Understanding how diet affects gut microbes and thereby influences human health might lead to targeted dietary strategies. A clinical trial now provides some steps on the path towards this goal.
Dietary fibre is the indigestible part of plant foods. Is mostly in vegetables, fruits, whole grains, and legumes. There are two types of fibre, soluble and insoluble, both play important roles in health.
- Insoluble fiber does not dissolve in water and adds bulk to the stool, preventing constipation.
- Soluble fiber absorbs water, forming a gel-like substance in the digestive system. It may help lower cholesterol levels and help regulate blood sugar levels.
There is growing evidence that our normal resident gut microorganisms can affect our health. Promoting beneficial commensal microbes through a type of nutritional supplement, called prebiotic is an area of intensive scientific and medical research. Delannoy- Bruno et al. studied dietary fibre, a family of substances of pronounced physiological virtues that are predominantly metabolized by commensal microbes.
Delannoy-Bruno and colleagues used germ-free mice, animals raised and maintained in a sterile environment that are therefore devoid of the usual resident microbes of any sort. They then colonized the gut of each of nine mouse groups with the microbiome of one of nine women classes as obese. They were fed with low fibre, high fat diet, coupled with period fibre supplementation. Their microbiome was characterized to assess gene content before, during and after each episode of supplementation. After each cycle a period of washout to enable intestinal clearing of fibres was followed.
Their results showed that exposure of the microbial population to a particular fibre resulted in a greater presence of genes that encode proteins needed for the metabolism of that fibre. For example, consumption of cellulose-containing pea and orange fibre led to a higher representation of genes encoding the β-glucosidase enzymes that hydrolyse such fibre, probably owing to the proliferation of bacteria that can use cellulose as an energy source.
In mice inoculated with human microbiomes, similar signatures of fibre responsive genes became highly abundant through the expansion of various bacterial taxa including Bacteroides.
These results highlight that a shift in microbial gene abundance, rather than a shift to a particular community structure in terms of species present, is a common denominator in the response pattern to dietary interventions across individuals.
They also tested whether these findings have relevance to human biology and if consumption of multiple fibre types results in a greater microbiome shift than was observed upon consumption of pea fibre alone as a supplement. The microbial gene responses to fibre supplementation in humans largelly resembled those observed in mice. Also, results indicate that the more types of fibre an individual consumes, the greater the rise in the number of microbial genes present that are involved in fibre metabolism.
The results propose that human dietary responses are specific to food components, and that these components might be tailored to the individual to optimize their dietary response. These responses are driven by different variables, like physiological traits, features of the food components and gut microbiome composition and function, which has been suggested as a key modulator of physiological food responses and associated differences in such responses between individuals.
The current recommendation of fiber is 14 grams per 1,000 calories consumed. The study researchers provide a framework that paves the way for optimizing an individual’s fibre consumption, based on fibre type and their microbiome fibre-degradation signatures.
The study provides valuable mechanistic insights into the microbial contributions to human dietary responses and also brings us closer to the integration of precise microbiome engineering with evidence-based dietary sciences.
Source link: https://www.nature.com/articles/d41586-021-01601-y