A new study out of Johns Hopkins Medicine has determined there may be a link between mania and eating processed meats cured with nitrates. But before you throw out the rasher of bacon in your fridge or opt out of having beef jerky on your next camping trip, there's a few things you should know about the potential link between processed meats and manic episodes, and the first of those things is that you shouldn't panic.
First thing's first: what is a manic episode? A manic episode is defined as a "mood state characterized by period of at least one week where an elevated, expansive, or unusually irritable mood exists," PsychCentral writes. Symptoms of mania can include hyperactivity, irritability, insomnia or difficulty sleeping, or excess energy. Experiencing mania is a primary symptom of bipolar disorder, but it can also be present in people with schizoaffective disorder, too.
The study, which was published July 18 in the journal Molecular Psychiatry, was originally designed to examine the ways that "certain diets and potentially types and amounts of bacteria in the gut may contribute to mania and other disorders that affect the brain," according to a press release about the study. It was also specifically "not designed to determine cause and effect." In fact, the study's lead author, Dr. Robert Yolken, didn't focus in on mania or on processed meats until after data from the earliest parts of the study started coming together.
To see whether there could be a link, Yolken spent 10 years collecting information on 1,101 people between the ages of 18 and 65. Some participants had psychiatric disorders, and some did not. Per the study statement, 55 percent of participants were female, 55 percent were white, and 36 percent were black. The data Yolken and colleagues collected from these 1,101 participants showed that "unexpectedly, among people who had been hospitalized for mania, a history of eating cured meat before hospitalization were approximately 3.5 times higher than the group of people without a psychiatric disorder," according to the study statement. "We looked at a number of different dietary exposures and cured meat really stood out," Yolken said in the statement. "It wasn't just that people with mania have an abnormal diet."
While researchers could potentially link consumption of cured meats with mania, they were unable to link nitrates to schizoaffective disorder, bipolar disorder ("in people not hospitalized for mania"), or major depressive disorder. The study statement indicates that no other foods, processed or unprocessed, "had significant association with any of the disorders, or with mania." The researchers couldn't determine how much cured meat consumption may be linked with mania, though, because the survey they took from participants didn't ask about how often they ate it or the time frame relevant to their hospitalization for mania.
To further explore results from the 1,101 human participants, Yolken then teamed up with Dr. Kellie Tamashiro and researcher Seva Khambadkone to examine the affects of nitrate-prepared meats on rats. They took two groups of rats, feeding one regular rat food, and feeding the other both normal food and "a piece of store-bought, nitrate-prepared beef jerky every other day," according to the study statement. Yolken, Tamashiro, and Khambadkone found that within two weeks, the group of rats eating jerky "showed irregular sleeping patterns and hyperactivity," two behaviors commonly associated with mania.
And to even further test their hypothesis that it was nitrates behind the potential link, the researchers then had a production company custom-make a beef jerky without nitrates. When they repeated the experiment with the two rat groups, this time feeding one group nitrate-prepared jerky and the other nitrate-free jerky, the rats who ate jerky with nitrates "again showed sleep disturbances and hyperactivity similar to that seen in patients with mania."
Despite these results, the researchers said in the study statement that "occasional cured meat consumption is unlikely to spur a manic episode in most of the population." Khambadkone also said that the development of psychiatric disorders that involve manic episodes is likely tied to "both genetic vulnerabilities and environmental factors."
Moving forward, Yolken plans to take these findings and continue investigating the effects of gut bacteria on our mental health. "There's growing evidence that germs in the intestines can influence the brain," he said in the study statement. "And this work on nitrates opens the door for future studies on how that may be happening."
So though the idea that consumption of nitrates may be linked to manic episodes may be a little frightening, do not worry: You can rest assured that researchers seem to indicate it's still safe for most people to enjoy processed meat in moderation.