after supplementation of a combination of taurine
and carnitine (Kittleson et al., 1997). All patients could successfully be weaned off
medication (furosemide, ACE inhibitors, digoxine) (Kittleson et al., 1997). To treat
cardiomyopathy, the appropriate doses of taurine and L-carnitine in a dry diet appear
to be 0.15 and 0.075%, respectively.