Probiotics can help prevent dangerous infections

Hospital patients and people taking antibiotics might benefit from the good bacteria in yogurt and some supplements

Published: October 2013

A serious infection that has been on the rise in hospital patients is now being increasingly reported among people who work or spend time in health care settings, such as a doctor’s office or clinic. Caused by the bacterium Clostridium difficile, also known as C. diff, the infection can cause chronic diarrhea, abdominal pain, and intestinal inflammation, which in severe cases can be life-threatening.

The problem often affects hospitalized patients treated with antibiotics, which not only kill harmful bacteria but also can destroy protective ones, allowing C. diff to gain a foothold. But new research suggests that the bugs are now also infecting people outside hospital settings, including some who haven’t taken antibiotics. In a study of 984 people with C. diff published online June 17 in JAMA Internal Medicine, about 60 percent had taken antibiotics within the previous 12 weeks—but more than 80 percent had been to some type of health care clinic.

While the odds of contracting a C. diff infection are low overall (about 1 in 100 for someone admitted to a hospital, and much lower for others), the consequences can be serious. That’s especially true because the bacterium has been evolving into increasingly virulent strains that can resist drug treatment.

So how can you protect yourself from this threat? Research is finding that the answer might lie in probiotics—helpful bacteria that live in the human gut. A growing body of evidence suggests that those tril­­lions of microorganisms play a critical role in defending us from illness, and that taking supplemental doses of probiotics might help prevent infections like C. diff by restoring the balance of “good bugs” in the gut.

In an analysis of 23 clinical trials by the independent Cochrane Collaboration that was published May 31, 2013, the authors found that taking supplements of probiotics reduced the risk of antibiotic-related C. diff diarrhea by 64 percent. For every 1,000 people in the studies, there were 20 cases of C. diff diarrhea among the patients treated with probiotics compared with 55 cases in the control groups.

The Cochrane findings echo those of a review of 82 studies published in the May 9, 2012, issue of JAMA. It found that taking a probiotic with an antibiotic reduced the risk of developing antibiotic-associated diarrhea by 42 percent compared with taking an antibiotic alone. In 14 studies that looked specifically at C. diff diarrhea, the risk was reduced by 71 percent. (Read more about the the risk of overusing antibiotics.)

Helpful bacteria

Found in pills, powders, and fermented foods such as yogurt and kefir, probi­otics are often said to help “balance” our internal microbial communities, or microbiome, by providing an infusion of health-promoting bugs that support the body’s optimal functioning. Boosts may be especially important at times when our native bacteria are under assault from antibiotics.

Disruptions to our microbiome have been linked to everything from obesity to anxiety to heart disease in lab animals. But while probiotics are sometimes touted for those and other ailments, there’s little evidence that they can help treat them. The strongest studies of probiotics have instead focused on their role in immunity.

Studies have shown there are 10 times more bacterial cells than there are “human” cells living in our bodies, most of them concentrated in the intestines. Those bacteria help digest our food and synthesize vitamins. They also help fortify our defenses against germs that can cause infections.

“If your body is properly colonized, and the appropriate microbes are there, pathogens have a harder time getting a foothold,” said Mary Ellen Sanders, Ph.D., who consults with food and supplement manufacturers on the science and regulatory issues of probiotics.

Scientists speculate that our increasingly sterile environment may be weakening this microbial shield. Our homes are more hygienic and we have less contact with bacteria-laden soil and animals than our ancestors did. Our food and water are also treated in ways that reduce microscopic freeloaders. These developments have no doubt reduced our exposure to potentially dangerous microorganisms, but they may also be limiting the microbial diversity that helps keep our immune defenses humming.

Perhaps the biggest threat to our microbiome, though, is our reliance on antibiotics. Those drugs are prized for their ability to treat infections caused by bacteria. Unfortunately, they often kill helpful bacteria along with harmful ones. Limited evidence has documented a precipitous drop in the diversity of bacteria collected from a patient’s stool sample after a round of antibiotics. It’s possible that these vital microbial communities may not recover for months after a course of antibiotic treatment ends.

That disruption is a key cause of the diarrhea that afflicts up to 30 percent of patients who take antibiotics. In most cases, symptoms are mild and clear up soon after the person stops taking the medication. But about 20 percent of patients with antibiotic-related diarrhea are infected by C. diff, which lurks in hospitals and most frequently affects older adults in poorer health. Every year about 300,000 hos­pitalized patients in the U.S. acquire a C. diff infection, and about 14,000 people die from it.

The probiotics cure?

Based on those findings, many experts, such as Sydne Newberry, Ph.D., who co-authored the JAMA analysis, say that a probiotic might help and probably won’t hurt whenever an antibiotic is prescribed. But other experts, including Mark H. Wilcox, M.D., who leads an effort by Public Health England, a government health agency, to control C. diff infections, think that more evidence is needed before probiotics can be routinely recommended across the board. Wilcox says that the Cochrane analysis showed a benefit only by adding up the results of “small, underpowered studies” that tested a variety of probiotic organisms administered at dif­ferent doses. Although the results point in a positive direction for probiotics in general, he says they don’t provide any insight into which probiotic strains we should be taking.

Newberry, who reviews scientific evi­dence for the Rand Corporation, a nonprofit research institute, agrees that it’s not clear which probiotic, or combination of probiotics, is effective. She noted that in many studies, researchers used their own mixtures of probiotics, which are not available commercially. Other studies did not specify which strain of bacteria they were using.  

“At this point, the literature just isn’t good enough to pinpoint what’s working or why,” she said. Still, she said the potential benefits and low risk justify recommending them to people taking antibiotics.

Other infections

Evidence is strong that taking the pro­biotic Lactobacillus rhamnosus GG reduces the duration of acute infectious diarrhea in children by about a day. Additional infection-related applications of probiotics are considered promising but unproved. For example, some studies have reported reduced rates of respiratory infections, including the common cold, in healthy adults and children taking probiotics. But those studies aren’t rigorous enough to support strong conclusions about effectiveness.

The evidence also is inconclusive about whether probiotics are useful for preventing traveler’s diarrhea, which can afflict visitors to developing countries, or eradicating Helicobacter pylori bacterium, a major cause of peptic ulcers. (Probiotics do seem to help reduce the stomach side effects of antibiotic ther­apy for H. pylori infection.)

In intensive-care units, where patients are at increased risk for a variety of infections, studies have shown that probiotics are helpful in preventing pneumonia in critically ill individuals connected to mechanical breathing machines. But in another study, patients with severe inflammation of the pancreas were more likely to have multiple organ failures or to die when they were given probiotics.

So it’s crucial to consult a doctor before taking probiotics if you’ve been seriously ill. They might cause harm if your immune system isn’t functioning properly due to disease or drug treatments. In very rare cases, probiotic bacteria and yeasts have actually been shown to cause serious infections of the blood or major organs. But they’re considered safe for people who are in reasonably good health.

Consumer Reports says: There are important gaps in the evidence, but studies suggest that probiotics could be an effective precaution against the development of antibiotic-associated diarrhea, including cases that are caused by C. diff. Consider taking a probiotic, such as a live-culture yogurt or a supplement (see the box below), whenever you are prescribed antibiotics for more than just a few days—especially if two antibiotics are prescribed simultaneously or if you are switched from one antibiotic to another during the course of an illness

Though the evidence is weak, some experts say that probiotics are worth a try in other risky situations, such as when taking a cruise or visiting a developing country, both of which may increase your chances of coming down with a nasty stomach ailment.

Finally, you might consider asking your doctor about taking probiotics before being admitted to a hospital, where potentially harmful bacteria may be lurking. To make sure you can safely take them, be certain to discuss your health history and any symp­toms you may be having. And never use probiotics as a substitute for medical care.  

What to look for when choosing a probiotic

Scientists use the term “probiotics” to describe live microbes that have been tested in human studies and found to provide a health benefit. But the Food and Drug Administration doesn’t regulate the use of the term, and marketers use it liberally, sometimes to describe products that haven’t been thoroughly researched.

To tell if a product is truly a probiotic, you might need to check product websites to see if the claims are backed up by results from actual studies. Here are some other things to look for on the product label.

• Strain. A probiotic is defined by its genus (e.g. Lactobacillus), species (e.g. rhamnosus), and strain designation (often a combination of letters or numbers, such as “GG”). In studies of antibiotic-associated diarrhea, researchers used a variety of Lactobacillus species and strains, and the yeast Saccharomyces boulardii. These organisms can be found in many probiotic foods and supplements, including DanActive dairy drink, and pills and packets of powder with the brand names BioK Plus, Culturelle, Florastor, and VSL#3. 

• Dose. Probiotics are measured in colony forming units, or CFUs. Different probiotics have been found to be effective at different levels, and it’s not possible to provide a one-size-fits-all recommendation. To prevent antibiotic-associated diarrhea, taking 10 billion CFUs per day might be more effective than taking a lower dose. In most probiotic studies, patients started taking one at the same time as an antibiotic and continued with the treatment for up to two weeks after the antibiotic was stopped. Probiotic yogurt, powders, and pills should work equally well if they contain an effective dose of the right strains. 

• Manufacturer. Probiotics are regulated as foods or dietary supplements in the U.S., which means they aren’t scrutinized as closely as prescription and over-the-counter drugs and don’t have to meet the same standards for effectiveness. Studies have shown that some probiotic products might not contain the dose of the organisms listed on the label, or that they might contain bacteria that aren’t listed. A reputable company should include an expiration date for the dosage of live bacteria on the label. It should also provide storage instructions, including refrigeration.  

Editor's Note:

This article appeared in the October 2013 issue of Consumer Reports on Health.

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