Putting Good Bacteria to Work

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Putting Good Bacteria to Work

By JANE E. BRODY

http://www.nytimes.com/2004/09/14/health/14brod.html?pagewanted=all & position

 

Published: September 14, 2004

 

From a cellular perspective, you might think the human body was mostly

human. But you'd be wrong. It is actually mostly bacterial.

 

The typical adult body harbors about 100 trillion bacterial cells from

at least 500 species - 10 times the number of human cells. And that's

not counting viruses and fungi.

 

Most of these bacterial organisms are what medicine calls " friendly, " or

at least harmless. Friendly bacteria, or probiotics, serve a host of

biological functions important to the survival of the animal they

populate. Some aid in digestion, some compete with harmful bacteria and

keep them in check, some stimulate the immune system. And they may have

other roles not yet known.

 

Researchers here and abroad are looking at probiotics as a promising

answer to the growing problem of antibiotic resistance and abuse. To

date, studies have indicated that ingested probiotics can play an

important role in preventing or controlling food and skin allergies in

children, bacterial vaginosis and premature labor in pregnant women,

inflammatory bowel disease, recurrent ear and bladder infections, dental

caries, chronic diarrhea and traveler's diarrhea. They may even help

lower cholesterol in the blood and, by degrading carcinogens, thwart the

development of certain cancers.

 

Bacteria for Life

 

The health potential of probiotics has been known for about 100 years,

but their value has largely gone unrecognized by Western health

professionals. But interest in probiotics has exploded in the last

several years in the face of surging bacterial resistance to many potent

drugs, consumers' demand for natural remedies and accumulating evidence

that some probiotic organisms prevent or treat certain challenging

medical conditions.

 

Probiotics, derived from the Greek phrase " for life, " are defined by the

World Health Organization as " live microorganisms which, when

administered in adequate amounts, confer a health benefit on the host. "

There are three crucial concepts in this definition - " live, "

" microorganisms " and " health benefits. " Contrary to advertisements for

some products, foods themselves are not probiotics, although some, like

fermented milk, can be prepared to contain enough beneficial bacteria to

promote health.

 

Unfortunately, according to one prominent scientist in the field, Dr.

Gregor Reid of the University of Western Ontario, many foods and

supplements now being sold as probiotics are worthless. All too often,

he said, the organisms in them are present in too small a quantity to be

beneficial. Or the products contain species not yet shown in rigorous

studies to benefit health.

 

" Many so-called probiotic products have not been properly identified,

documented, manufactured under good manufacturing practices or proven

clinically, yet various companies make claims that lead consumers and

care givers to believe that they are using reliable products, " Dr. Reid

and colleagues wrote in Clinical Microbiology Reviews last October.

 

What Can They Do?

 

It has become increasingly apparent that the absence of bacteria in the

intestines is unhealthy. For example, laboratory animals raised to be

germ-free are often sickly, with seriously underdeveloped immune systems

and vulnerable intestinal tracts. Such a circumstance would render an

infant susceptible to allergies and life-threatening infections. One of

the best-documented benefits of probiotics has been preventing eczema in

babies with an inherited tendency to develop allergies.

 

For example, in a carefully designed study, researchers in Finland

administered the probiotic Lactobacillus GG to pregnant women and to

their babies who were considered at high risk for developing allergies

for six months after birth. By the time the children were 2, the

probiotic cut the incidence of eczema in half.

 

This organism " has proved safe at an early age and effective in

treatment of allergic inflammation and food allergy, " the researchers

reported in the journal Lancet. The mode of action is believed to

involve the ability of probiotics both to reduce the absorption of

dietary allergens by enhancing intestinal development and to degrade

allergens in the babies' digestive tracts.

 

The human digestive tract is sterile at birth but rapidly acquires

organisms. The first ones to become established dominate the system.

Nowadays, many infants are first colonized by organisms acquired in the

hospital, rather than the beneficial Lactobacilli and Bifidobacteria

that predominated when babies were born at home. Breast-feeding

introduces beneficial bacteria, which may account for the lower

incidence of allergies in breast-fed babies.

 

In another benefit to babies, Dr. Reid, a microbiologist, and his

obstetrical colleague Dr. Alan Bocking have reviewed the ability of

probiotics to prevent premature labor and delivery arising from

bacterial vaginosis. These infections, which often cause no symptoms or

are misdiagnosed as yeast infections, can invade the membranes around

the fetus and stimulate premature labor.

 

The Canadian researchers' studies of two strains of probiotic

Lactobacilli showed that when the organisms were taken by mouth, they

tended to impede the growth and establishment of various harmful

bacteria known to cause intestinal, urinary tract and genital infections

that could invade the womb.

 

In an interview, Dr. Reid described other benefits to children of

probiotic bacteria that have been found in early studies by various

researchers, including fewer respiratory infections and dental caries,

as well as fewer episodes of and quicker recovery from diarrheal diseases.

 

For adults as well as children, some studies have suggested that regular

consumption of probiotics can reduce the chance of contracting

travelers' diarrhea and limit the formation of cholesterol, though not

to the level of statin drugs.

 

In Japan, many people regularly consume a probiotic drink called Yakult,

which has been shown to reduce the recurrence of bladder infections.

Another product, VSL-3, which contains eight different probiotic

organisms and is sold in Italy, may help keep Crohn's disease, a serious

inflammatory bowel disorder, in remission.

 

At the moment, however, the hype about probiotics and the explosion of

untested products in the United States have outstripped the science.

Products must resist stomach acid yet dissolve readily in the

intestines. They must also be protected from air and moisture to remain

viable. If a probiotic product is formed into chewable tablets, the

application of heat will destroy some organisms, so the manufacturer has

to put enough in to have enough left.

 

Many consumers rely on yogurt with active cultures as their source of

probiotics, but the organism most often used in these fermented milk

products, Lactobacillus acidophilus, is not the primary bacterium

naturally found in the gut, Dr. Reid said.

 

Lactobacillus reuteri is a natural inhabitant of the gastrointestinal

tract and is an excellent probiotic. The organism was originally derived

from breast milk and is available in capsule form at pharmacies and

health food stores and on the Internet. Early studies indicate that this

organism can speed a child's recovery from diarrheal disease and is safe

for use in patients with H.I.V., Dr. Reid said.

 

Dr. Reid holds a patent on one probiotic product not yet available in

North America but licensed to Chr. Hansen, a Danish company. That

company sells another product, ProbioTek, that is encapsulated to

survive oral ingestion and reach the intestinal tract, where its

potential protective action can be released. It contains four

microencapsulated probiotic organisms and is currently sold in American

pharmacies as Flora-Q by Bradley Pharmaceuticals.

 

Currently, in Dr. Reid's opinion, " you get what you pay for, and in most

cases you're not getting very much. " Once again, caveat emptor.