Can probiotics—the good-for-you bacteria and yeast in some foods and supplements—relieve GI distress, replenish your intestinal flora when you take antibiotics, and keep you from catching a cold?
It all depends on what you’re taking for what.
“About 30 years ago, the GI tract, with its microflora of bacteria, was like a black box,” says researcher Lynne McFarland, an associate professor at the University of Washington Medical Center.
“We weren’t even aware of most of the microbes in there because they don’t grow in a petri dish, which was the only way available then to identify them.”
Today, scientists can easily identify bacteria from fragments of their DNA. And what they’re uncovering is a vast, largely unexplored world that may play a critical role in the body. Among other things, our gut bacteria help digest fiber and synthesize vitamin K. Some even secrete antibacterial compounds that can attack nasty bugs.
Here are four things you may not know about the bacterial world in your intestines, and about the probiotics that many people take to reinforce those bugs:
1. It’s enormous. The collection of microorganisms in the gut—our microbiome—seems unimaginably large. By some estimates, as many as 500 to 1,000 species of bacteria inhabit our intestines, and the roughly 100 trillion microorganisms in those species are around 10 times greater than the number of cells in our body.
We don’t start out that way. When we’re born, our GI tract is sterile. But it immediately begins to be colonized by bacteria from the environment.
“This process doesn’t stabilize until we’re about three years of age and start to eat an adult diet,” notes Tiffany Weir, an assistant professor of food science and human nutrition at Colorado State University. From childhood on, your microbiome remains fairly stable.
What does a healthy microbiome look like? “It’s really difficult to define,” says Weir. “But one of the things we look for is diversity, because that tends to fill all of the ecological niches in the gut, which prevents pathogens from being able to come in and take hold.”
2. The strain matters. Probiotics are bacteria (and a few yeasts) that confer some health benefit when swallowed or applied to the body.
Probiotic bacteria are identified by three names: their genus, species, and strain. The probiotic in Activia, for example, is Bifidobacterium (genus) lactis (species) DN-173 010 (strain). The genus and species are written in italic type.
To know what a probiotic bacteria can do, you need to know its strain. Yet the Food and Drug Administration doesn’t require manufacturers to disclose the strains of probiotics in their foods or supplements.
Some companies do it voluntarily, like Dannon on Activia and DanActive labels. Others—like Stonyfield Farm and Enzymatic Therapy, which sells Acidophilus Pearls supplements—refuse to.
“Manufacturers should designate the strains in their products so that con¬sumers know what they’re getting,” says Mary Ellen Sanders, of the International Scientific Association for Probiotics and Prebiotics, a group of academic and industry researchers funded by probiotics manufacturers and food companies.
“It’s pretty much a consensus among probiotic scientists that this is the responsible thing to do.”
3. You don’t need to take a probiotic every day. “One of the biggest misconceptions about probiotics is that you should be taking them daily like multivitamins,” says McFarland. “If you don’t have any reason to think there’s something wrong with your digestive system, a probiotic probably isn’t going to do much for you.”
But if someone is struggling with GI problems, says Sanders, “I tell them to try the strain-specific probiotic products that have been tested and shown to have an impact on the symptom they’re trying to deal with.”
4. Most probiotics contain what they claim. Major brands, at least, seem to have what’s supposed to be in them and at levels high enough to be useful. Last year, when Consumerlab.com tested 19 popular brands of probiotic supplements, it found that all contained the organisms that were listed on the labels. And 17 of the 19 provided at least 1 billion live organisms. If a probiotic works, that’s the minimum dose needed, most researchers agree.
Other relevant links:
• Can this Chinese herb extract help you live longer? See: Can Dietary Supplements Lengthen Your Telomeres and Help You Live Longer?
• Are bladder control supplements worth trying? See: Dietary Supplements: Do Azo Bladder Control Pills Work?
• Vitamin supplements and cancer. See: Can Vitamin Supplements Prevent Cancer?