Depending on the brand, both kefir and yogurt can contain healthful bacteria, called probiotics. Thousands of studies, spanning decades of research consistently show that encouraging the growth of healthy bacteria in the digestive tract could lower the risk for a wide variety of diseases, ranging from diarrhea to cancer. Beyond just supplying vital nutrients, some supplements and fermented foods including yogurt and kefir, contain live microbial food constituents, called probiotics, that when ingested exert health benefits. A strain of bacteria is only considered a probiotic if it survives the acidic environment of the stomach to exert healthful benefits in the intestine. Some of the strains found to be most beneficial include Lactobacillus acidophilus, Bifidobacterium, and L. rhamnosus.
The microflora in the gastrointestinal tract contains both probiotic and pathogenic bacteria. Encouraging the growth of probiotic bacteria is important in maintaining an effective intestinal barrier, enhancing nutrient absorption, and blocking toxins and pathogens. Probiotics reduce the adhesion of pathogens to the intestinal mucus. They help ferment fibers, producing fatty acids that support a healthy intestinal barrier, inhibit the growth of harmful bacteria, and aid with stool regularity. As a result, a main function of probiotics is to lower the risk for traveler’s diarrhea and diarrhea caused by antibiotics, rotavirus, and impaired bowel function. Probiotics also aid specialized lymphoid follicles of the gut mucosa, thus encouraging optimal immune function. They shorten or reduce the risk for infections (especially intestinal viruses and fungus infections), curb the severity of lactose intolerance symptoms, and reduce the risk for certain allergies. Probiotics also reduce the severity of microbe-induced gut inflammation, acute gastroenteritis, inflammatory bowel disease, irritable bowel syndrome, Helicobacter pylori infection, and colorectal cancer. Recent studies suggest that probiotics also might help with weight loss. Benefits are noted in all age groups, from infants to the elderly. The main difference between kefir and yogurt is that kefir appears to have anywhere from 10 to 20 times the amount of probiotics per serving, and also contains healthful yeasts. Always check the label and choose products that give you at least the short list for which probiotics are present.
Both kefir and yogurt also are great sources of calcium and protein. Some products also are fortified with vitamin D. Choose low-fat or fat-free options, since the full-fat varieties can be very high in calories and fat (up to 8 grams of artery-clogging saturated fat per serving). Also, check the label for added sugars, since many varieties and brands of both flavored kefir and yogurt have the sugar equivalent of a candy bar.