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Major finding identifies nitrogen as key driver for gut
health

Date:

November 23, 2016

Source:

University of Sydney

Summary:

Scientists are one step
closer to understanding the link between different diet strategies and gut
health, with new research presenting the first general principles for how diet
impacts the microbiota.

Scientists are one
step closer to understanding the link between different diet strategies and gut
health, with new research presenting the first general principles for how diet
impacts the microbiota.

Researchers from the
University of Sydney have 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. The study is published today in Cell
Metabolism and led by researchers at the University of Sydney’s
Charles Perkins Centre.

“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. This is because there are many
complex factors at play, including food composition, eating pattern and genetic
background,” said lead author Associate Professor Andrew Holmes, from the
Charles Perkins Centre and School of Life and Environmental Sciences.

“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. 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.”

The balance of gut
bacteria in the microbiome plays a key role in such functions as immune
regulation and digestive wellbeing, and has been linked to other health
outcomes like obesity. Past studies have identified several patterns for how
diet influences the microbiome, yet this has not led to a workable model that
explains microbial response across many different types of diets.

This new research is
the latest in a series stemming from a seminal study in which 25 different
diets composed of different amounts of protein, carbohydrates and fat were
systematically varied in 858 mice.

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,” said Associate Professor Holmes.

“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.”

The researchers’ 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.

Researchers hope the
new findings will lay the foundations for more accurate computer simulations to
test hundreds of different diet variants, helping to better predict which
dietary combinations lead to optimal gut health.

“There are many
ways to achieve a good diet, and the same diet won’t work in the same way in
each person,” said co-author Professor Stephen Simpson, Academic Director
of the Charles Perkins Centre.

“The next step
will be to more rapidly characterise which dietary combinations promote the
best outcomes for each of our gut microbiomes, and to this end we are
developing a computer simulation for how this might work in practice.”

Story Source:

Materials provided by University of Sydney. Note:
Content may be edited for style and length.

Journal Reference:

1.    Andrew J. Holmes, Yi Vee Chew, Feyza
Colakoglu, John B. Cliff, Eline Klaassens, Mark N. Read,
Samantha M. Solon-Biet, Aisling C. McMahon, Victoria C. Cogger,
Kari Ruohonen, David Raubenheimer, David G. Le Couteur,
Stephen J. Simpson. Diet-Microbiome Interactions in Health Are
Controlled by Intestinal Nitrogen Source Constraints. Cell
Metabolism, 2016; DOI: 10.1016/j.cmet.2016.10.021

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