June 2012 Issue
Gut Health and Immunity — It’s All About the Good Bacteria That Can Help Fight Disease
By Lori Zanteson
Today’s Dietitian
Vol. 14 No. 6 P. 58
The gut is hardly cocktail party conversation, but some
would argue that it’s on its way to becoming just that. Not only is gut
health a popular topic in scientific research, it has a following in
food circles. An understanding of the association between food and the
gut for increased immunity and overall health is gaining momentum, as
is the RD’s role in preventing disease through the promotion of a
gut-healthy diet.
The Basics
Everything we eat and drink passes through the gut along
the gastrointestinal (GI) tract. It seems simple enough, but the
tubelike GI tract, lined with a thin, sticky mucous, is embedded with
millions of bacteria that live, grow, and metabolize (digesting and
absorbing) in what’s considered a complex ecosystem comprised of both
beneficial and harmful bacteria. According to A. Venketeshwer Rao, MSc,
PhD, professor emeritus in the department of nutritional sciences at
the University of Toronto, “It’s the predominance of the beneficial
bacteria referred to as the probiotic bacteria, such as bifidobacteria
and lactic acid bacteria, that ensure good health and prevent diseases
of the gut and other organs in the body.”
Recent evidence, Rao explains, shows a close involvement
of gut microflora and various aspects of health, such as nutritional
status, behavior, and stress response. “[The gut microflora] accomplish
this via several mechanisms,” Rao says, “but primarily by metabolizing
our dietary constituents to either detoxify them or activate them into
toxic forms. A presence of pathogenic bacteria requires a
well-functioning and strong immune system to prevent infections. In
this way, the nature and composition of the gut microflora can
influence our immune system.”
These beneficial probiotic bacteria do several things
that contribute to good health and immunity. As Rao mentioned, their
most basic function is to fight harmful foreign substances that enter
the body by detoxifying them and easing their elimination. Probiotics
can prevent the growth of harmful bacteria, which thrive and grow
within a neutral pH environment, by producing organic acids such as
acetic and lactic acids that, in turn, lower the pH of the large
intestine. This lower pH also prevents the metabolism of cholesterol
and bile acids in the colon. “Since cholesterol and bile metabolites
act as cancer-causing agents,” Rao explains, “they can play an
important role in the prevention of cancers of the GI tract and other
organs as well.” These helpful bacteria, he continues, can even lower
serum cholesterol levels along with cardiovascular disease risk by
preventing the activity of an enzyme involved in the synthesis of
cholesterol.
What Is Gut Health?
While there’s no clear definition of gut health other than
a general absence of disease or GI issues, “Gut Health: A New
Objective in Medicine?” published in the March 2011 issue of BioMed Central Medicine, lists five criteria that provide a positive basis for understanding (see sidebar).1
Intestinal microbiota, or gut flora, and the gut barrier
determine gut health. Inside the gut are about 100 trillion live
microorganisms that promote normal GI function, protect the body from
infection, and regulate metabolism and the mucosal immune system. In
fact, they comprise more than 75% of the immune system. Also important
is their role in maintaining and protecting the GI barrier. An intact
GI barrier maintains gut health, while a problem with its microbiota
composition will affect the body’s defense systems and can create a
condition known as leaky gut syndrome, which can compromise gut health
and lead to diseases such as inflammatory breast cancer, obesity,
chronic fatigue syndrome, and depression.
Maintaining Gut Health
When it comes to gut health, Kathie Madonna Swift, MS, RD, LDN, coauthor of The Inside Tract: Your Good Gut Guide to Digestive Health,
said in the March 21, 2012, webinar “Functional Nutrition and the Gut”
that “diet and nutrition therapy should be the first route [to
obtaining gut health], not the alternative. In Western medicine, they
[prescribe] medicine.” Based on several studies, the current medical
focus is on treatment rather than prevention. Several drugs exist to
treat acute inflammatory bowel disease (IBD), for example, but none to
prevent it.
The research behind what’s known as the hygiene
hypothesis says an imbalance within the gut will impair the gut barrier
and increase risk to gut health and of developing disease. Conditions
that cause imbalance can be an unbalanced diet but also may be lack of
exercise or chronic stress. Recent studies have shown that high dietary
fat and high fructose disturb the GI barrier, which can lead to fatty
liver disease and inflammation.1 On the other hand, positive changes in
the diet have been shown to help prevent major diseases such as
obesity, allergy, and cancer.1 As more research shows the key role that
diet and lifestyle play in maintaining gut health and preventing GI
diseases, including infection, IBD, and food allergies, Swift says, “We
[dietitians] have to be the change agent to make this happen.”
Swift says processed foods and today’s grains vs. ancient
grains have a big impact on gut function. To help improve it and
prevent disease, she counsels clients to feed gut flora by “plant
centering the plate” and eating foods that are nutrient dense, high in
fiber, and have a low glycemic load.
As a proponent of the RD’s role in public health, Rao
agrees. Dietitians would do well to counsel clients to eat
“health-promoting diets and, in particular, diets that help promote the
predominance of the beneficial bacteria,” he says. Because probiotic
bacteria use complex carbohydrates such as dietary fiber and harmful
bacteria use dietary proteins and fats to produce toxins that can
damage good health, Rao suggests a diet that’s a “good source of
complex carbohydrates and low in red meats, which are sources of
protein and saturated lipids. Good food sources of complex
carbohydrates include fruits, vegetables, legumes, and cereals. Another
important recommendation is to include foods that are rich sources of
antioxidants such as fruits and vegetables.”
“Food is central, but supplements can be helpful,”
Swift adds. Most notable in supporting gut health are supplements
containing probiotics or prebiotics. Though the number of studies is
limited, probiotics have been shown to maintain gut health and prevent
chronic bowel diseases such as IBD and restore leaky gut. While it’s
still premature to recommend these supplements as a preventive measure,
current evidence indicates a “strong rationale for using probiotics,
possibly also in synergistic combinations with prebiotics, to maintain
gut health.”1
RDs always have understood and counseled clients on the
importance of food as preventive medicine and a maintainer of overall
health. By recommending a balanced diet, exercise, and strategies to
reduce stress as well as prebiotics and probiotics, RDs can support gut
health in their practice. Now that medical research is beginning to
make that food and gut-health connection, RDs will play a key role in
what will hopefully be a shift in focus from treatment of GI disease to
prevention.
— Lori Zanteson is a southern California-based food and health writer whose work has appeared in various publications.
Reference
1. Bischoff SC. ‘Gut health’: a new objective in medicine? BMC Med. 2011;9:24.
Five Criteria for a Healthy GI Tract1
Specific Signs of Gastrointestinal (GI) Health
• Normal nutritional status and effective absorption of food, water, and minerals
• Regular bowel movement, normal transit time, and no abdominal pain
• Normal stool consistency and rare nausea, vomiting, diarrhea, constipation, and bloating
Absence of GI Illness
• No acid peptic disease, gastroesophageal reflux disease, or other gastric inflammatory disease
• No enzyme deficiencies or carbohydrate intolerances
• No inflammatory bowel disease, celiac disease, or other inflammatory state
• No colorectal or other GI cancer
Normal and Stable Intestinal Microbiota
• No bacterial overgrowth
• Normal composition and vitality of the gut microbiome
• No GI infections or antibiotic-associated diarrhea
Effective Immune Status
• Effective GI barrier function, normal mucus production, and no enhanced bacterial translocation
• Normal levels of immunoglobulin A, normal numbers and normal activity of immune cells
• Immune tolerance and no allergy or mucosal hypersensitivity
Status of Well-Being
• Normal quality of life
• Qi (ch’i), or positive gut feeling
• Balanced serotonin production and normal function of the enteric nervous system
— LZ
No comments:
Post a Comment