Most nutritionists and physicians assume that lactose intolerance means the person is deficient in the body’s production of lactase—an enzyme that breaks down milk sugar. New research, however, is indicating that probiotics are as important if not more important for the body’s ability to digest milk and break down lactose.

For this very reason, both mother’s breast milk and raw cow’s milk contain important probiotics that not only furnish lactase: Probiotics also directly digest lactose as part of their own eating regimen. Let’s look at the evidence from the research:

Scientists from the University of Buenos Aires (Gaón et al. 1995) studied 30 human subjects to see if lactose intolerance could be reduced with probiotics. Milks containing Lactobacillus casei and Lactobacillus acidophilus or no probiotics were given to the subjects. The subjects drinking the probiotic milk were significantly less likely to have bloating, diarrhea and other symptoms of lactose intolerance than the control group.

Scientists from the Chinese Center for Disease Control and Prevention in Beijing (He et al. 2004) gave live probiotic yogurt, heat-treated yogurt or acidified gelled milk (each containing 20 grams of lactose) to 45 lactose-intolerant men. Lactose digestion improved significantly among the live yogurt group compared to the other groups. The researchers concluded that, “The live flora in dairy product could improve lactose digestion in male adult lactose malabsorbers.”

Researchers from the University Medical Center Groningen in The Netherlands (He et al. 2008) gave Bifidobacterium longum and a yogurt enriched with Bifidobacterium animalis to 11 lactose-intolerant humans. Bifidobacterium levels increased during and after supplementation. B. animalis and B. longum were not detected before supplementation, but both strains were present in feces during supplementation. They disappeared after supplementation ended. Lactose-intolerance symptoms decreased during supplementation, but resumed following supplementation. The researchers noted that, “supplementation modifies the amount and metabolic activities of the colonic microbiota and alleviates symptoms in lactose-intolerant subjects.”

Scientists from the Department of Food Science and Human Nutrition at University of Missouri (Mustapha et al. 1997) determined that milk containing L. acidophilus was effective in improving lactose digestion and tolerance.

Beta-galactosidase from the yeast Kluyveromyces lactis eaten at mealtime with milk and cereal (cornflakes) and an unrefined cereal (bran) reduced lactose intolerance in a Guatamalan study (Solomons et al. 1985) of lactose intolerant patients. Exogenous betagalactosidases produced by the probiotic yeast eliminate lactose malabsorption in those deficient in lactase.

Scientists from Alabama’s A&M University (Onwulata et al. 1989) gave plain yogurt, sweet acidophilus milk, hydrolyzed-lactose milk, or a lactase tablet and whole milk to ten lactose-intolerant humans. They found that the lactase produced by the probiotics in yogurt was “superior to exogenous commercial lactase in alleviating lactose maldigestion.”

Scientists from University of Minnesota’s Department of Food Science and Nutrition (Jiang et al. 1996) gave 15 lactose intolerant patients milk with lactose control milk, or Bifidobacterium longum cultured in either lactose or both lactose and glucose. Consumption of milk with lactose-grown B. longum resulted in significantly less hydrogen production and flatulence among the patients than the other milks. The researchers concluded that, “milks containing B. longum might reduce breath hydrogen response and symptoms from lactose malabsorption when the culture is grown in a medium containing only lactose to induce a higher beta-galactosidase level and increase rate of lactose uptake.”

References are listed in Probiotics – Protection Against Infection: Using Nature’s Tiny Warriors to Stem Infection and Fight Disease.