Good bugs getting more notice

As you read this, your intestinal tract is playing host to a multitude of guests -- several trillion bacteria, between 500 and 1,000 different strains.

But there's no need to rush off to the emergency room: This throng of tiny creatures, which together can weigh more than 4 pounds, exists in every human on the planet.


They perform a variety of useful tasks that our own bodies cannot. They keep harmful bacteria in check, help regulate the immune system and even make vitamin K, a key blood-clotting agent.

"We need bacteria. They do a lot for us," says gastroenterologist Jeffry Katz, a professor at Case Western Reserve University School of Medicine.


Until recently, few researchers studied this complex internal ecosystem. But over the past five years, scientists have taken a closer look, and they're finding that some of these bugs may be able to prevent or treat a variety of ailments, including intestinal disorders, allergies and perhaps even some cancers.

"It's an extremely exciting area. We can exploit the bacteria within the intestine for beneficial purposes," said Dr. Fergus Shanahan, a leading researcher on "probiotics," as these bacterial treatments are known.

Gulping bacteria to improve health is hardly new. People have been eating yogurt -- milk fermented with bacteria -- for centuries. But recent research could lead to a range of specific probiotic treatments.

Some say probiotics can help offset the overly sanitized nature of modern society. This "hygiene hypothesis" argues that our rush to eliminate deadly microbes has also eliminated too many useful bacteria, inadvertently increasing the incidence of ailments they once held in check.

Much of the research has focused on intestinal illnesses, including Inflammatory Bowel Disease. Many probiotics researchers suspect that a disturbance to the intestinal ecosystem results in an excess of harmful, damaging bacteria.

Some scientists believe that adding "good" bacteria to the intestine can counter the harmful bugs. In a small study, University of Chicago gastroenterologist Stefano Guandalini gave daily doses of Lactobacillus GG, a particularly friendly strain, to children with Crohn's disease, an IBD that afflicts 500,000 Americans. Their symptoms improved markedly.

"The good bacteria seem to have a protective role," said Guandalini, who is now doing a larger follow-up study.

Other scientists are examining whether probiotics can treat allergies and other immune system ailments. Finnish researcher Erika Isolauri gave Lactobacillus GG to pregnant mothers and then to their newborn infants. Compared with a control group, these babies had half the rate of atopic dermatitis, a common skin rash.


Perhaps most intriguing, researchers are accumulating evidence that probiotics can help prevent colon cancer, which kills around 50,000 Americans a year. Irish researcher Ian Rowland has found that several microbes prevent precancerous cells from forming in mice.

No one knows how beneficial strains like Lactobacillus GG actually work. They may produce natural antibiotics that kill destructive bacteria, strengthen the intestinal lining or occupy key intestinal receptor sites, crowding out other microbes.

"The intestinal milieu is remarkably complex and difficult to study," said Katz, who suspects that most gut bacteria have not even been discovered yet.

Advances in genetics are making the job easier. In the past, many of these bacteria couldn't survive outside the intestine, and so couldn't be cultured in the lab. But researchers can now use DNA from dead organisms to identify new species.

Some researchers have moved beyond identifying helpful bacteria, and are trying to genetically engineer these microbes to make drugs or perform other useful tasks.

Bacteria are relatively simple creatures, so adjusting their genetic makeup presents fewer difficulties. And because bacteria are already adapted to the human body, they are unlikely to be destroyed before completing their assigned task.


This approach has already shown promise. Stanford researchers have engineered a lactobacillus to latch onto and kill the HIV virus. The bacteria live naturally in the human vaginal tract; if the modifications turn out to be safe for humans, the modified version could be the basis of an affordable HIV vaccine.

Even without definitive evidence that probiotics work, some doctors have begun recommending bacterial remedies. For the past five years, Dr. James George, a gastroenterologist at Mount Sinai Hospital in New York, has advised many patients to take probiotics for irritable bowel syndrome, a chronic condition that causes abdominal pain and diarrhea. Bacteria help a "substantial portion" of those who take them, he says.

Although proponents like George are an exception in the United States, probiotics are well-known and commonly used in Europe and Japan. In fact, they are a billion-dollar industry, available in mainstream stores and supermarkets.

In the United States, by contrast, such products are generally available only in health food stores or via the Internet.

"The concept that microbes could be good for you is foreign to people in this country," said microbiologist Mary Ellen Sanders, president of the International Scientific Association for Probiotics and Prebiotics. The nonprofit group was formed in 2002 to bring scientific rigor to a field that even bacterial believers admit sometimes veers into snake oil territory.

Because the U.S. Food and Drug Administration classifies probiotics as foods and supplements rather than drugs, the industry receives little oversight. Some manufacturers take advantage of this: One company, for example, sells a "probiotic" after-shave. Katz recently analyzed 17 probiotic products and found that more than half contained far less bacteria than advertised.


"There are a lot of outrageous claims that have not been subjected to testing," added Shanahan, who is director of the Alimentary Pharmabiotic Centre at the University of Cork in Ireland. He worries that shoddy or overhyped products could taint the entire field.

Shanahan, who began studying probiotics 20 years ago, came to the field as a skeptic, expecting to find that probiotics had little or no benefit. Instead, he has been convinced of the opposite. "There are too many observations here that are real," he said. "We need to explore this."