EATING more turkey, chicken, nuts, eggs, seeds, beans, yoghurt, cheese and even chocolate could help those with inflamed guts, according to a new study.
A diet rich in tryptophan – one of the building blocks of protein – was found to increase the number of immune cells in the guts of mice, which kept harmful microbes that trigger inflammation in check.
Researchers from Washington University School of Medicine found that mice with a normal gut microbiome naturally grew a species of bacteria called Lactobacillus reuteri, which they discovered led to the growth of immune cells. Then, when fed more protein, the mice grew even more immune cells.
Mice without a healthy microbiome (the community of bacteria and fungi in our gastrointestinal tracts) were not able to grow the immune cells.
While human microbiomes also typically contain Lactobacillus reuteri, it is not yet known whether it serves the same function, although faults in tryptophan-metabolising genes have previously been linked to irritable bowel syndrome.
"The development of these cells is probably something we want to encourage since these cells control inflammation on the inner surface of the intestines," postdoctoral researcher Luisa Cervantes-Barragan said of the research published in the journal Science. "Potentially, high levels of tryptophan in the presence of L. reuteri may induce expansion of this population."
Inflammatory bowel disease (IBD – the term used to describe Crohn's disease and ulcerative colitis) affects about one in 250 people aged five to 40 and, according to the Gut Foundation, is on the rise in Australia.
"There is little evidence to suggest that dietary factors cause IBD," according to Crohn's and Colitis Australia. "Likewise, it is not possible to make your condition 'go away' permanently by adding or eliminating certain foods from your diet, or by eating only particular types of food."
Despite this, many with IBD have turned to a low-fodmap diet and find relief of symptoms through particular ways of eating.
Dr Joanna McMillan says while the protein study is "interesting", we need to be careful about extrapolating the findings to humans.
"We have incredibly complex microbiomes with many hundreds of different bacterial strains. We are all very different too and what one strain does in one person, another stain could be doing in another person, so I doubt just one species will prove to be a saviour for any condition," McMillan says. "It's the overall functioning of the microbiome and balance of the bugs that is crucial."
She adds that our diet contributes to the functioning and balance of our microbiome.
Too much of any one food type (like protein) can upset the balance, especially, McMillan says, if fermentable carbohydrate (fibres) intake is low.
"Research from Sydney University is showing that the balance between protein and fermentable carbs (they call them MACs – microbial accessible carbohydrates) is important," she explains.
McMillan adds that the new study "certainly warrants more research", and says there is still a question of how much protein and how often?
"The other factor is how much tryptophan makes it to the colonic microbiome? If the protein is digested and absorbed in the small intestine, as is usual, there won't be any left for use by the colonic bacteria," she says. "Would tryptophan potentially have to be delivered via a special supplement that doesn't release it until the colon? Just eating more protein won't cut it I suspect."
FODMAPS for IBD
FODMAPs stands for a group of carbohydrates Fermentable Oligo-saccharides, Disaccharides, Mono-saccharides and Polyols that can be poorly absorbed in the small intestine. The low FODMAP diet was developed by Monash University researchers for those with irritable bowel syndrome, yet many people with IBD have also adopted the diet and although it does not reduce inflammation, it can reduce symptoms.
"FODMAPs is a totally different issue as this is a therapeutic diet used to treat irritable bowel syndrome – not normally inflammatory bowel disease," McMillan explains. "The two are very different. There can be gut inflammation with IBS but right at the gut wall level and not always able to be picked up with traditional methods. IBD on the other hand has a much greater level of inflammation that can usually be seen during a colonoscopy."
