Probiotics: "good" bacteria to the rescue?
At least that's the advertising hype.
The truth: some foods with some probiotic bacteria can help some people with some health problems. Which foods? Which probiotics? Which people? Which problems? That's where it starts to get messy. Here's how to sort it out.
Is it worth buying foods that contain "beneficial" bacteria? The answer is complicated, as even industry-friendly experts admit.
"Choosing good probiotic products can be very difficult for consumers," says Mary Ellen Sanders, executive director of the International Scientific Association for Probiotics and Prebiotics, a non-profit collaboration of scientists that is funded in part by probiotic manufacturers.
(Prebiotics are non-digestible food ingredients--inulin, for example--that stimulate the growth or activity of probiotic bacteria.) Among the hurdles:
* Strain matters. "The effects of probiotics are strain-specific," notes Sanders. "Strains can differ in what they do even within the same species." And only a small number of strains have proven benefits.
Which ones? "Unfortunately, you pretty much have to be a Ph.D. in the field to be able to sort through ali the research to find those that are reasonably substantiated," says Sanders.
There are three parts to any bacterium's name: the genus (like Lactobacillus), the species (like acidophilus), and the strain (like LA-5). One L. acidophilus strain doesn't necessarily have the same benefits as another L. acidophilus strain.
"I compare it to being invited to meet George Clooney," says researcher Gregor Reid of the University of Western Ontario in Canada. Is it George Clooney the Holly wood actor or some other George Clooney? "in the same way, you need to know more than the first two parts of a probiotic's name to know what you're getting."
Unfortunately, companies don't have to disclose which strains they put into their foods or supplements.
* Dose matters. You can't tell whether a probiotic will work unless you know how much is in what you're eating or taking. And companies don't have to say.
* Survival matters. A probiotic is useless if it's dead by the time you open the package. "Even if the product has been shown to contain a suitable number of living bacteria on the day it's manufactured," says Reid, "the consumer doesn't know if the bacteria are going to be available at the end of the product's shelf life."
When the supplement-testing Web site consumerlab.com recently analyzed 20 probiotic supplements, only 12 contained the amount of live bacteria listed on the labels. Some had as little as 7 percent of what they were supposed to have.
Here's the evidence for some of the most popular probiotic products.
Claim: "Scientifically proven to help with slow intestinal transit time."
What's in it: Bifidum regularis, Dannon's name for Bifidobacterium animalis DN-173 010.
Evidence: All of the research on Activia and the GI tract has been sponsored by Dannon. In four studies, it took 10 to 30 fewer hours for food to move through the digestive tracts of more than 350 healthy people after they ate 4 to 12 ounces of Activia a day for 10 to 14 days.
Does faster transit time in people with no complaints translate into better regularity in people with occasional complaints? No studies have looked. (In chronically constipated Chinese women, 4 ounces of Activia a day led to one more bowel movement a week. (1) But chronic constipation may have different causes than occasional irregularity.)
Dannon also funded a study to see if Activia could reduce GI symptoms. Among nearly 200 German women aged 18 to 60 who gas, bloating, stomach rumbling, and/or abdominal discomfort, those who ate 8 ounces of Activia every day for four weeks reported less frequent rumbling and flatulence, but no change in discomfort and bloating (and no more frequent bowel movements) than those who consumed a yogurt without Activia's probiotics. (2)
Bottom line: Activia speeds transit time and may help relieve stomach rumbling and gas. However, it's not clear whether it can help with occasional irregularity.
(1) World J. Gastroenterol. 14: 6237, 2008.
(2) Br. J. Nutr. 102: 1654, 2009.
Claim: "YoPlus cultures are clinically proven to help naturally regulate digestive health."
What's in it: Bifidobacterium lactis Bb-12 and inulin. (The inulin is a prebiotic. It provides food for the probiotic Bifido.)
Evidence: Until competitor Dannon complained to the Better Business Bureau in 2008, General Mills advertised that Yoplait YoPlus--not just the probiotic cultures in it--helped with digestion, worked in 10 days, and was comparable to Dannon's Activia.
The BBB's National Advertising Division agreed that General Mills didn't have enough evidence for its claims. The company had never tested YoPlus on digestion. And the only study of Bb-12 in yogurt, in which 30 young Japanese men and women averaged one extra bowel movement during the two weeks they ate 3 1/2 ounces a day of yogurt with Bb-12, was hardly proof that it would do anything for Americans with occasional irregularity.
General Mills eventually funded a study in 36 women and men who complained of bloating, constipation, diarrhea, or other bowel problems. Half were given a YoPlus-like drink every day and half were given a placebo drink. After six weeks, food was moving through the digestive tracts of the probiotic takers about four hours faster than through the placebo takers' digestive tracts.
But the study (which hasn't been published yet) was flawed. The two groups didn't start out with similar transit times, so it's not clear how much of a difference--if any--the YoPlus made.
Last spring, General Mills announced the results of another study (also unpublished). YoPlus improved "overall digestive well being" among men and women who "occasionally experienced symptoms of digestive discomfort," said the company. It provided no details.
Bottom line: There's little published evidence that YoPlus helps with irregularity, digestive discomfort, or anything else.
Claim: "Clinically proven" to "help strengthen your body's defenses."
What's in it: L. casei immunitas, Dannon's name for Lactoba cillus casei DN-114 001.
Evidence: To settle a consumer lawsuit, Dannon has agreed to remove from DanActive's label the word "Immunity" and the claim that the fermented milk drink has a "positive effect" on the immune system.
In the two (Dannon-funded) studies that looked at whether DanActive could keep people from getting sick--mostly with colds or other upper respiratory infections--the drink failed. But it did slightly reduce the time they stayed sick:
* In the first study, researchers gave 1,072 healthy French men and women (average age: 76) either two servings of DanActive or a placebo every day for three months and then monitored them for another month. (1) Over the four months, the DanActive takers were just as likely to get sick--and to get sick just as severely--as the placebo takers. But those in the DanActive group were ill for an average of 7 days during the four months, while the placebo takers were ill for an average of 8 days.
* In the second study, 180 older Italians who drank two servings a day of DanActive for three weeks during the winter were just as likely to get sick as 180 older Italians who didn't drink DanActive. (2) When they did get sick, however, they felt better within 7 days. It took the placebo takers 9 days, on average, to recover.
Bottom line: DanActive won't keep you from getting sick, but might slightly reduce the time you're ill.
(1) Br. J. Nutr. 103: 58, 2010.
(2) J. Nutr. Health Aging 7: 75, 2003.
Claim: For people with "healthy digestive function who are looking for help with occasional digestive upsets or who are interested in promoting their digestive health."
What's in it: Bifidobacterium infantis 35624.
Evidence: Researchers have never tested Align in people with "healthy digestive function." Instead, studies have focused on people with irritable bowel syndrome (IBS). IBS patients suffer abdominal pain, discomfort, bloating, and a change in bowel habits with no apparent physical reason.
In two studies, B. infantis 35624 relieved some abdominal pain and discomfort, bloating, flatulence, and problems with bowel movements. (1,2)
But in a third study, which was funded by Procter & Gamble, Align's manufacturer, 37 people who took Align for eight weeks reported no greater relief in symptoms than 37 similar people who took a placebo. The study hasn't been published yet.
Bottom line: If you have irritable bowel syndrome, Align is worth a try, even though one study showed no benefit.
(1) Gastroenterol. 128: 541, 2005.
(2) Am. J. Gastroenterol. 101:1581, 2006.
Claim: "To maintain or restore healthy vaginal flora that are important in maintaining vaginal health." "To support the health of the urinary tract."
What's in it: Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14.
Evidence: Nearly one in three U.S. women between the ages of 14 and 49 has bacterial vaginosis (BV), though many don't know it. BV increases the risk of becoming infected with some sexually transmitted diseases and of developing pelvic inflammatory disease, which can cause infertility.
"The lactobacilli in the vaginas of women with BV are depleted and replaced with potentially harmful microorganisms," says researcher Gregor Reid. (In 2009 the parent company of Dannon gave Reid a $7 million endowed research chair in Human Microbiology and Probiotics at the University of Western Ontario.)
Reid and a colleague discovered two lactobacilli that can survive the trip through the GI tract and migrate from the rectum to the vagina. Could the bugs restore a healthy balance of bacteria there?
To see, Reid and his colleagues gave 125 Nigerian women diagnosed with BV a seven-day course of the antibiotic metronidazole (Flagyl). The women also received pills with 1 billion L. rhamnosus GR-1 and I billion L. reuteri RC-14 or placebo pills twice a day for 30 days. (1) (A capsule of Fem-dophilus contains 5 billion of the two bacteria combined.) At the end of the trial, 88 percent of the probiotic takers were free of BV, compared with 40 percent of the placebo takers. A similar trial in Brazilian women produced similar results. (2)
"We think the lactobacilli make the pathogenic bacteria in the vagina more vulnerable to the antibiotic by helping to break up a layer that these bacteria form to protect themselves," Reid explains.
Bottom line: An antibiotic plus L. rhamnosus GR-1 and L. reuteri RC-14 may help treat vaginal infections. No good studies have looked at Fem-dophilus and urinary tract infections.
(1) Microbes Infect. 8: 1450, 2006.
(2) Can. J. Microbiol. 55: 133, 2009.
Yogurt is made by adding two probiotic bacteria (Lactobacillus bulgaricus and Streptococcus thermophilus) to milk. The bacteria break down the milk's sugar (lactose) into lactic acid, which makes the yogurt more digestible for people with lactose intolerance.
Many people believe that the bugs also can replenish your gut with healthy bacteria after you take antibiotics and can prevent vaginal yeast infections. But the evidence is scant.
* Antibiotics. To change the balance of bacteria in the large intestine, probiotic bacteria first have to survive the strong acid of the stomach and the bile salts of the small intestine. In a French study in adults who ate yogurt twice a day for a week, L. bulgaricus survived passage through the gut in only 13 of 20 people and S. thermophilus made it through in just I of 20. (1)
What about eating yogurt to prevent the diarrhea and abdominal pain that antibiotics sometimes cause?
In the only study to look at commercial yogurt in generally healthy people, researchers in the UK gave 118 children and adults strawberry yogurt that contained I billion bacteria every day during the week they took an antibiotic and for five days after. Another 120 got just the antibiotic. (2)
"Eating yogurt while taking antibiotics did not prevent antibiotic-associated diarrhea," the researchers concluded. However, among those aged 60 and older, yogurt eaters reported less flatulence and abdominal pain than those who got just the antibiotic. It's possible that the yogurt eaters felt better because they expected the yogurt to help.
* Yeast Infections. The Web site of the National Yogurt Association cites a small study in which a yogurt with L. acidophilus LA-5 lowered the risk of recurrent vaginal candida infections. (3) But there was no placebo group, so the results can't be trusted.
(1) Appl. Environ. Microbiol. 72: 5113, 2006.
(2) Br. J. Gen. Pract. 57: 953, 2007.
(3) Ann. Intern. Med. 116: 353,1992.
Bigelow Probiotics Tea
Claims: "Aids the digestion." "Supports healthy digestion."
What's in it: GanedenBC30, the trademarked name for Bacillus coagulans GBI-30, 6086.
Evidence: Only two small studies--both funded by the company that holds the patent and trademark for GanedenBC30--have looked at the probiotic's impact on digestion:
* Every day for two months, 44 men and women diagnosed with irritable bowel syndrome with diarrhea were given either a placebo or a capsule with about three times the GanedenBC30 in a Bigelow tea bag. (1) Both groups reported roughly the same "very mild" to "mild" abdominal pain and bloating. (The researchers didn't ask the participants about diarrhea.)
* Sixty-one men and women--most of them living in the Dominican Republic--who complained of gas, bloating, or stomach pain after meals were given capsules containing either a placebo or eight times the GanedenBC30 in a Bigelow tea bag every day. (2) After four weeks, the probiotic takers reported slightly less pain, but were just as likely as the placebo takers to have gas or bloating.
Bottom line: Bigelow Probiotics Tea is unlikely to do much to aid digestion.
(1) Postgrad. Med. 121: 119, 2009.
(2) BMC Gastroenterology 9: 85, 2009.
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|Title Annotation:||SPECIAL FEATURE|
|Publication:||Nutrition Action Healthletter|
|Date:||Apr 1, 2010|
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