Drinking fermented milk appeared to eliminate or drastically reduce symptoms related to lactose intolerance in people with the allergy, report researchers at Columbus University, Ohio.
The scientists believe that microbes in the fermented milk kefir possess the enzyme that is necessary to digest lactose.
"Many health claims exist for kefir, including the enhancement of the immune system and improved digestive health, particularly with regard to lactose digestion," said Steven Hertzler, a study co-author and an assistant professor of medical dietetics at Ohio State University.
The small study showed that when participants drank the milk alternative they had few symptoms of the condition.
Kefir is made by adding clusters of starchy carbohydrate - kefir grains - that contain healthy bacteria and are left to ferment in milk. The grains are filtered out while the live cultures remain.
In the study, published in the May issue of the Journal of the American Dietetic Association, 15 adults consumed five separate test foods: 2 per cent milk; plain kefir; raspberry-flavoured kefir; plain yoghurt; and raspberry-flavoured yoghurt. Each food was eaten after a 12-hour fast and followed up by a series of breath hydrogen tests every hour for eight hours. Participants were asked to record any symptoms of lactose intolerance for eight hours after eating each food.
Previous research has suggested that eating fermented dairy products, such as yoghurt, improves lactose digestion. Participants in the current study reported having little or no symptoms associated with lactose intolerance after eating both types of yoghurt and kefir, said the researchers. Flatulence, the biggest complaint among lactose-intolerant people, was the most-reported symptom but drinking kefir reduced flatulence frequency by more than half, compared to milk, they said.
Breath hydrogen levels, indicative of excessive gas in the digestive tract, were also significantly lower after consuming the plain and flavoured kefir than after drinking milk.
While it is known that lactose intolerant people can tolerate yoghurt - it contains healthy bacteria that break down lactose - Hertzler suggests that kefir might be a better option for some lactose intolerant people. Like yoghurt, kefir is a good source of calcium, potassium and protein, but it also contains a wider array of microorganisms than yoghurt does, he said.
"Both kefir and yoghurt improve lactose digestion simply because some of the bacterial cells give up their lives in the intestinal tract, release their enzymes and digest the lactose," Hertzler said. "It's a one-shot deal. However, kefir has additional microorganisms that may be able to colonise the intestines and benefit health further by protecting the intestine against disease-causing bacteria."The food intolerance and allergies market is growing rapidly as consumers focus increasingly on diet as a factor in their health. In the UK the sector has grown 165 per cent since 2000, according to market analysts Mintel, and is set to more than double in value by 2007 reaching £138 million (€202m).
This study was funded by US-based kefir manufacturer Lifeway Foods.