Cured meats such as salami or jerky may worsen the symptoms of some people with mental illness, researchers reported Wednesday.
Chemicals used to cure meats like salami and hot dogs may be linked to a mood disorder called mania, researchers report.
Other research has found rats exhibited mania-like behavior after a few weeks of eating nitrate-laden foods, and that their gut bacteria was altered.
"I think that for people with mania, and perhaps other disorders as well, there might be environmental triggers that you can control", he said. Researchers, hence, are looking at diet as a plausible causative factor among other things.
Eating processed meat could raise someone's risk of having a manic episode.
"There's growing evidence that germs in the intestines can influence the brain", said study lead author Dr. Robert Yolken.
The researchers are quick to say that they have not proven that eating cured meats causes mental illness, or even that a little jerky hurts someone with, say, bipolar disease.
What is mania? Simply put, it's a serious neuropsychiatric condition commonly identified as the "wild" part of a bipolar mood swing marked by euphoria, insomnia, hyperactivity, risk-taking behavior and detachment from reality (as opposed to the lethargy of the depression side).
Meat sticks and jerky are popular snacks in the USA, and less so in the United Kingdom, however nitrates are used here as preservatives for a minority of sausages and may also be in bacon and burgers. But researchers at Johns Hopkins Medicine wanted to investigate the impact of other environmental factors such as certain diets, particularly those higher in cured and processed meats.
"We looked at a number of different dietary exposures and cured meat really stood out."
Among people hospitalized for psychiatric disorders, people who ate cured meat, which included salami and various forms of dried meat sticks and jerky, had a almost 3.5 higher likelihood of having been admitted for mania, compared to people in the control group, who did not have psychiatric conditions.
"The cured meat products were generally in the form of meat sticks, beef jerky and turkey jerky, which are cured meat products generally prepared with added nitrates".
Genetic and other risk factors have been linked to manic episodes that characterise bipolar disorder.
Next, the team worked with a Baltimore beef jerky company to create a special nitrate-free dried beef.
So the researchers tried testing rats, feeding them beef jerky loaded with nitrates every other day. While the team also cautions that it's too early to take any clinical messages from the results, and occasional cured meat consumption is unlikely to spur a manic episode in most of the population, Yolken said the findings add to evidence of the multiple factors that contribute to mania and bipolar disorder.
In previous research, Yolken and his colleagues discovered that when given probiotics that alter the bacteria of the gut, patients with bipolar disorder were less likely to be hospitalized six months later.