Do probiotics really do anything?

This woman may be getting a healthy dose of bacteria AND catching up on e-mail. See more staying healthy pictures.
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The United States is known for its multitasking at mealtime. While other cultures enjoy long, leisurely meals, Americans head to the lunch meeting, in which a sandwich is accompanied by statistics. At dinner, we find ourselves juggling cell phones, children and the evening news while we eat. It's no wonder then that Americans find themselves interested in improving their health while they eat their favorite foods. Maybe we buy the juice claiming to have extra vitamins or the snack bar boasting of its full-day supply of fiber. That's some mighty multitasking -- eat some food you were going to eat anyway and get a health benefit. And market research has found that people would rather eat food with something healthy than take another pill, which is why functional foods, or food with an added health benefit, have become big business.

Take Activia, a yogurt made by Dannon. In the first year that Activia was on the market, it racked up more than $100 million in sales in the United States [source: Martin]. Activia is probably the most well-known example of a product fortified with probiotics, and Activia's success portends a lot of interest in loading probiotics into other functional foods. Europe and Japan have been hip to probiotics for awhile now. But what are probiotics, and why should we care about a yogurt packed with them?


While a lot of American shoppers may have been attracted to Activia by celebrity spokeswoman Jamie Lee Curtis, they actually have the people of Bulgaria to thank for their probiotic yogurt. At the beginning of the 20th century, Russian scientist Elie Metchnikoff determined that a diet of fermented milk products resulted in a long, healthy life for Bulgarian peasants [source: Sanders]. Probiotics, meaning "for life" in Greek, became the term for the bacteria that was found in those fermented products. The bacteria have a very technical definition provided by the World Health Organization; they are "live microorganisms which, when administered in adequate amounts, confer a health benefit on the host" [source: Brody].

But what this means in practice can frankly be as confusing as Bulgarian to an English speaker. In essence, proponents of a probiotic diet say that probiotics are "good" bacteria that are needed in the gut, and that their presence could result in a whole host of health benefits, everything from reducing lactose intolerance to curing yeast infections. Critics of the probiotic movement, however, say that the evidence just isn't there for these claims, and that what's more, even if the science did demonstrate the benefits, it would be impossible to fill the right amount of these bacteria into a food product. So who's right? Should you add probiotic products to your shopping list, or do they do nothing at all?


Probiotic Bacteria

If it seems like you're waiting a lifetime for a bowel movement, then you might want to ask your doctor about probiotics.
If it seems like you're waiting a lifetime for a bowel movement, then you might want to ask your doctor about probiotics.
Mike Kemp/Rubberball Productions/Getty Images

While probiotics have long been popular in Europe and Japan, these friendly bacteria are just now making it to North America in food products and dietary supplements. But it's not just a matter of swallowing random bacteria. The two main types of bacteria considered to be probiotics include strains from the Lactobacillus and Bifidobacterium genera (other genera, such as Escherichia, Enterococcus and Saccharomyces have also been designated probiotics, but to a lesser and more questionable extent). Lactobacillus and Bifidobacterium are made up of different strains, each of which has a different health function. To truly understand the potential benefit to your body, you have to research the difference between Lactobacillus acidophilus and Lactobacillus rhamnosus.

In general, though, probiotics are espoused for a variety of ills, everything from constipation to cancer treatment. Scientists believe that probiotics work by repopulating the gut with good bacteria, which can be eliminated along with bad bacteria during a course of antibiotics. Additionally, probiotics are believed to have the power to fight off pathogens and toxins, as well as strengthen the gut fortresses that will eventually have to do battle with the same.


How does this hypothesis of how probiotics work translate into a health benefit? In some cases, the evidence is a bit shaky. Right now, the clearest benefit of probiotics, backed up by scientific study, comes in the field of gastrointestinal conditions, such as antibiotic-associated diarrhea, acute infectious diarrhea (such as traveler's diarrhea) and irritable bowel syndrome. In one study, probiotics reduced the risk of developing diarrhea associated with antibiotics by 52 percent, and they have been shown to cut the risk and duration of infectious diarrhea as well [source: Kligher, Cohrssen]. Probiotics are successful in treating diarrhea caused by rotavirus in children as well.

As for irritable bowel syndrome, probiotics seem to have the neat effect of both relieving you when it won't come out (constipation) as well as when too much is coming out (diarrhea). In the case of Activia, Dannon's studies show that Activia can speed up the amount of time it takes for waste to exit the system by about 40 percent, if a person with irregular bowel movements were to eat one container a day [source: Warner].

­As for the rest of the claims, the evidence is not quite there. While some research has demonstrated effectiveness, more studies are needed to back up claims regarding the effect of probiotics on childhood allergies; urogenital infections including urinary tract infections, bacterial vaginosis and yeast vaginitis; upper respiratory infections; breast and colon cancer; and lactose intolerance.­

If the results aren't completely in, then how can manufacturers already have probiotic products on the market for these conditions? Find out about how the package doesn't always match the product on the next page.

Probiotic Food Packaging

Seeking guidance on the label? When it comes to probiotics, you may not find what you're looking for.
Seeking guidance on the label? When it comes to probiotics, you may not find what you're looking for.
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To actually create some effect in your body, probiotics need first-class travel on the journey that is your digestive system. They have to be encased in something strong enough to survive the acid-filled stomach, but not so strong that they don't dissolve in the intestines, where they do their best work. The bacteria can be damaged by air and moisture, so extreme care has to be taken in creating food products with probiotics. These items may not have a particularly long shelf life.

Further complicating the problem is the fact that in some instances, scientists aren't sure of the exact dosage of bacteria that will confer health benefits, and because we're dealing with live bacteria here, it's hard to know how many you add to a product end up remaining viable in each serving. Additionally, the only way to determine how many probiotics actually made it through the gastrointestinal tract is to examine the fecal matter of those who consumed the probiotics, a research study that certainly doesn't sound appealing to this writer. And even that number would be circumspect, because while the feces would reveal how many bacteria made it down the tract, it wouldn't reveal how many probiotics actually did the job they were supposed to do in the gut.


N­ot that you'll find this information on the package; critics of probiotics food worry that labels don't always indicate which bacteria are present or how much of the ingredient is there. Some manufacturers may just slap the probiotic label on an item that doesn't have enough bacteria to make any sort of difference. For now, consumers won't get any help from the FDA, either. While the FDA has strict rules about marketing items that claim to cure disease, they don't have restrictions for items that talk in fairly general terms about bodily health, which is why you'll see Activia marketing its asset as an ability to regulate the digestive system, as opposed to being a cure for constipation [source: Warner].

Such vague claims may lead a consumer to believe that probiotics should be added to a regular, everyday diet. But are there health benefits for those that are already healthy? There are few studies on how probiotics affect the immune system of a healthy person [source: Senok et al.]. The effects of probiotics are temporary, though, which means you have to keep consuming them, and if you're going to add a daily step to your routine, it may be more advantageous to consider measures with proven benefits, such as diet and exercise. Already nutritionists worry that consumers will add these products to their diet, rather than substituting them for something else, potentially leading to an excess of calories.

But what if you just love the taste of Activia, or you're already devoted to your probiotic supplement? Though there may be no definitive proof of the health benefits yet, there's also little evidence that you're doing harm to your body, either. Flatulence and abdominal discomfort are the only real side effects that have been reported [source: Kligher, Cohrssen]. However, one important exception exists: In a study group of nearly 300 patients with pancreatitis, the patients who received probiotics rather than a placebo were more likely to require intensive care and surgical intervention, even though the severity of illness was roughly the same before the study [source: Bakalar]. In the group taking probiotics, 24 people died, more than twice the number of deaths in the placebo group [source: Bakalar].

So do probiotics really do anything? Right now, the answer seems to be a big, fat maybe. But with consumers interested in natural health and manufacturers eager to cash in on the functional food fad, we can hope for more studies that will shed a light on the subject. For health-related subjects we already know a fair bit about, head on over to the next page and see the links there.

Related HowStuffWorks Articles

More Great Links


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  • Bakalar, Nicholas. "Diet Supplement Seen as Risky for Some Users." New York Times. Feb. 19, 2008. (Nov. 18, 2008)
  • Bee, Peta. "Probiotics, not so friendly after all?" The Times. Nov. 10, 2008. (Nov. 18, 2008)
  • Brody, Jane E. "Putting Good Bacteria to Work." New York Times. Sept. 14, 2004. (Nov. 18, 2008)
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  • Kligler, Benjamin and Andreas Cohrssen. "Probiotics." American Family Physician. Nov. 1, 2008.
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