After only a few weeks, the rats began to show signs of hyperactivity, while the rats that were not fed the nitrates showed no changes, according Johns Hopkins.
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The study authors found further specific insights: Recently consuming meat sticks like Slim Jims, beef jerky, or turkey jerky increased the odds of being in the mania group.
While occasional cured meat consumption is unlikely to spur a manic episode in most of the population, Yolken says the findings add to evidence that multiple factors contribute to mania and bipolar disorder.
Yolken was originally interested in studying the effect foods may have on mental illness, and conducted a demographic study of 1,101 people both with and without mental disorders. Between 2007 and 2017, researchers at the nearby Sheppard Pratt Health System asked 758 willing psychiatric patients to fill out comprehensive lifestyle questionnaires as part of a separate project.
The main inclusion criterion for participants with mania was current admission to hospital for symptoms of mania or hypomania.More news: A law that divides and discriminates
Taylor is now running a study which involves flushing out the gut bacteria of people with bipolar disorder and giving them fecal transplants from people known to be in good mental health, to see if it can lead to lesser symptoms and improved conditions.
The researchers believe that this is because these type of foods contain the chemical nitrate, which is used to help preserve them.
But by delving into a decade's worth of data, the researchers were surprised to find those hospitalized with mania were 3.5 times more likely to have eaten cured meat prior to their episode when compared with the group without a psychiatric disorder. It is often associated with bipolar disorder, a condition wherein people fluctuate between periods of mania and depression. And the authors stressed that eating cured meat on occasion probably won't trigger a manic episode in most people. The results were repeated when regular rat food was dosed with nitrates equivalent to that a human would consume in a hot dog or beef jerky stick.
"We tried to make sure the amount of nitrate used in the experiment was in the range of what people might reasonably be eating", says Yolken. Rats given a nitrate-free jerky did not show similar changes in behavior.
Reference Nitrated meat products are associated with mania in humans and altered behavior and brain gene expression in rats. To do so, they fed cured meats to rats and observed which ingredients led to hyperactivity.
Manic states can lead to unsafe risk-taking behaviour and can include delusional thinking, and most of those affected experience multiple hospitalisations in the course of their psychiatric illness. "Our results suggest that nitrated cured meat could be one environmental player in mediating mania".
"There's growing evidence that germs in the intestines can influence the brain", Yolken said.