Beef jerky, salami, hot dogs and other cured meats could contribute to manic episodes, scientists have said.
An analysis of more than 1,000 people with and without psychiatric disorders has shown that nitrates – which are chemicals used to preserve meats and other processed snacks – are linked to abnormal mood states.
The research, which was carried out by Johns Hopkins University School of Medicine in the US, found that people who were admitted to hospital for an episode of mania – which is characterised by hyperactivity, euphoria and insomnia – were three times more likely to have eaten nitrate-cured meats than people without a history of a serious psychiatric disorder.
Experiments on rats showed similar mania-like hyperactivity after just a few weeks on diets with added nitrates.
The researchers said that their study adds to evidence that certain foods, combined with certain types of gut bacteria, could contribute to mania and other disorders which affect the brain.
Lead author Robert Yolken, of the Johns Hopkins University School of Medicine, said: “We looked at a number of different dietary exposures and cured meat really stood out.
“Future work on this association could lead to dietary interventions to help reduce the risk of manic episodes in those who have bipolar disorder or who are otherwise vulnerable to mania.”
Mania is generally seen in people with mood disorders such as bipolar disorder or schizoaffective disorder.
Manic states can lead to dangerous risk-taking behaviour and can include delusional thinking.
The team said further research is needed to understand the mechanism by which nitrates increases the risk of mania, but tests on rats showed that rodents which ate nitrate-added jerky displayed irregular sleeping patterns and hyperactivity compared with those which did not.
When the group analysed the gut bacteria of the rats, they found that animals with nitrate in their diet had different patterns of bacteria living in their intestines compared with other rodents.
The animals also “had differences in several molecular pathways in the brain that have been previously implicated in bipolar disorder”, the researchers added.
The team said it is too early to take any clinical messages from the results, adding that occasional cured meat consumption is unlikely to spur a manic episode in most of the population and that further research is needed to understand the association.
The findings are published in the journal Molecular Psychiatry.
