Junk food
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After a recent experiment, scientists concluded that stress is harmful to health as much as junk food is to the digestive system. According to a paper published in Nature Scientific Reports, when female mice were exposed to stress, their gut microbiota, which is the micro-organism responsible for digestion and metabolic health, looked like that of an animal on a high-fat diet.

"Stress can be harmful in a lot of ways, but this research is novel in that it ties stress to female-specific changes in the gut microbiota," said BYU professor of microbiology and molecular biology Laura Bridgewater.

"We sometimes think of stress as a purely psychological phenomenon, but it causes distinct physical changes," she added.

The group of researchers led by Bridgewater conducted the study at Shanghai Jiao Tong University in China. During the study, researchers took a large group of 8-week-old mice and exposed half them (both male and female) to a high-fat diet. After 16 weeks, all the mice were exposed to mild stress for at least 18 days.

Following the exposure, researchers extracted microbial DNA from the faecal pellets and compared them to the excretory product taken before the experiment to study how gut microbiota was actually affected. Researchers have also measured the rodents' anxiety, depending on how much and where they travelled in an open arena.

The researchers drew the conclusive results by looking at the remarkable differences exhibited between genders: male mice portrayed more anxiety on a high-fat diet as compared to female mice. They also showed less activity in response to stress.

However, it was only female mice that showed increased rate activity in response to stress. In female mice, stress caused gut microbiota composition to shift greatly as if they were on a high- fat diet.

Though the researchers have conducted this study on animal alone, they believe that humans would have responded similarly.

"In society, women tend to have higher rates of depression and anxiety, which are linked to stress," said Bridgewater, Associate Dean of the BYU College of Life Science.

"This study suggests that a possible source of the gender discrepancy may be the different ways gut microbiota responds to stress in male vs female," she added.