Gut feelings: Emotions, diets and microbiome link investigated in studies

08 May 2023 --- Research into the gut microbiome’s role in health continues to advance. US-based scientists at Harvard Medical School found a link between suppressing emotions and gut health among women but found no association with diets. Meanwhile, a China-based study found a link between Western diets and Crohn’s disease – a chronic inflammatory bowel disease in the gastrointestinal tract.

“Using dietary information obtained from the Food Frequency Questionnaire, we computed the Alternative Healthy Eating Index (AHEI) 2010 score – measuring adherence to a diet pattern based on foods and nutrients most predictive of chronic disease risk,” Dr. Shanlin Ke, a co-author of the study on emotions and the gut and a postdoctoral fellow at the Brigham and Women’s Hospital, Harvard Medical School, tells NutritionInsight.

“However, we found that the AHEI score was not significantly associated with the overall microbiome structures. Therefore, our results suggest that there were no significant differences in the gut microbiome of the women based on their dietary patterns in our cohort,” he continues.

Different life stages
We also spoke with Dr. Anne-Josée Guimond, a co-author of the study on emotions and the gut and a postdoctoral fellow at the Harvard School of Public Health, on how the gut microbiome might change depending on the life stage of women, pre- and post-menopause.

Guimond highlights that only one woman in the sample of 206 was premenopausal.The mean age of the women in the study was 61. Guimond highlights that only one woman in the sample of 206 was premenopausal.

“Taking pre- and post-menopause into account, in our study, all participants except one were menopaused at study baseline; because of this homogeneity, we did not include menopausal status as a covariate in our analyses,” she details.

“We did consider hormone therapy use, but we didn’t observe meaningful associations with the gut microbiome structure and composition,” she notes.

Guimond concludes that future studies must replicate the findings in younger women and assess whether menopausal status is linked with the gut microbiome structure and composition.

However, the China-based study focused on maternal Western diets did find a link between the gut microbiome and diets. In their study on mice, the researchers found that when mothers followed a Western diet – high in fat and sugar – there was an increased susceptibility to developing Crohn’s disease-like colitis.

The study stresses the importance of understanding how maternal diets impact children’s health throughout life.

Western diets
The China-based researchers found a link between maternal Western diets and increased risk for the child to develop Crohn’s disease.

The study says that ingesting western diets long term “can negatively affect gut homeostasis by disturbing intestinal microbiota, causing Paneth cell dysfunction and mucus barrier disruption, which can lead to increased susceptibility to infection and irritable bowel disease.”

It further notes that patients suffering from Crohn’s disease are rarely overweight or obese, despite its link to consuming high-fat and high-sugar diets. 

Additionally, it highlights other maternal factors that play a role in the fetus’s health and infant development, such as dietary intake or obesity, gut microbiota, breastfeeding and environmental exposures. The China-based study says that ingesting western diets long term can lead to increased susceptibility to infection and irritable bowel disease.

Following a Western-style diet showed to increase the levels of Bacteroidetes, “which express selective bile salt hydrolase activity and contribute to the generation of unconjugated bile acid and secondary bile acid DCA in offspring,” the study reads.

Emotions play a role?
Diving further into the role different emotions play in the gut, the study notes that prior research has found an association between positive and negative emotions with Lachnospiraceae.

“Among the emotion-related factors in our study, only suppression was significantly associated with alpha diversity. Notably, higher suppression levels were associated with lower values on the Simpson diversity index [a measure of diversity in the number of species] and less evenness in the gut microbial community at the species level. The reason only suppression was associated with diversity indexes is unclear,” the study reads.

When asked about whether emotions impact the gut microbiome or vice versa, Dr. Yang-Yu Liu, an associate professor of medicine at Harvard Medical School and co-author of the study, tells NutritionInsight:

“Unfortunately, our cross-sectional study cannot tell if emotions impact the gut or vice versa.” 

“While we used the most rigorous methods available to assess the association between the gut microbiome and emotions by accounting for a wide range of host factors, future interventional studies are warranted to ascertain the directionality of this relationship,” he concludes. 

By Beatrice Wihlander