Equipping People To Make Sense Of What They Are Told
Insoluble dietary fibre, or roughage, not only keeps you regular, say Australian
scientists, it also plays a vital role in the immune system, keeping certain diseases
at bay.
The indigestible part of all plant-based foods pushes its way through most of the
digestive tract unchanged, acting as a kind of internal broom. When it arrives in
the colon, bacteria convert it to energy and compounds known as 'short chain fatty
acids'. These are already known to alleviate the symptoms of colitis, an inflammatory
gut condition.
Similarly, probiotics and prebiotics, food supplements that affect the balance of
gut bacteria, reduce the symptoms of asthma and rheumatoid arthritis, also inflammatory
diseases. Until now no-one has understood why.
Published October 28 in Nature, breakthrough research by a Sydney-based team makes
new sense of such known facts by describing a mechanism that links diet, gut bacteria
and the immune system.
PhD student Kendle Maslowski and Professor Charles Mackay from the Garvan Institute
of Medical Research, in collaboration with the Co-operative Research Centre for Asthma
and Airways, have demonstrated that GPR43, a molecule expressed by immune cells and
previously shown to bind short chain fatty acids, functions as an anti-inflammatory
receptor.
"The notion that diet might have profound effects on immune responses or inflammatory
diseases has never been taken that seriously" said Professor Mackay. "We believe
that changes in diet, associated with western lifestyles, contribute to the increasing
incidences of asthma, Type 1 diabetes and other autoimmune diseases. Now we have
a new molecular mechanism that might explain how diet is affecting our immune systems."
"We're also now beginning to understand that from the moment you're born, it's incredibly
important to be colonised by the right kinds of gut bacteria," added Kendle. "The
kinds of foods you eat directly determine the levels of certain bacteria in your
gut."
"Changing diets are changing the kinds of gut bacteria we have, as well as their
by-products, particularly short chain fatty acids. If we have low amounts of dietary
fibre, then we're going to have low levels of short chain fatty acids, which we have
demonstrated are very important in the immune systems of mice."
Mice that lack the GPR43 gene have increased inflammation, and poor ability to resolve
inflammation, because their immune cells can't bind to short chain fatty acids. There
is plenty of evidence to suggest that bacteria and their by-products play an important
role.
An American study published in Nature in 2006 2 compared the bacteria in the guts
of obese and lean people.
The obese people were put on a diet, and as they lost weight their bacteria profile
gradually came to match that of the lean people.
Another study looked at what diets might do to short chain fatty acid levels. Obese
those were put on three different diets over time -- high, medium and low fibre --
and there was a direct correlation between the level of carbohydrate, or fibre, in
the diet and the level of short chain fatty acids.
The conclusions drawn from the current research provide some of the most compelling
reasons yet for eating considerably more unprocessed whole foods -- fruits, vegetables,
grains, nuts and seeds.
Dietary fibre, of course, has many known health benefits in addition to those discussed
above, including reduced risk of cardiovascular disease and certain cancers , and
various health organizations around the world recommend daily minimum levels.
It is certain that the majority of people in countries like Australia, the United
States and Britain eat much less fibre than they need to stay healthy.
"The role of nutrition and gut intestinal bacteria in immune responses is an exciting
new topic in immunology, and recent findings including our own open up new possibilities
to explore causes as well as new treatments for inflammatory diseases such as asthma,"
said Professor Mackay.
Source -Garvan Institute of Medical Research (2009, October 28). Diet And Intestinal
Bacteria Linked To Healthier Immune Systems. - ScienceDaily
Journal Reference - Maslowski et al. Regulation of inflammatory responses by gut
microbiota and chemoattractant receptor GPR43. Nature, 2009; 461 (7268): 1282 Internet
Page
In several trials, those with colitis have been given dietary fibre, resulting in
beneficial anti-inflammatory effects:
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Australian Dietary Guidelines, produced by the National Health and Medical Research
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