Four lactobacilli-containing milks and a control were fed to 12 lactose maldigesters in a random, blinded protocol. Milks contained 108 cfu/ml of either Lactobacillus acidophilus LA-1 or Lactobacillus gasseri ADH prepared with commercially obtained frozen or freshly grown cultures.Breath hydrogen (H2) production and symptoms were monitored to evaluate lactose digesion and tolerance. Total H2 production was modestly reduced following consumption of the lactobacilli milks, but the differences failed to reach significance (P=0.07 for LA-1 and P=0.36 for ADH). All subjects reported less severe symptoms, primarily flatulence (P=0.06), following consumption of lactobcilli milk. Frozen cultures of LA-1 exhibited a 70-fold higher β-galactosidase (β-gal) activity (per cfu) than frozen ADH. Cell counts were 10 fold higher with LA-1 than with ADH, when grown in vitro in modified MRS media. β-gal activities of lactobacilli grown in MRS with only lactose were 4-to 11-fold above enzyme activities in MRS with hoth glucose and lactoe. The results demonstrate that different levels of β-gal in Lactobacilli-containing milks may produce similar improvements in lactose digestion and tolerance. It is likely that β-gal activity is a necessary, but not sufficient attribute for optimizing lactobacilli enhancement of in vivo lactose digestion. 本研究以十二患有乳糖不耐症者進行人體試驗，十二位試驗者先後喝下四組含有乳酸菌的試驗組牛乳及一對照組牛乳。試驗組牛乳中含有108cfu/ml的乳酸桿菌Lactobacillus acidophilus LA-1或Loctobacillus gasseri ADH (為冷凍濃縮菌種或實驗室培養菌種)。由氫氣濃度結果顯示，含乳酸菌的牛乳稍稍改善(未達顯著)人體對乳糖的利用( P=0.07 for L. acidophilus LA-1,P=0.36 for L. gasseri ADH ),而且含乳酸菌的牛乳也減輕了試驗者的不適症狀，尤其是腹脹情形( P=0.06)。另外在不同的培養條件下，發現冷凍濃縮的L. acidophilus LA-1的β-半乳糖甘酶活性約為L. gaseri ADH的70倍。當以改變糖含量的MRS培養時，活菌的數目LA-1約誇ADH的10倍。而當MRS只含有乳糖時，所培養出來的乳酸菌其β-半乳糖甘酶活性較含葡萄糖與乳糖培養者高4至11倍。此外，由本實驗結果可知，雖然不同的乳酸菌具有差異極大的β-半乳糖甘酶活性，但可造成類似的乳糖利用吹進效果，因此可推斷β-半乳糖甘酶為乳酸菌必要但非唯一的改善乳糖利用的特性。
