What exactly does probiotic mean?
Yogurt's most recent claims to fame have been as a probiotic, a product containing bacteria that are beneficial to the gut. Yogurt becomes a probiotic when the starter cultures used to ferment milk into yogurt are allowed to continue to live in the finished product. Traditionally, Lactobacillus bulgaricus and Streptococcus thermophilus have been the cultures used in yogurt making. In recent years, some manufactures have added extra cultures to yogurt during processing to enhance its probiotic properties. Cultures added most often include Lactobacillus acidophilus, L. casei, L. reuteri and Bifidobacterium bifidum (Bifidus). These bacteria are considered to be probiotics because they are able to survive through the stomach to the gastro-intestinal tract. Once in the GI tract, they serve as friendly bacteria to help maintain a healthy balance between the 200-plus kinds of bacteria that live there.
Currently, starter cultures and probiotics are being investigated for their possible role in just about everything from improved digestion and reduced risk of intestinal infection to improved immune function and reduced risk of certain cancers. As is typical, the results vary from claim to claim and study to study.
The most substantiated claim about yogurt is its beneficial effect on digestion in some individuals. People who are lactose intolerant have a hard time digesting milk products because they lack the enzyme lactase that breaks down the main carbohydrate in milk. Yogurt is a unique dairy food because the starter cultures actually produce lactase during fermentation. Thus, the milk sugar in yogurt is more easily digested, even for lactose intolerant individuals. Many people who commonly experience gas, bloating or discomfort from dairy foods are able to digest yogurt more easily, thanks to the starter cultures. This is especially true if the yogurt contains live cultures.
Claims regarding the usefulness of yogurt containing probiotics in reducing the risk of intestinal infections also seem to have some merit. Studies have shown, for example, that children suffering from chronic diarrhea recover faster when fed yogurt with probiotic cultures. Adults suffering from traveler's diarrhea also seem to benefit. Scientists attribute this to probiotics' apparent ability to create an acidic environment that inhibits harmful bacteria.
Research examining the relationship between yogurt cultures and reduced risk of cancer has been mixed. Results from animal studies suggest yogurt with active starter cultures and probiotics may enhance certain immune functions; however, studies in humans have been inconsistent. Likewise, good evidence is lacking for the association between reduced cancer risk and probiotics. As for yeast infections, there have been plenty of anecdotal stories of increased yogurt and probiotic intake appearing to diminish the incident of yeast infections, but good studies on this promising topic have not been completed.
To maximize yogurt's health benefits look for a "Live and Active Cultures" seal on the label. This seal indicates that the yogurt meets the National Yogurt Association's criteria for live and active culture yogurt. For the added benefit of probiotics, look for any of the above listed probiotics on the ingredients list. L. acidophilus is by far the most commonly added probiotic.
*excerpts taken from: By Pat Kendall, Ph.D., R.D. Food Science and Human Nutrition Specialist Colorado State University Cooperative Extension June 25, 2001