A study on the nutritional habits of more than 1,000 people with and without psychiatric disorders has found a link between the consumption of nitrated sausages such as beef jerky and meat sticks and episodes of mania, a severe neuropsychological disorder, defining characteristics of bipolar disorder (BPD ). Results of the study, led by Robert H. Yolken, MD, Theodore and Vada Stanley Professor of Pediatric Neurovirology at the Johns Hopkins University School of Medicine, showed that people who were hospitalized for an episode of mania in the hospital were more than three were more likely that they have ever eaten nitrate-dried meat than those without a severe psychiatric disorder. "We looked at different dietary conditions, and sausages were really outstanding," says Dr. Yolken. "It's not just that people with mania have an abnormal diet."
Further experiments showed that healthy rats fed nitrate-hardened meat or adding nitrates caused mania-like hyperactivity within a few weeks. The researchers suggest that their findings emphasize evidence linking nutritional factors to the risk of neuropsychiatric conditions such as BPD. In their published work in Molecular Psychiatry they report that the findings may also "lead to new methods for the prevention of mania and the development of novel therapeutic interventions."
"Future work on this association could lead to dietary results interventions to reduce the risk of manic episodes in people who have bipolar disorder or who are otherwise prone to mania," Dr. Yolken. The team's published work is titled: "Nitrate meat products are associated with human mania and altered behavior brain gene expression in rats."
Previous studies have identified a number of genetic risk factors for BPD and other neuropsychiatric disorders, but these are not the complete answer, the authors point out. The resulting "heritability gap" points to "the role of the environment in mediating and disseminating neuropsychiatric disorders." Diet has been highlighted as a potentially important environmental factor that could contribute to the risk of BPD and other neuropsychiatric disorders through a variety of mechanisms from neurotoxicity by traces of heavy metals to changes in gut microbiota and the gut-brain axis.
To clarify the possible link between environmental pollution and psychiatric conditions, Dr. Ing. Yolken's team undertook a study collecting demographic, health and dietary data for 1
The main inclusion criterion for participants with mania was the current hospitalization for symptoms of mania or hypomania. Patients with mania have been diagnosed with various forms of bipolar disorder or schizoaffective disorder. The food exposure data was collected using a questionnaire developed by the researchers, asking participants whether or not they had eaten certain types of food, but did not go into details such as the amount or period
"unexpected analyzes "found that a history of eating nitrate-hardened meats such as jerky and meat sticks – but not dry-smoked meats such as salami or prosciutto – regardless of being hospitalized with acute mania, even after adjusting for confounding factors. No other diet has been associated with mania, and nitrate-hardened meat has not been directly linked to a diagnosis of any other neuropsychiatric disorder, including schizophrenia or schizoaffective disorder, BPD, bipolar depression, or major depressive disorder.
Human study was not conducted. To investigate the causes and effects, the team next examined the possible effects of nitrate-hardened meat on the behavior of healthy rats. In collaboration with Johns Hopkins colleagues Seva Khambadkone and Kellie Tamashiro, Ph.D., Associate Professor of Psychiatry and Behavioral Science, the researchers performed three series of experiments in which animals were fed either normal rat diets or nitrate-supplemented diets, meat preparations, sausages without addition of nitrates or non-nitrate-hardened meat to which nitrate has been added separately. Importantly, the amount of nitrate consumed by the rats was equivalent to the amount that a human could take in a daily snack, such as a hot dog or dry beef. "We tried to make sure that the amount of nitrate used in the experiment was in the range of what people could reasonably eat," commented Drs. Yolken.
Within a few weeks, the rats consumed nitrate-hardened meat or nitrates developed locomotor hyperactivity that mimicked symptoms of human mania.This animals also showed changes in hippocampus pathways in the brain, which implies in human bipolar disorder, as well as changes in their gut microbiota In contrast, a high-meat diet prepared without nitrates did not induce behavioral changes or hyperactivity
The exposure of food to nitrate-hardened meat has been previously associated with disorders including various cancers, asthma and chronic obstructive pulmonary disease, but the underlying ones Mechanisms are not understood, the researchers say, "to our knowledge, this is the first study linking exposure to cured meat to a neuropsychiatric disorder," the scientist points out indicates that further studies will be needed. However, they write: "Persons at risk for mania may consider limiting the intake of additional nitrates in the diet."
"It is clear that mania is a complex neuropsychiatric condition and that both genetic susceptibility and environmental factors are likely to be involved in the development and onset of disease severity of bipolar disorder and associated manic episodes," commented Khambadkone. "Our results suggest that nitrated salted meat could be an environmental factor in mediating mania."
Dr. Yolken's group has previously reported results showing that bipolar disorder patients treated with probiotics are less likely to be hospitalized after a manic episode within the next six months. "There is more and more evidence that germs in the gut can affect the brain," Dr. Yolken. "And this work on nitrates opens the door for future studies on how this could happen."