The research team said that their new study adds to evidence that certain diets and potentially the amounts and types of bacteria in the gut may contribute to mania and other disorders that affect the brain.

One to three percent of the population of the United States is estimated to have bipolar disorder.

Study Design and Results

Yolken and colleagues collected demographic, health and dietary data on 1,101 individuals aged 18 through 65 with and without psychiatric disorders between 2007 and 2017. About half of the participants were female, of which the same number of participants were Caucasian and 36 percent identified themselves as African-American.

The psychiatric disorder patients were already receiving care at the Sheppard Pratt Health System in Baltimore and were recruited from there. Individuals without any history of psychiatric disorders were recruited from announcements that were posted at local health care facilities and universities in the vicinity.

The records between 2007 and 2017 were analyzed which revealed that

• The people hospitalized with mania had a history of eating cured meat before admission which was approximately 3.5 times higher than the group of people admitted without a psychiatric disorder.
• In people not hospitalized for mania or in major depressive disorder, there was no association between cured meats and a diagnosis of schizoaffective disorder, or bipolar disorder.
• No significant association was found with other foods and mania and similar disorders.

Nitrates which have been previously linked to some cancers and neurodegenerative diseases could be the suspect in this case too and could explain the occurrence of mood states such as mania.

Yolken collaborated with Kellie Tamashiro, Ph.D., associate professor of psychiatry and behavioral sciences, and M.D./Ph.D and his students from Johns Hopkins to get to the bottom of the nitrate-mania association.

Study - Impact of Nitrates on Rats

• Kellie Tamashiro and his students did a small experiment on otherwise healthy rats which were fed every other day. They found that within two weeks, the group of rats that received both normal chow and a piece of store-bought, nitrate-prepared beef jerky showed irregular sleeping patterns and hyperactivity compared to the group of rats that received only normal rat chow.
• The team wanted to repeat the experiment and this time asked a Baltimore-based beef jerky company to create a special nitrate-free dried beef. The result was that the rats that ate the nitrate-free meat behaved similarly to a control group whereas the rats that consumed the store-bought, nitrate-prepared jerky once again showed sleep disturbances and hyperactivity similar to that seen in patients with mania.
• Similar results were obtained when they repeated the experiment with a specially formulated rat chow that either contained added nitrate or no nitrate. The rats which ate the nitrate-added chow behaved like the rats that had the nitrate-prepared jerky.
• The amount of nitrate that the rats ate on a daily basis when scaled to the size of what a human ate was equivalent to a beef jerky stick or hot dog.
• Scientists also analyzed the differences in the gut bacteria of the different rat groups; rats which ate the nitrate meals had different patterns of bacteria living in their intestines than the rats that did not get the nitrate-processed foods.
• The two groups of rats also showed differences in several molecular pathways in the brain that have been previously implicated in bipolar disorder.

Mania is a complex neuropsychiatric state and more than one factor is known to cause it. There are genetic vulnerabilities and environmental factors that are likely involved in the emergence and severity of bipolar disorder and associated manic episodes.

This study says that nitrate-cured meat could be one environmental player in mediating mania among the multiple factors involved. The authors say it is still too early to take any clinical messages from the results.

A recent study by Yolken's group showed that when people with bipolar disorder are given probiotics (known to change the composition of gut bacteria) after a manic episode, they are less likely to be rehospitalized in the following six months.

"There's growing evidence that germs in the intestines can influence the brain," says Yolken. "And this work on nitrates opens the door for future studies on how that may be happening." Further studies will focus on how much cured meat boosts one's risk of mania.

Source: Medindia