Digestion and tolerance of lactose from yoghurt and different semi-solid fermented dairy products containing Lactobacillus acidophilus and bifidobacteria in lactose maldigesters--is bacterial lactase important?

Objective: To compare the digestibility and tolerance of lactose from three semi-solid fermented dairy products with the same amount of lactose but different lactase contents and bacterial cultures in lactase deficient adults.

Design: Measurement of breath hydrogen (H2) concentration and of clinical symptoms after consumption of the test meals.

Setting: Metabolic ward for healthy volunteers, INSERM U290, Hôpital St. Lazare, Paris.

Subjects: Fifteen lactase-deficient healthy adult volunteers (20-45 y) started the study. One subject became a non-H2-producer during the study; therefore the results of 14 subjects are presented.

Intervention: Each subject consumed, on four different days and in random order, after a 12 h fast, three semisolid test meals containing 18 g of lactose, and a 10 g dose of lactulose which allowed calculation of lactose malabsorption. The three meals were: traditional yoghurt, fermented milk (Ofilus) that contained Lactobacillus acidophilus and Bifidobacterium sp., and a similar product 'Bulgofilus' enriched with Lactobacillus bulgaricus to increase the lactase content.

Results: Compared with lactulose, the sum of symptoms was significantly lower for Bulgofilus (P = 0.05), and bloating was less severe for Ofilus (P = 0.06). Between the fermented milks, there were no differences. The area under the breath H2 curve was significantly lower for each fermented milk when compared to lactulose (P < 0.0001). The degree of maldigestion of lactose did not differ significantly between the products; it was 21 +/- 3% (range 6-52) for Ofilus, 21 +/- 3% (range 6-44) for Bulgofilus, and 18 +/- 3% (range 3-43) for yoghurt.

Conclusion: Despite the differences in the lactase and bacterial content, lactose was as well digested and tolerated from the three different semi-sold fermented dairy products. This could be due to a slow gastric emptying of the semi-solid milk.