However, some of the ways the human body works are still a mystery. Now, gastroenterology scientist Jan Huizinga and a group of McMaster researchers have cleared up one aspect of how the bowels move that had mystified scientists until now. There is a pacemaker in the gut that helps move things along, just like in the heart. But when food goes into the intestine, it needs to move along, but it also needs mixing, and the food must stay in the intestine for a few hours so nutrients can be absorbed. Huizinga and his team found out that certain nutrients induce a second pacemaker that interacts with the first one to create stationary back-and-forth movements that optimize nutrient absorption. This second pacemaker is also induced by butyric acid, which is generated by the bacteria in our gut. “In the long run, it’s simple,” said Huizinga. “Its like when a stone is dropped in water, it creates waves or motion that pushes things along, but when a second stone is dropped in the water, the movement changes to up and down, appearing to stay in the same place.” The discovery was made by Huizinga, a professor of medicine, and his researchers at the Farncombe Family Digestive Health Institute at McMaster, working with investigators of Wuhan University in China and colleagues at the University of Toronto. The paper was published by the science journal Nature Communications on Feb. 24. The discovery is important, as it gives direction for development of drugs or nutrients which will combat disorders when people have diarrhea, constipation, bloating or malabsorption of nutrients from food. With diarrhea, the segmentation activity is too low; in constipation, the same activity is too high and pain related to eating is often caused by abnormal contractions, explained Huizinga. The research was funded by the Canadian Institutes of Health Research and the National Natural Science Foundation of China. Several members of the research team are supported with scholarships from the Canadian Association of Gastroenterology, Hamilton Health Sciences and the Ontario government.