Beneficial Bowel Bacteria – Our Neglected Friends
John McDougall, MD
http://www.drmcdougall.com
My guess is the welfare of the bacteria living in our
colons was not a topic for discussion at your last social gathering – but
that may change. Within our intestines live trillions of organisms that
are so important to our health and survival that they should be thought of
as a vital organ – just like our livers or kidneys. The gut microflora is
the name we give to this living factory, whose beneficial functions
include: completing the digestion of our foods through fermentation,
protecting us against disease-causing microbes, synthesizing water soluble
vitamins, and stimulating development and function of our immune systems.1
Most people think of bacteria as dangerous and dirty. In
truth, the vast majority of organisms living in this microscopic world is
helpful, or at least not harmful, to our lives. Our intestinal tracts
contain a complex and diverse society of disease-causing (pathogenic) and
“friendly” bacteria. Rule number one is simple: dominance by the “good
guys” will crowd out and leave no room in our intestines for the harmful
ones. In addition to digesting remnants of our meals and synthesizing
vitamins, the helpful bacteria play an important role in the development
of the immune system by maintaining a constant dialog with our internal
bodies through the surface of the gut. Our microflora also influences many
of our hormones. The health consequences from an imbalance of our sex
hormones can lead to precocious puberty, fibrocystic breast disease, PMS,
uterine fibroids, prostate enlargement, and breast, uterine, and prostate
cancer. When our bowel bacteria really get out of control severe forms of
colitis and colon cancer can be the consequences.
The Microbial Factory
Bacteria are not distributed randomly throughout the
intestinal tract, but are found in different numbers and kinds in
different regions of the gut. The mouth provides a fertile garden for
millions of bacteria; but the stomach, because of the acid, and small
intestine contain very low numbers. The final five feet of the intestine,
known as the large intestine or colon, works as a microbial factory with
more than 500 different species of bacteria living in a 3 pound (1.5 Kg)
mass of partially digested matter. Within the colon the concentration of
bacteria reaches 1,000,000,000,000 (one trillion) organisms per gram
(1/30th of an ounce) of feces. Bacteria make up about 60% of the weight of
the feces. The microflora are so important to our well-being that after a
person’s colon is surgically removed (colectomy), the last part of the
small intestine (ilium) takes over this vital role and becomes colonized
with a similar biomass of bacteria.2
The health of the flora can become impaired by
temperature, illnesses, antibiotics and other drug treatments, and changes
in our diets. The effects of antibiotic therapy can be profound and
persistent, even causing a life-threatening infection with overgrowth of
pathogenic bacteria (called Clostridium difficile).
Benefits of a Healthy Gut Microflora
Increase the natural resistance to infections from
bacteria, yeast, and viruses
Prevent traveler’s diarrhea
Speed healing from diarrheal diseases and relapsing
colitis
Improve digestion
Relieve constipation
Stimulate the immune system
Lessen symptoms of inflammatory arthritis
Suppress cancer development and growth
Reduce sex hormones
Reduce cholesterol and triglycerides
Colonization Begins with the Newborn
Before birth the gastrointestinal tract of a normal
fetus is sterile. During the birth process the newborn is inoculated, by
passage through the birth canal, with organisms from the mother’s vagina
and bowel.3 Benefits to the infant begin immediately with this natural
defense barrier of “friendly” bacteria standing against harmful microbes
that will enter later on with touching, suckling, kissing, and caressing.
The importance of this early invasion should not be underestimated. This
initial invasion makes a permanent impression on our immune systems,
thereby affecting a person’s well-being throughout his or her life.
Newborns delivered by cesarean section do not get a healthy dose of
mother’s bacteria. Born through the abdomen, much of their initial
bacteria come from the unhygienic environment of a hospital. However, this
setback can be remedied by the initiation of proper infant feeding after
birth – and helped by the addition of infant probiotics (see below).
Breast feeding encourages the growth of “friendly”
bacteria known as Bifidobacterium. These vital organisms protect the baby
from gastrointestinal infections that can result in illnesses severe
enough to require hospitalization, and sometimes cause death. Mother’s
milk contains sugars (galacto-oligosaccharides) which encourage the growth
of these friendly bacteria. By the fourth day of life, Bifidobacterium
represent 48% of the bacteria in breast-fed infants as opposed to 15% in
bottle-fed infants.4 Eventually, over 95% of the bacteria become
Bifidobacterium bacteria in an exclusively breast-fed baby. Introduction
of small amounts of formula to a breast-fed baby will result in shifts
from a breast-fed to a formula-fed pattern of the microflora. After
weaning from breast milk – ideally after the age of 2 years – the child’s
flora become similar to an adult’s.
Change the Diet – Change the Microflora
The partially digested remnants of our meals, after
arrival in our large intestines, become the foods for our microflora. Each
species of bacteria survives best on specific kinds of nutrients. In
short, “friendly” bacteria prefer to dine on plant-food remnants, and
pathogens thrive when the diet is low in plant foods and high in meat and
other “junk-food.” Therefore, what we choose to eat determines the
predominance of the bacteria species that will live in our gut. By
changing from a diet based on animal- and highly processed-foods to whole
plant-foods, you can suppress the growth of harmful bacteria and stimulate
those that are beneficial. Major alterations in the microflora take place
within one to two weeks of changing a person’s diet.5
Bacteria enjoy the parts of the plant foods that we
don’t use. Undigestible complex carbohydrates, known as dietary fiber, and
other smaller undigestible sugars, called oligosaccharides, provide the
bulk of the food for our bowel bacteria. Only plants contain these complex
and simple carbohydrates (except for milk as above). The undigestible
simple sugars are abundant in artichokes, onions, chicory, garlic, leeks,
and to a lesser extent, cereals. Beans, peas, and lentils contain the
oligosaccharides, raffinose and stachyose, that feed our bowel bacteria
and, quite noticeably, form the infamous flatus. Purified wood cellulose,
which has been used to manufacture some “high-fiber breads,” is not broken
down by the microflora. Because only plants contain these microflora-nourishing
sugars, strict vegetarians (vegans) have been found to harbor much higher
counts of “friendly” bacteria than do meat eaters.6,7
Manipulating Our Microflora with Probiotic Supplements
Purposefully adding particular species of bacteria has
the potential of rebalancing the intestines and thereby improving a
person’s health. Probiotics are used for this purpose and are sold as
foods and pills (supplements) that contain millions of friendly bacteria,
and sometimes yeast. Probiotics can be purchased in the natural food
stores – they are usually found in the refrigerated section; some are
labeled as “newborn formulas” and others are sold for improving the flora
of a child or adult. Probiotics have no toxic effects. Scientific research
has discovered specific species of bacteria must be used in order to
achieve specific benefits when treating health problems.
Conditions Helped by Specific Probiotics8-14
Used as single agents or in combinations
Dental Caries:
Lactobacillus rhamnosus (GG)
H. Pylori (stomach ulcer):
Lactobacillus johnsonii
Lactobacillus paracasei
Acute and Chronic Diarrhea:
Lactobacillus acidophilus
Lactobacillus casei
Lactobacillus reuteri
Lactobacillus rhamnosus (GG)
Bifidobacteria bifidum
Irritable Bowel Syndrome:
Lactobacillus acidophilus
Lactobacillus plantarum
Lactose Intolerance:
Lactobacillus acidophilus
Lactobacillus bulgaricus
Bifidobacteria longum
Constipation:
Lactobacillus casei
Lactobacillus reuteri
Lactobacillus rhamnosus (GG)
Bifidobacteria animals
Saccharomyces cerevisiae (yeast)Propionibacterium
freudenreichii
Crohn’s Disease:
Lactobacillus rhamnosus (GG)Saccharomyces boulardii
Escherichia coli, Nissle strain (1917)
Ulcerative Colitis:
Escherichia coli, Nissle strain (1917)
BIFICO (3 Bifidobacteria species)
Saccharomyces boulardii
VLS 3 brand (Lactobacillus and Bifidobacteria)
Diverticular Disease of Colon:
Escherichia coli, Nissle strain (1917)
Vaginal Candida:
Lactobacillus acidophilus
Lactobacillus rhamnosus (GG)
Lactobacillus fermentum
Elevated Cholesterol:
Lactobacillus acidophilus
Lactobacillus bulgaricus
Lactobacillus plantarum
Streptococcus thermophilus
Enterococcus faecium
Elevated Blood Sugar (Diabetes):
Saccharomyces cerevisiae (yeast)
Rheumatoid Arthritis:
Lactobacillus rhamnosus (GG)
Eczema (atopic dermatis):
Bifidobacteria lactis
Streptococcus thermophilus
Lactobacillus rhamnosus (GG)
Premenstrual Syndrome:
Saccharomyces cerevisiae (yeast)
General Immunity:
Lactobacillus plantarum
Lactobacillus johnsonii
Lactobacillus rhamnosus
Bifidobacteria lactis
Bifidobacteria bifidum
Escherichia coli, Nissle strain (1917)
Growth or Weight of Infants:
Bifidobacteria bifidum
Bifidobacteria breve
Streptococcus thermophilus
Colon Cancer Prevention
Bifidobacterium
Prebiotics and Synbiotics
Prebiotics are nondigestible simple sugars
(oligosaccharides) sold as pills and liquids that stimulate the growth
and/or activity of “friendly” bacteria already present in our intestines.
Prebiotics are very effective for relieving constipation, and hold some
promise for the prevention of gallstones and for the treatment of
inflammatory bowel diseases. Examples of undigestible sugars used as
prebiotics are: FOS (fructooligosaccharides), GOS (galactooligosaccharides),
inulin (not insulin), lactulose, and lactitol. Two prebiotics prescribed
by doctors, lactulose and lactitol, have been effectively used to treat
patients with liver failure (hepatic encephalopathy).5 They may also be
helpful in the prevention of colon cancer.13,14
These commercial products have no toxic effects. They
can act as a mild laxative in small amounts, but may produce flatulence
when consumed in large amounts. Combining probiotics (the bacteria) with
prebiotics (the bacteria’s food) results in a logical partnership, called
synbiotics. You will most often find synbiotic products sold as mixtures
of bacteria with FOS. Because the McDougall diet is made of starches,
vegetables and fruits which contain a wide variety of undigestible sugars
that feed and stimulate the growth of “friendly” bacteria, people
consuming such a diet require no additional prebiotics to obtain optimal
health benefits form their microflora (natural or enhanced by probiotics).
Dairy as a Probiotic Source
The best known examples of food with probiotics are
yogurts containing lactic acid-producing bacteria, called Lactobacillus
bulgaricus. These organisms are non-toxic and survive passage through the
intestine. However, they cannot live and reproduce in the colon (they do
not colonize the colon); therefore, they must be ingested regularly for
any health promoting properties to persist. I do not recommend yogurt as a
source of friendly bacteria for two reasons. First, these bacteria’s
beneficial effects have not been conclusively proven.15 More importantly,
yogurt brings with it all the negative qualities of dairy products: high
in fat and cholesterol, allergy producing dairy proteins, and infection
with harmful viruses and bacteria. (See my May 2003 newsletter article
“Marketing Milk and Disease.”) Acidophilus milk is made by culturing milk
with Lactobacillus acidophilus bacteria and has similar drawbacks.16 Any
benefits provided by any species of Lactobacillus can be obtained much
more safely and effectively in supplement forms (pills), avoiding the
health risks of dairy products.
Who Should Alter Their Gut Bacteria?
Everyone should encourage the growth of a healthy
microflora by eating the right foods, and avoiding antibiotics, whenever
possible. This means a “breast milk diet” for infants and a healthy pure
vegetarian diet (like the McDougall diet) for children and adults.
Newborns, delivered by cesarean section, and bottle-fed babies may benefit
from probiotics specifically designed for infant use. Probiotics may be
warranted after a course of prescribed antibiotics in order to help
reestablish a healthy gut flora. Lastly, if, after doing all you can for
yourself with a healthy diet and lifestyle, you still suffer from
unresolved problems, such as irregular bowel movements, indigestion,
elevated cholesterol, or arthritis, then you may want to try enhancing the
activity of your microflora with these kinds of supplements. You have
little to lose – there are no undesirable side effects and the costs are
minimal. You have everything to gain with the probability of improved
health thanks to your always working factory of “friendly” microflora.
References:
1) Guarner F, Malagelada JR. Gut flora in health and
disease. Lancet. 2003 Feb 8;361(9356):512-9.
2) Christl SU, Scheppach W. Metabolic consequences of
total colectomy. Scand J Gastroenterol Suppl. 1997;222:20-4.
3) Mackie RI, Sghir A, Gaskins HR. Developmental
microbial ecology of the neonatal gastrointestinal tract. Am J Clin Nutr.
1999 May;69(5):1035S-1045S.
4) Rubaltelli FF, Biadaioli R, Pecile P, Nicoletti P.
Intestinal flora in breast- and bottle-fed infants. J Perinat Med.
1998;26(3):186-91.
5) Peltonen R, Ling WH, Hanninen O, Eerola E. An
uncooked vegan diet shifts the profile of human fecal microflora:
computerized analysis of direct stool sample gas-liquid chromatography
profiles of bacterial cellular fatty acids. Appl Environ Microbiol. 1992
Nov;58(11):3660-6.
6) Reddy BS, Weisburger JH, Wynder EL. Effects of high
risk and low risk diets for colon carcinogenesis on fecal microflora and
steroids in man. J Nutr. 1975 Jul;105(7):878-84.
7) Toivanen P, Eerola E. A vegan diet changes the
intestinal flora. Rheumatology (Oxford). 2002 Aug;41(8):950-1.
8) Montrose DC, Floch MH. Probiotics used in human
studies. J Clin Gastroenterol. 2005 Jul;39(6):469-84.
9) Fedorak RN, Madsen KL. Probiotics and prebiotics in
gastrointestinal disorders. Curr Opin Gastroenterol. 2004 Mar;20(2)146-55.
10) Salminen SJ, Gueimonde M, Isolauri E. Probiotics
that modify disease risk. J Nutr. 2005 May;135(5):1294-8.
11) Sartor RB. Probiotic therapy of intestinal
inflammation and infections. Curr Opin Gastroenterol. 2005
Jan;21(1):44-50.
12) Peltonen R, Nenonen M, Helve T, Hanninen O, Toivanen
P, Eerola E. Faecal microbial flora and disease activity in rheumatoid
arthritis during a vegan diet. Br J Rheumatol. 1997 Jan;36(1):64-8.
13) Reddy BS. Prevention of colon cancer by pre- and
probiotics: evidence from laboratory studies. Br J Nutr. 1998
Oct;80(4):S219-23.
14) Buddington RK, Williams CH, Chen SC, Witherly SA.
Dietary supplement of neosugar alters the fecal flora and decreases
activities of some reductive enzymes in human subjects. Am J Clin Nutr.
1996 May;63(5):709-16.
15) Adolfsson O, Meydani SN, Russell RM. Yogurt and gut
function. Am J Clin Nutr. 2004 Aug;80(2):245-56.
16) Wheeler JG, Shema SJ, Bogle ML, Shirrell MA, Burks
AW, Pittler A, Helm RM. Immune and clinical impact of Lactobacillus
acidophilus on asthma. Ann Allergy Asthma Immunol. 1997 Sep;79(3):229-33.
©2005 John McDougall All Rights Reserved
Fair Use Notice: This document may contain copyrighted material whose
use has not been specifically authorized by the copyright owners.
We believe that this not-for-profit, educational
use on the Web constitutes a fair use of the copyrighted material (as
provided for in section 107 of the US Copyright Law). If you wish to use
this copyrighted material for purposes of your own that go beyond fair
use, you must obtain permission from the copyright owner.
