Mania Linked to Beef Jerky: Hot Dogs and Bacon May Be Next

RESEARCH UPDATE

Dr Aiken is Instructor in Clinical Psychiatry at the Wake Forest University School of Medicine and the Director of the Mood Treatment Center in Winston-Salem, NC. He is Editor in Chief of The Carlat Psychiatry Report.

New Study Finds That Nitrate-Cured Meats May Play a Causative Role in Mania

Nitrate-cured meats may increase the risk of mania, according to a study published in Molecular Psychiatry.¹ That includes meat sticks, beef jerky, and turkey jerky, but not prosciutto, which is dry-cured without nitrates.

The finding was striking, with a large odds ratio of 3.5. It surprised the research team, who set out to investigate the relationship between diet and psychiatric illness at the Sheppard Pratt Health System. Their cohort of 1101 subjects included patients with bipolar mania, bipolar depression, unipolar depression, schizophrenia, schizoaffective disorder, and normal controls. Midway through the 10-year study, they noticed a sharp spike of dry cured meats among the patients hospitalized for mania. Other psychiatric illnesses did not show this association, and the finding held up after controlling for age, gender, race, current cigarette smoking, body mass index, socioeconomic status, and multiple statistical comparisons.

To further test that association with a controlled design, they added a series of animal studies in collaboration with the Nutrition Department at Purdue University. Compared with a standard diet, beef jerky increased manic behavior in rats, as measured by increased locomotor and novelty-seeking behavior. Additional experiments suggested that nitrates were part of the problem. Adding nitrates to the standard diet also increased manic behavior, although to a lesser degree than the beef jerky. When fed dried beef that was free of nitrates, the rats showed no increase in mania.

Mechanisms

How can dietary nitrates trigger mania? Nitric oxide is one possibility. This gas rises with nitrate consumption and is increased in patients with bipolar disorder. Post-mortem analysis of the rat brains found alterations in brain regions that interact with nitric oxide: serotonin receptor signaling, nuclear factor (NF)-κB signaling, bacterial pattern recognition, and sphingosine-1-phosphate signaling. With the exception of sphingosine, each of those pathways has been linked to mania in human studies.

Another hypothesis is that the nitrate-rich foods alter the gut flora in ways that elevate the risk of mania. That may sound far-fetched, but it’s supported by basic science—the mind-gut connection—as well as by a recent controlled study (from the same Sheppard Pratt group) that found significant preventative benefits with probiotics after a manic episode.² Indeed, the nitrate-fed rats had higher counts of two bacterial species associated with behavioral and cognitive changes in animals: Lachnospiraceae and Erysipelotrichales.