Probiotics are a big and rapidly growing business, with annual global sales of products expected to rise to $42 billion by 2016. The term probiotic refers to dietary supplements (tablets, capsules, powders, lozenges and gums) and foods (such as yogurt and other fermented products) that contain “beneficial” or “friendly” bacteria, as well as to the organisms themselves. They are promoted to improve digestion, strengthen immunity, help in weight loss and even protect against periodontal disease, among other proposed benefits, as well as for general health. Will the friendly bacteria in these supplements and foods keep you healthy?
Proponents claim that probiotics (meaning “for life,” as opposed to antibiotics) confer health benefits primarily by rebalancing the normal microflora in the large intestine (colon). There are many general types of bacteria used as probiotics (two common ones are Lactobacillus and Bifidobacterium), and many different species as well as strains within species. They have different physiological effects—and thus possibly different health benefits (as well as possible risks). Some yeasts, such as Saccharmyces, can also act as probiotics. Probiotic products may contain a single strain or many strains, and the number of organisms in a daily dose can range from 1 billion to more than 250 billion. Many manufacturers boast that their products contain unique probiotics and/or combinations of strains that make them even better for you—and often charge a premium price. It’s a mad, mad probiotic world.
A probiotic primer
The large intestine is home to hundreds of trillions of bacteria. Fortunately, most are neutral or even beneficial, performing many vital body functions. For example, they help keep “bad” bacteria at bay, play a role in immunity, help us digest food and absorb nutrients and may even have anticancer effects. But will consuming them as probiotics in foods or capsules make a notable difference to your health—especially if you are already healthy? That’s what manufacturers want you to believe. Here’s a look at the evidence.
Digestive problems. The best support for probiotics is for reducing diarrhea, especially infectious diarrhea and diarrhea associated with antibiotic use. Two reviews from 2012, one in the Journal of the American Medical Association (JAMA) and one in the Annals of Internal Medicine—which together included more than 80 studies and 14,000 people—found that probiotic therapy reduced the risk of antibiotic-associated diarrhea (including that caused by the bacterium Clostridium difficile, which can be life-threatening) by 42 and 66 percent, respectively.
Some studies suggest that certain probiotic strains also help in mild to moderate ulcerative colitis (a type of inflammatory bowel disease) and possibly irritable bowel syndrome. And certain strains have been shown to improve stool consistency and increase frequency of bowel movements in people with constipation. But larger well-designed studies are needed to confirm such benefits. The common “structure/function” claim that probiotics “support good digestive health” (or some variation)—though allowed by the Food and Drug Administration (FDA)—is really a meaningless creation of the advertising world.
Immunity and infections. There’s a close connection between the bacteria in your intestines and the immune system—and probiotics have been linked to enhanced immune responses (such as to flu vaccines). But studies have been inconsistent as to whether taking probiotics will actually curb colds and other upper respiratory infections. A 2011 Cochrane review concluded that they may be beneficial for preventing acute respiratory infections, though there were limitations in the studies and no data for older people. A large, well-designed study published in the American Journal of Clinical Nutrition in 2012 found that drinking a fermented yogurt beverage containing a certain strain of L. casei every day for six months did not reduce respiratory symptoms in elderly people.
Weight loss. There may also be a link between intestinal bacteria and obesity, some research suggests. But there’s little published clinical work showing that probiotics will help promote weight loss. A study in the European Journal of Clinical Nutrition in 2011 found that people who drank fermented milk with a particular strain of Lactobacillus gasseri for 12 weeks had a reduction in abdominal fat and body weight, compared to those consuming a control drink. Another study, published in the Journal of Functional Foods in November 2012, found that people who consumed yogurt containing two “novel” strains of probiotics experienced small losses in body fat, but no changes in body weight.
Oral health. In addition to the microflora that reside in the large intestine, bacteria populate the mouth as well. An increasing number of probiotic lozenges and gums are thus being promoted for oral health—for example, to reduce periodontal disease, throat infections, and bad breath. There’s preliminary evidence that certain strains may have some benefits, but commercial products may not have the same strains and formulations as those tested in published studies. Don’t expect these products to replace brushing and flossing.
Other uses. Many other claims are made for probiotics—that they lower blood pressure and cholesterol, alleviate skin conditions like eczema, treat ulcers and urinary tract infections, improve vaginal health, prevent colon cancer, ease anxiety and depression and ward off traveler’s diarrhea. But the evidence so far is preliminary, at best. Don’t count on eating yogurt or douching with it to ward off or cure vaginal yeast infections.
Even if probiotics are beneficial for certain medical conditions, you’d have to take the right strain and right dose, which even scientists don’t know for certain. And not everyone will even respond the same way to a given probiotic—much depends on the intestinal bacteria you have to begin with, your immune status and other factors.
In addition, there’s no guarantee that products contain the numbers of organisms claimed on labels—or that the organisms are even alive and survive digestion. And if they do survive, it’s not certain they will colonize the intestines in sufficient numbers to have most of the proposed benefits. Some manufacturers claim to use processes that ensure that the bacteria stay alive and have therapeutic effects, but very few products undergo independent verification. Recent testing by ConsumerLab.com of 29 probiotic products found that while all contained at least one billion organisms per daily dose (“an amount that may provide some benefit”), a few had far lower amounts than claimed on the label.
Probiotics in Yogurt
Whether yogurts and other fermented dairy products (such as kefir) provide probiotic health benefits is debatable, but they are excellent foods, high in protein and calcium. The voluntary “Live & Active Culture” seal from the National Yogurt Association is the best assurance that a certain number of bacteria were present at
Probiotics are considered safe overall for healthy people; short-term side effects may include mild gas and bloating. But keep in mind that if they do have physiological effects, these may not always be good effects. There’s concern about the safety of certain strains in people with underlying health problems—for example, that they may overstimulate the immune system or cause blood infections. If you are immune-compromised, have certain bowel problems or are seriously ill in other ways, avoid probiotics unless your doctor has okayed their use. Probiotics should be used cautiously by pregnant women, infants and young children and never given to premature infants.
Bottom line: Probiotics are a promising field of research and may one day be used to treat or help prevent many disorders. But there’s not enough solid evidence to recommend their widespread use. Larger, longer studies are needed to test specific strains against specific conditions and to determine the proper doses and regimens. The FDA has not approved any specific health claims for probiotics and has called claims made by some manufacturers, including yogurt companies, misleading. Going one step further, the European Union recently deemed that any reference to the term “probiotics” on packaging is unauthorized and subject to legal action.
Probiotics and Antibiotics
If you are taking antibiotics, there’s no harm in eating yogurt to try to prevent diarrhea. But check with your health care provider or pharmacist first, since the calcium in dairy foods can interfere with the absorption of certain antibiotics. If you want to try a probiotic supplement instead, ask if