Sydney, Nov 27 (IANS) Dietary combination of protein and carbohydrate may help promote good gut health as such a diet encourages cooperation between ourselves and bacteria in our gut, suggests new research. "There are many different diet strategies that claim to promote gut health, and until now it has been very difficult to establish clear causality between various types of diet and their effect on the host's microbiome," said led author Andrew Holmes, Associate Professor at the University of Sydney in Australia. "This is because there are many complex factors at play, including food composition, eating pattern and genetic background," Holmes said. In this study, the researchers found that the availability of intestinal nitrogen to microbes in the gut plays a key role in regulating interactions between gut microbes and their host animal. "This research really lays the groundwork for future modelling by setting out the rules for a general model of how diet shapes the gut ecosystem," Holmes said. "The simple explanation is that when we eat in a way that encourages cooperation between ourselves and bacteria we achieve a good microbiome, but when we eat in a way that doesn't require cooperation this lets bacteria do whatever they want -- and mischief can ensue," Holmes explained. Despite the huge diversity of gut bacteria, two main response patterns emerged in the study -- microbe species either increased or decreased in their abundance depending on the animal's protein and carbohydrate intake. "The largest nutrient requirements for our gut bacteria are carbon and nitrogen in the foods we eat. As carbohydrates contain no nitrogen but protein does, the bacterial community response to the host animal's diet is strongly affected by this diets' protein-carbohydrate ratio," Holmes said. "The fact that this same pattern was seen across almost all groups of gut bacteria indicates that the makeup of the microbial ecosystem is fundamentally shaped by a need to access nitrogen in the intestinal environment," Holmes added. This new research -- published in the journal Cell Metabolism -- is the latest in a series stemming from a study in which 25 different diets composed of different amounts of protein, carbohydrates and fat were systematically varied in 858 mice. The researchers said their new model suggests that while high-carbohydrate diets were the most likely to support positive interactions in the microbiome, such benefits were relative to the protein intake of the host animal.