To Your Health
January, 2009 (Vol. 03, Issue 01)
Certain isolated prebiotics called "fructooligosaccharides" (or "fructans" for short) encourage the growth of specific types of beneficial bacteria. Inulin, commonly added to foods, is one such prebiotic fiber, usually extracted from the root of the chicory plant. Fructans such as inulin are the major source of prebiotics in the U.S. food supply.
Consumers are at a disadvantage when it comes to consuming prebiotic supplements beyond diet alone, because products vary considerably in the amount and quality of health information that are provided on labels. Some of this has to do with government regulation of the industry. For example, some prebiotic products may contain quite high amounts of fermentable fiber, yet do not provide any health claim information on the labeling because of government rules. This can be confusing, and that is when consulting your doctor and/or other nutrition professional, such as a dietician or a clinical nutritionist, may be prudent. Typically, the amount of prebiotic associated with health benefits is between 3 and 8 grams per serving. It is difficult to get this much prebiotic from a pill (although such products exist), so many prebiotic products are presented as cereals, snack bars or powdered shake mixes.
Probiotics: Living Microorganisms
Probiotics are indeed living microorganisms (typically bacteria, but also some yeasts) that have health benefits in humans when consumed in adequate amounts. A probiotic is not the same thing as a "live culture," which is a microorganism added to food primarily as a fermenting agent. While some live cultures are probiotics (yogurt cultures, for example), many organisms are never used as food additives, such as certain species of E. coli.
A common misconception about probiotics is that eating them helps to establish colonies of these same microbes in the body. That is a myth not supported by science. After consuming probiotics, there is a temporary increase in concentrations of the specific ingested organisms in the gut, but levels typically drop back down after the person stops ingesting them. These probiotics simply create more favorable conditions so that colonies of healthy bacteria already living in the gut can thrive and compete against pathogenic bacteria that may cause illness. Probiotics do this in part by lowering the pH of the gut and secreting factors that support growth of beneficial bacteria while inhibiting pathogens.
In generally healthy people, probiotics can support the health of gastrointestinal tract and the immune system, as well as help prevent certain health conditions, including diarrhea and colds. Probiotics support the immune system by enhancing the body's immune response to pathogens and decreasing inflammation.
As with prebiotics, there are plenty of common foods that contain probiotics. Yogurt, some cheeses and fermented milk products, such as kefir, are examples. The most common commercial probiotics found in foods are species of Lactobacillus and Bifidobacteria, and occasionally the yeast Saccharomyces cerevisiae. Other types of bacteria may be found in probiotic supplements, but rarely in foods.
Healthy people may be tempted (or persuaded by manufacturers) to try probiotic supplements known to enhance immune function and reduce the risk of common illnesses such as colds, flu and even diarrhea. But they may be better off trying to increase their consumption of common probiotic foods instead. While probiotic-rich diets have not been specifically tested for their health benefits, there is evidence that including a variety of probiotic foods in the diet is beneficial.