Kefir and lactose digestion - Positive Effects of Foods

Nutrition Research Newsletter, June, 2003

Lactose maldigestion is the inability to completely digest lactose, the major carbohydrate in virtually all mammalian milks. Lactose maldigestion affects approximately 75% of the world's adult population and occurs most often as the result of a decrease in intestinal lactose activity after the age of 3 to 5 years. Lactose intolerance, on the other hand, describes the presence of gastrointestinal symptoms such as abdominal pain, flatulence, bloating, nausea, or diarrhea resulting from lactose maldigestion. The use of fermented dairy foods, such as yogurt, has been used as a strategy for overcoming lactose intolerance.

Another fermented dairy food for which claims of improved lactose digestion have been made is kefir. Since several of the microorganisms in the kefir starter culture are not typically found in yogurt, it is unknown if kefir can improve lactose digestion in a manner similar to yogurt. Therefore, a current study tried to determine whether plain and flavored kefir improves lactose digestion and tolerance in adults with lactose maldigestion and compare lactose digestion from plain and flavored kefir with yogurt, a food, which has a well-documented history of improving lactose digestion.

Fifteen healthy men and women with lactose maldigestion were included in this study. Five treatments were administered one time per subject, which was then followed by an 8-hour breath hydrogen and symptom test. All treatments were administered following an overnight fast. The five treatments consisted of 2% reduced-fat cow's milk, Lifeway plain kefir, Lifeway raspberry-flavored kefir, Dannon low-fat plain yogurt, and Dannon low-fat raspberry-flavored yogurt. The amount of lactose in each product was determined using a commercial lactose/D-galactose test kit and the portions of each product were standardized to provide 20 g of lactose. Subjects self-rated their perceived levels of severity for symptoms of flatulence, diarrhea, abdominal pain, and headache (a distracter symptom) at each hourly breath sample.

Breath hydrogen area under the curve (AUC) was low and not significantly different among the plain yogurt, plain kefir, and flavored yogurt treatments. Milk significantly increased breath hydrogen AUC compared with the plain yogurt, plain kefir, and the flavored yogurt. The flavored kefir had an intermediate response. Flatulence is the most commonly reported symptom in most lactose intolerance studies and milk significantly increased the perceived severity of flatus relative to all four treatments. The yogurts and kefirs all similarly reduced the perceived severity of flatulence by 54% to 71% relative to milk. Abdominal pain and diarrhea symptoms were negligible among the five treatments.

The results showed that plain kefir improved lactose digestion just as well as plain yogurt. Part of the explanation for this could be the high level of a-galactosidase activity in the kefir, which was approximately 60% higher than the plain yogurt. The findings also suggest that a brand of kefir that is commonly available in the United States can serve as an alternative to yogurt for improving lactose digestion. The greater breath hydrogen response to the flavored kefir was likely due to the additional sweeteners or fruit, rather than impaired lactose digestion and did not affect the clinical tolerance of the product. However, further studies are needed to elicit the mechanism of this improved lactose digestion and to determine whether brands of kefir containing different starter culture microorganisms have a similar impact on lactose digestion.

Steven R. Hertzler and Shannon M. Clancy. Kefir Improves Lactose Digestion and Tolerance in Adults with Lactose Maldigestion, JADA (103[5]: 582-587, May 2005). Address correspondence to: Steven R. Hertzler, PhD, RD, Assistant Professor, 516 D Atwell Hall, 1583 Perry St, Columbus, OH 43210-1234. E-mail: Hertzler.4@osu.edu