New research in Cell uses turmeric spice to unlock secrets of gut bacteria

The ingredient turmeric, a spice that is commonly used in South Asian food, was used to explore the complex interaction between diet and gut microbes

The effect of diet on gut motility—the time that it takes for food to pass through the digestive system—is most obvious when a person is travelling through different countries and trying different food. But a new study in Cell has found that it can also be affected by the unique composition of the bacteria communities (the ‘gut microbiota') within the gut itself.

The researchers, including the director of icddr,b’s Centre for Nutrition and Food Security, Dr Tahmeed Ahmed, modeled a “traveller’s diet” in mice by feeding them a series of different international cuisines over time, to observe the speeding-up or slowing-down of gut motility as a result of dietary changes. The quickest transit times were seen in the mice that had highly contrasting diet and gut community combinations, such as mice who were colonized with bacteria from a US resident and fed a Bangladeshi diet.

The scientists also observed that even a single ingredient, like turmeric, can have very different effects on gut motility depending on the composition of the gut communities. Previous studies have shown that turmeric stimulates bile secretion and that this subsequently speeds up the time that it takes for food to pass through the digestive system. In this study, however, the scientists identified that this particular effect of turmeric is dependent on the preexistence of a specific enzyme in the gut, bile salt hydrolase (BSH), which metabolizes bile acids. Turmeric did not speed up gut motility in mice that did not have the BSH enzyme.

Photo by Carlos Lorenzo, CC BY-NC-ND 2.0

Gut motility is a key factor in nutritional status and gut health, as high motility – linked to disorders like irritable bowel syndrome – can result in nutrients from food not being absorbed properly. In an increasingly globalised world, where many cuisines can be consumed in even one day, understanding the effect of dietary “travel” is important to ultimately understanding disorders of the gut.

The turmeric experiment was one of several that looked at the effect of different culinary diets on the passage of food through the digestive system. Of all the dietary ingredients that were used, it was turmeric that was found to have a significant impact on gastrointestinal function. For the full details of the study, in which the scientists tested diets from the USA, rural Venezuela, rural Malawi and urban Bangladesh, refer to the full paper in Cell.

The researchers say that the findings of this study have important implications for the future prescription and use of probiotic treatments for disorders of the gut that affect motility, such as irritable bowel syndrome. The scientists suggest that, in future, both treatment and dietary recommendations should be based on the structural and functional features of an individual’s microbiota. They will use this knowledge of ‘good’ dietary ingredients and ‘good’ microbiota to develop novel diets for the treatments of nutritional disorders.