Cured Meats Strongly, Independently Tied to Increased Mania Risk

Megan Brooks

July 19, 2018

Eating nitrate-cured meats such as beef jerky and other processed meat snacks has been strongly linked to an increased risk for mania, new research shows.

A study of roughly 1100 adults showed that those who were hospitalized for a manic episode were more than three times more likely to have ever eaten nitrate-cured meats than those who did not have a history of a serious psychiatric disorder.

"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," lead investigator Robert Yolken, MD, of Johns Hopkins University School of Medicine in Baltimore, Maryland, said in a statement.

The study was published online July 18 in Molecular Psychiatry.

Diet Critical to Mental Health

It has been increasingly recognized that diet is a source of environmental factors that may contribute to bipolar disorder and other neuropsychiatric disorders.

To investigate further, the researchers collected demographic, health, and dietary data on 758 adults aged 18 to 65 years who had been diagnosed with mania or other psychiatric disorders and a control group of 343 adults who had not been diagnosed with a psychiatric disorder.

Food exposures were assessed using a questionnaire, developed by the research team, that asked participants whether or not they had eaten certain types of food.

After adjusting for potential confounding factors, a history of eating nitrate-cured meats such as beef jerky and meat sticks, but not other meat or fish products, was "strongly and independently" associated with current mania (adjusted odds ratio, 3.49; 95% confidence interval, 2.24 - 5.45), the investigators report.

I don't think it's totally specific for mania. Dr Robert Yolken

Nitrate-cured meats in the diet were not significantly associated with a diagnosis of any other neuropsychiatric disorder, including schizophrenia, schizoaffective disorder, bipolar disorder, bipolar depression, or major depressive disorder.

"It looked like there might be some increases in some of the other disorders, so I don't think it's totally specific for mania, but at the sample size we had, it wasn't significant. We just need larger numbers to look at bipolar depression and major depression," Yolken noted in an interview with Medscape Medical News.

No other foods were found to be significantly associated with mania or any of the other disorders.

The questionnaire did not ask about the frequency or timing of cured meat consumption, so the investigators were not able to draw conclusions about how much cured meat in the diet may boost mania risk. It's a question they plan to assess in a future study.

Further Evidence

Consistent with their results in humans, a series of experiments the investigators performed in healthy rats showed manialike hyperactivity in the animals within a few weeks of their being maintained on diets to which nitrates had been added.

The animals also were found to have alterations in brain pathways that have been implicated in human bipolar disorder, as well as changes in intestinal microbiota.

In contrast, rats fed a diet high in meats prepared without nitrates did not show behavioral changes or hyperactivity.

The investigators point out that it's important to note that the amount of nitrates consumed by the rats was equal to the amount a human might ingest in a daily snack, such as one hotdog or one stick of beef jerky.

"We tried to make sure the amount of nitrate used in the experiment was in the range of what people might reasonably be eating," said Yolken.

The investigators note that to the best of their knowledge, this is the first study linking exposure to cured meat with a neuropsychiatric disorder.

"While further investigations are needed, individuals at risk for mania may consider limiting ingestion of added dietary nitrates," they write.

Impact of Diet Underestimated

Commenting on the findings for Medscape Medical News, Dolores Malaspina, MD, director of the psychosis program at Icahn School of Medicine at Mount Sinai in New York City, said that, although interesting, studies in humans and animals "stop short of proof of causation.

"Certainly, many people in a disorganized state who don't get regular meals may have more intake of turkey jerky because it's convenient or fast or easy. I do see patients who buy a bag of turkey jerky rather than healthful nutrition," said Malaspina.

"With such a finding [and] while evidence accumulates, it may be worthwhile for patients with severe mental illness to avoid these kinds of foods. Diet is crucial in mental health, and I think we have underestimated the impact of diet for brain health, and we need to keep pursuing studies of dietary intakes and supplements and mental health," Malaspina added.

The study was supported by the National Institute of Mental Health and the Stanley Medical Research Institute. The authors and Dr Malaspina have disclosed no relevant financial relationships.

Mol Psychiatry. Published online July 18, 2018. Abstract

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