Yogurt is traditionally consumed throughout the world among populations
who are seemingly unable to digest lactose. This review provides
a historical overview of the studies that show lactose digestion
and tolerance from yogurt by lactose-intolerant people. The lactose
in yogurt is digested more efficiently than other dairy sources of lactose
because the bacteria inherent in yogurt assist with its digestion.
The bacterial lactase survives the acidic conditions of the stomach,
apparently being physically protected within the bacterial cells and
facilitated by the buffering capacity of yogurt. The increasing pH as
the yogurt enters the small intestine and a slower gastrointestinal transit
time allow the bacterial lactase to be active, digesting lactose from yogurt
sufficiently to prevent symptoms in lactose-intolerant people.
There is little difference in the lactase capability of different commercial
yogurts, because they apparently contain Lactobacillus
bulgaricus and Streptococcus thermophilus in sufficient quantities
(108 bacteria/mL). However, Lactobacillus acidophilus appears to
require cell membrane disruption to physically release the lactase.
Compared with unflavored yogurts, flavored yogurts appear to exhibit
somewhat reduced lactase activity but are still well tolerated.
Am J Clin Nutr 2014;99(suppl):1251S–5S.