Microbes
in our guts? An organ?
One
of the greatest challenges to independent living for the elderly is frailty.
Frailty occurs when our organs and other bits, such as our eyes or hips,
accumulate disorders or just give out. One organ that you would not think would
age is the one that consists of the microorganisms in our gut.
Actually,
there are about ten times more bacteria than human cells in your body. Together
these microbes have over 150 times more genes than you. These microbes, which
occur in your gut, are known as the ‘intestinal microbiota’ or ‘microbiome.’ The
microbiome is so critical in your life that some scientists call it ‘the
forgotten organ,’ or ‘the second brain,’ and the microbiome and the brain are
in constant communication with each other.
Our
mothers contribute the microbes we are born with, and their activity is crucial
in our first days and weeks for development of our immune and neurological
systems. As we age our microbiome
becomes more diverse. Each of us has our own microbial community and while it
changes somewhat through life, it basically remains constant. We get into
trouble when our microbiome is disturbed.
The
microbiome can be a friend or a foe, depending upon on how we maintain its
composition. This depends upon our diet and our physical environment.
The composition of our microbiome is all important. There are millions, billions, of microbes down there. Mainly bacteria but also bacterium-like microbes called archaea, fungi, and even viruses. Some are beneficial or at least neutral while others are pathogens that can do you harm. In the environment of your gut there is constant jockying for dominance. The key is homeostasis, where the good keeps the bad in check. This balance can get out of whack, and when that happens there can be trouble.
The homeostasis of our microbiome is greatly
influenced by our individual menvironment and our diet. To illustrate this, scientists compared the diets and gut microbiomes of a modern-day hunter-gatherer people in Tanzania, the Hazda, to contemporary Italians. The research found a marked difference in
protein and carbohydrate metabolism between the Hazda and the urban Italians. The diet of the Hazda people
consists of 70% plant materials, and this includes many indigestible substrates
that favor microbial diversity and gene action in the gut. In contrast the
urban Italian diet consisted of highly refined sugars and processed foods that favor lower
microbial diversity. Westernized diets comprise cultivated foods that are selected for
palatability and caloric content and are subject to extensive processing for maximal
digestibility. Interestingly, there was a much lower opportunity for horizontal
gene transfer in the Hazda gut microbiome than in the Italian. Horizontal gene
transfer is a process by which traits such as antibiotic resistance are transferred
between organisms. Horizontal gene transfer is considered to be a main cause of antibiotic
resistance and the consequent development of 'super bugs' that cannot be controlled by antibiotics. That western diet of foods that have been cultivated for digestibility and are highly processed seems, indeed, to contribute to an environment that favors the development of bacterial resistance to antibiotics.
In
other studies scientists observed that the incidence of autoimmune diabetes was
much higher in Finnish and Estonian children than in kids living across the
border in Russia. The scientists found sharp differences in the
types of microbes in the guts of the respective groups of kids. While
both microbial gut communities produced endotoxins, the endotoxins in the blood of the
Russian children could excite their immune systems much more strongly than
could the endotoxins in the blood of the
Finnish and Estonian children. The difference could not be explained by breast
feeding but was attributed to an early childhood where the Russian children experienced a greater
exposure to microbes that would stimulate, or ‘educate’ the immune system than the kids in the 'more highly developed' (i.e. sterile) environment of Finland and Estonia.
A
diverse microbiome is essential for good health. A good diet promotes
beneficial microbes while limiting colonization by pathogens. Beneficial microbes produce anti-inflammatory factors,
pain relieving compounds, antioxidants and vitamins. The two-way communication between our brain
and our gut microbes modulates brain development. It possibly plays a role in our
moods. The association of a disturbed microbiome with behavioral and gastrointestinal
manifestations of autism spectrum disorder suggest treatments.
Foods
containing probiotics and prebiotics help us maintain our microbial
communities. A probiotic is a living organism that may improve the health of
the host beyond its inherent nutritional content. Probiotic foods typically
contain lactic acid bacteria that are present in traditionally fermented foods
such as soy products, pickles, sauerkraut, and yoghurt. Many supplements containing
probiotics are available. An important point to consider when purchasing one of the probiotic dietary supplements is that it contain live bacteria.
Prebiotics
are indigestible food ingredients that benefit us by stimulating the growth of
one or a limited number of certain bacteria in the colon. Foods rich in
prebiotics include banana, chocolate, onions, legumes, whole grains and
cabbage.
Probiotics
and prebiotics are features of a ‘Mediterranean-style’ diet. Our Standard
American Diet, high in trans-fat, sugars and highly processed food, only encourages
growth of gut pathogens. In the study cited above, the diet of the Hazda people mainly consists of vegetable material and this is thought to be much closer to the diets of our prehistoric -- or even as recent as early 20th Century -- ancestors.
In the elderly the
microbiome may become diminished due to the general state of health,
malnutrition, a diet low in microbe-accessible carbohydrates, increased use of
antibiotics and pain relievers, and insufficient exercise. One large study revealed
that the microbiomes of nursing home residents were far less diverse than those
of seniors living in the community.
Among the problems experienced by the elderly is lactose intolerance and an inability to digest dairy products. Probiotic lactic acid
bacteria
can treat lactose intolerance. Some studies show that older subjects given
fermented milk had less severe colds and flu, and were quicker to recover than
those who did not get the milk. Other research suggests that probiotics protect
against traveler’s diarrhea, help prevent tooth decay, and reduce the severity
of eczema.
Changes
in the composition of the microbiome in the elderly have been linked with
inflammatory and metabolic disorders, including inflammatory bowel disease,
inflammatory bowel syndrome, obesity, osteoporosis, osteoarthritis, gout and
cardiovascular disease.
A
common problem in the elderly, and antibiotic induced diarrhea, a significant
cause of mortality in the elderly. Fecal
transplants, which is exactly what it sounds like, has been adopted as a
measure to treat antibiotic induced diarrhea that is caused by the bacterium Clostridium difficile. The explanation
for the effectiveness of this seemingly radical, or at least ‘icky,’ procedure
rests in the replacement of a ‘sick’ microbiota, one in which the offending
bacterial species has been allowed to dominate, with one in which there is a
benign, balanced and diverse microbiota.
Other as yet experimental evidence indicates that fecal transplant may
help in the struggle against obesity. Exactly how this all happens, which
microbes are involved, is unknown so there is no pill in sight.
Chronic
fatigue syndrome (CFS), a condition that causes extreme fatigue and the
inability to take part in daily routines, has been considered to be a
psychological problem. Newly developing evidence at least suggests a physical
cause that might be linked to bacteria in the gut. People with CFS had a much
less diverse gut microbiota and much higher levels of inflammatory molecules in
their blood than did healthy people. Researchers were able to identify people
with CFS through diagnosis of their gut bacteria and inflammatory molecules in
their blood in about 80% of the cases. This gives new clues to understanding CFS and to why people
experience these symptoms.
Study of our gut microbes is the object of a very large international research effort. Science has revealed astonishing
roles for our microbiome in our health. With astonishing frequency links between dysfunction of our microbial organ and medical conditions are being revealed. The connection between our gut microbes and our brains through the vagal nervous system has even lead so speciulation about which is the controlling organ! It is all fascinating in a brave new world sort of way, and at least to me, so unexpected. Tantalizing results suggest that fuller
understanding of the human-microbiome connection will soon yield major health
benefits to all.
Meanwhile, eat your yoghurt
and sauerkraut. They are good for your gut microbes!
Beatrice Trumm Hunter
contributed to this article
