Fish oil decreases natural resistance of mice to infection with Salmonella typhimurium.

Mortality rate in mice fed fish oil for 4 weeks was remarkably higher after a very low peroral (PO) challenge with Salmonella typhimurium, as compared with those fed diets rich in either corn oil or hydrogenated coconut oil, or a low fat (chow) diet. None of the surviving mice fed the fish oil diet showed bacterial counts in their spleens, unlike 45.4% to 66.6% of surviving mice fed high fat or low fat diets. The spleens of mice fed fish oil presented the highest number of bacteria 7 days after intraperitoneal infection with the same bacterial strain. Thus, the current studies demonstrate that a diet rich in fish oil decreases host resistance to infection.