July 21, 2008

Happy Entrails — A Close Look at Digestive Health Claims
By Sharon Palmer, RD
For The Record
Vol. 20 No. 15 P. 24

Cultures are chic, but the science on foods touting digestive defense abilities is still fermenting.

Functional foods marketed to help consumers achieve a healthy gut are en vogue. A visit to the supermarket or natural foods store yields glimpses of many products infused with healthy bacteria, including yogurts that “help to naturally regulate your slow intestinal transit,” cereals that “help care for your digestive system,” and supplements that “help build and maintain a natural defense against episodic constipation, diarrhea, urgency, gas, and bloating.”

Consumers are eating up the digestive health statements on food products. According to the 2007 International Food Information Council Foundation Food & Health Survey, 76% of consumers believe foods and beverages can help improve digestive health. “People are becoming more interested and aware of foods for digestive health,” says Miguel Freitas, PhD, medical marketing director for The Dannon Company, Inc.

There are generally two groups of people on the lookout for these products: healthy people searching for products to aid in maintaining good health and those with specific health concerns.1 According to the Foundation for Digestive Health and Nutrition, more than 70 million Americans have digestive disorders that interfere with their lives, resulting in an estimated $91 billion in annual healthcare costs, lost work days, and premature deaths.

Even though people specifically seek probiotics in foods, they may not grasp the complicated science behind the products. While they may understand that fiber in whole grains, fruits, and vegetables has intestinal benefits, consumers often have trouble wrapping their minds around the concept of healthy bacteria, according to Freitas. “The perceptions about bacteria in general are still not entirely accurate. But we see in our consumer research that an increased number of consumers are aware of and understand the benefits of probiotics. Bacteria are becoming less and less associated with only bad bacteria,” he adds.

Just how compelling is the evidence behind foods marketed for digestive health benefits? “Digestive health is a developing concept. We know when our digestive system is not healthy, but we don’t have great biomarkers of digestive health. So consumers should be skeptical of claims,” says Joanne L. Slavin, PhD, RD, a professor in the department of food science and nutrition at the University of Minnesota.

In the December 2006 issue of Nutrition Action Healthletter, author David Schardt noted that many leading brands of probiotic foods and supplements lack the evidence to support their claims. And in January 2008, a lawsuit filed in Los Angeles federal court claimed that Dannon lured consumers into paying more for Activia (Dannon’s yogurt brand marketed to help regulate the digestive system) based on a false advertising campaign. The lawsuit seeks to reimburse consumers, as well as have Dannon correct its advertising campaign. Freitas reports that Dannon stands behind its claims, with scientific information published in peer-reviewed journals and available on its Web site.

The Down and Dirty on Healthy Bacteria
The notion that probiotics contribute to health dates to the 19th century, when a Russian immunologist linked Bulgarian peasants’ longevity to their intake of fermented milks containing Lactobacillus. Today, we understand that microbes are symbiotic coresidents in our bodies that appear to play a role in immune development and resistance to infection. Our bodies are home to about 100 trillion bacteria living in constant dynamic interaction with us and each other. Most microbes are harmless and have important functions in the body, such as gut barrier function, intestinal function, digestion, and immune development and function.1

In 2001, the World Health Organization/Food and Agricultural Organization of the United Nations defined probiotics as live microorganisms that confer a health benefit to the host when administered in adequate amounts. Our intake of probiotics is much lower now than it was during ancient times, which some experts believe may contribute to increasing inflammatory and allergic disorders in our society.1

The scientific literature has related probiotics to a plethora of benefits, including regulating immune function, prolonging remission in patients with pouchitis, shortening the duration of infectious diarrhea in infants, enhancing gastrointestinal tolerance to antibiotic therapy, and controlling symptoms associated with lactose intolerance.1 Emerging human evidence has linked probiotics with reducing incidence and improving symptoms of some allergic diseases, improving therapeutic outcomes for women being treated for bacterial vaginosis, improving symptoms of irritable bowel syndrome (IBS), decreasing the incidence of dental caries, reducing the severity of symptoms or incidence of respiratory infections, reducing Clostridium difficile toxin in subjects taking antibiotics, and reducing absences or illnesses in workplace or day care center settings.1

Prebiotics promote the growth of beneficial bacteria. A recent definition for prebiotics reported at the September 2007 Food and Agricultural Organization of the United Nations Technical Meeting on Prebiotics is “a selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microbiota that confers benefits upon host well-being and health.” Scientists are investigating prebiotics for antipathogenic effects, decreased fecal transit time, decreased cholesterol levels, lowered glycemic response, improved bone health, lower daily energy intake, relief of inflammatory bowel disease symptoms, and decreased colon cancer rates. Common prebiotics include inulin, fructooligosaccharides (FOS), galactooligosaccharides, soyaoligosaccharides, xylooligosaccharides, pyrodextrins, isomaltooligosaccharides, and lactulose. There is growing interest in combining prebiotics and probiotics for greater benefits. For example, research on humans has suggested that the overall effect of L. acidophilus was enhanced by a coadministration of short-chain FOS.1

Not All Probiotics Are Created Equal
There’s no denying that people are becoming enamored with probiotics for their purported health benefits, but these effects may be limited to particular strains. Many health professionals simply advise people to look for live active cultures as a source of probiotics. But Mary Ellen Sanders, PhD, a probiotic microbiology consultant and coauthor of the article “Probiotics and Prebiotics in Dietetics Practice” in the Journal of the American Dietetic Association, stresses, “Live active cultures are not the same as probiotics. Live active cultures may or may not have any probiotic effect.” Products contain different genera, species, or even strains of the same species, and not all microbes sold as probiotics have been tested for health effects; thus, not all products with probiotics have the same effects.1

The most common probiotics in U.S. products are strains of different species of Lactobacillus or Bifidobacterium, although the yeast Saccharomyces cerevisiae (boulardii) is also used. Bacterial strains of Enterococcus, Bacillus, and Escherichia are found mostly in supplements. Researchers have investigated various strains for specific benefits—from treating infant diarrhea to aiding irritable bowel symptoms.1

The appropriate dosage of probiotics depends on the strain and the specific health benefits attached to it. Few published studies show positive effects at levels below 100 million colony-forming units per day, and levels much higher than this may be required to achieve certain health effects. Lactobacillus, Bifidobacterium, Saccharomyces, and Streptococcus thermophilus are considered safe for generally health people, but immunocompromised patients or the severely ill should use caution. Supplemental forms of probiotics may include species of Bacillus, Clostridium, Enterococcus, and E. coli, which should be considered carefully before taking.1

Looking Beneath the Probiotics Label
With probiotics making an appearance in everything from bread to supplements, how can consumers know they are getting products that can provide real benefits? After all, there is no FDA-approved health claim for probiotics and no legal definition of the term probiotics. Foods and supplements containing probiotics are allowed to display structure or function claims as long as they are truthful and not misleading. But not all products claiming to be probiotic contain adequate levels of a scientifically documented strain.1

 “It’s the Wild West; some companies are doing what they want to do with probiotics in foods without clinical evidence and claims substantiation. There [are] no police coming out and saying that you need to have a certain amount of probiotics and that you need to have at least two clinical studies to back up a specific claim that is made,” says Freitas.

When a product calls itself probiotic, rarely does it provide objective proof through independent third-party analysis. Product labels and Web sites are currently the main sources of information for finding out what types of probiotic microbes products contain, what levels are in products through the end of shelf life, whether the products have shown health benefits in human studies, and whether the claims are validated.1

 “It’s not always easy to translate science into a message consumers understand. Some probiotic products don’t show data on what they are selling consumers on. Some probiotic products don’t have data supporting their label claims. Some products don’t specify the strains found in the product. It’s hard to differentiate the good from the bad. I suggest that people … buy from companies that they trust and read the labels,” says Sanders.

Are all probiotics in products alive and well, ready to work in the human body? There is concern about the viability of probiotics in products, since they are sensitive to heat, moisture, oxygen, and acid. Food makers have developed technologies such as microencapsulation, or coating, that improve probiotic survival after ingestion.1 “Probiotics are usually destroyed in cooking, microwaving, or slow freezing, such as in making ice cream,” says Freitas, who notes that it is important for clinical studies to investigate the effectiveness of the probiotic in a product rather than relying solely on previous data on a particular strain outside of that medium.

In a December 2006 product review of probiotic supplements, ConsumerLab selected 13 probiotic products sold in the United States and/or Canada and found that only eight of these contained at least 1 billion organisms per daily dose (a generally recommended minimum) and any higher amounts that they may have claimed on their labels.

Putting Probiotics Into Professional Practice
Like consumers, health professionals are waking up to the possibilities of probiotics for their patients and the public. “The medical community is starting to be more aware of foods for digestive health benefits. Our research indicates a significant increase in the recommendations for probiotics in the medical community, mainly by gastroenterologists, since last year,” says Freitas.

“It makes sense to incorporate yogurt with live active cultures as part of a healthy diet to provide complete protein and calcium but also live bacteria that have been part of the human diet for thousands of years. But for clients with specific problems such as mild IBS, diarrhea, or antibiotic side effects, it’s a stronger recommendation to suggest products with research that has documented these effects,” says Sanders.  

Unfortunately, it is difficult to provide specific recommendations for probiotics because species, applications for specific strains, dosages, forms, safety, and shelf life are not well summarized or available in a practical form. “You really do have to sort through the information on probiotics. I try to provide information from a nonindustry perspective. I include only published data that is peer reviewed and retrievable,” she says.

— Sharon Palmer, RD, is a freelance food and nutrition writer based in southern California.

Reference
1. Douglas LC, Sanders ME. Probiotics and prebiotics in dietetics practice. J Am Diet Assoc. 2008;108(3):510-521.