Hot Dogs and Beef Jerky Linked to Mania in Study

A chemical used to cure meat has been linked to a symptom of mental illness, according to a study.

Nitrates, which are used to cure products such as hot dogs, beef jerky, salami and other processed meats could contribute to mania, researchers at Johns Hopkins Medicine found.

Mania is defined as a state of heightened mood, energy and arousal that can last from a few weeks to several months. It is most common in those who have bipolar disorder, but it can also affect individuals with schizoaffective disorder: a condition that includes the symptoms of schizophrenia and depression or bipolar disorder.

Someone experiencing mania is more likely to engage in dangerous, risky behavior and is more susceptible to delusional thoughts.

To arrive at this conclusion, the team collected data on 1,101 individuals with and without diagnosed psychiatric disorders between 2007 and 2017.

The data included health, dietary and demographic information about the participants, who were between 18 to 65 years old. Around 55 percent of the participants were female, 55 percent were Caucasian, and 36 percent were African-American.

Initially, the researchers set out to investigate whether being exposed to infections, including those passed on in food, were linked to mental illness.

But by delving into a decade's worth of data, the researchers were surprised to find that those who had been hospitalized with mania were 3.5 times more likely to have consumed cured meat prior to their episode when compared with the group without a psychiatric disorder.

The researchers did not find a link between cured meats and conditions such as bipolar disorder, major depressive disorder or schizoaffective disorder in people not hospitalized for mania. And other foods, like fish or untreated meats, were not linked to mania.

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To bolster their results, the scientists fed rats nitrates. They found the animals showed signs of hyperactivity and irregular sleeping patterns compared with those that ate regular rat food. And when the experiment was repeated using nitrate-free beef jerky, the animals behaved similarly to the control group, while the rats who ate meat cured with nitrates had sleep problems and hyperactivity. 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.

The animals that were fed nitrates also had a different makeup of bacteria in their digestive systems, and showed differences in molecular pathways in the brain linked to bipolar disorder.

Dr. Robert Yolken, lead author of the study and professor of neurovirology in pediatrics at the Johns Hopkins University School of Medicine, said in a statement: "We looked at a number of different dietary exposures and cured meat really stood out. It wasn't just that people with mania have an abnormal diet."

The research followed a study published by Yolken's team that suggested probiotics, which aid the bacteria in our digestive system, could reduce the likelihood of an individual being rehospitalized in the following six months.

"There's growing evidence that germs in the intestines can influence the brain," said Yolken. "And this work on nitrates opens the door for future studies on how that may be happening."

The authors of the study, published in the journal Molecular Psychiatry, hope the findings will help in preventing mania and developing treatments for mental disorders.

However, they emphasized that eating cured meat occasionally was unlikely to trigger mental illness in the average person.

The team acknowledged that its results didn't prove processed meats caused mania or mental illness, and that further research was needed into the association.

Seva Khambadkone, an M.D. and Ph.D. student at Johns Hopkins who took part in the study, said: "It's clear that mania is a complex neuropsychiatric state, and that both genetic vulnerabilities and environmental factors are likely involved in the emergence and severity of bipolar disorder and associated manic episodes.

"Our results suggest that nitrated cured meat could be one environmental player in mediating mania."

The study is the latest piece of research to raise concerns about how processed meats affect our physical and mental health, as nitrates have previously been linked to cancers and neurodegenerative diseases.

In 2015, the World Health Organization warned that eating processed meats such as hot dogs, sausages or bacon could lead to bowel cancer in humans, and that red meat was a likely contributor to the disease.