TABLE 1.

Intervention studies investigating changes in intestinal lactase activity in humans after a lactose feeding period or a period of lactose withdrawal¹

Study population	n	Age	Intervention	Result	Reference
Lactose-malabsorbers	7	Adults	150 g lactose/d for 45 d	No change in intestinal lactase activity	(34)
Lactose-absorbers	4	Adults	150 g lactose/d for 45 d	No change in intestinal lactase activity	(34)
Lactose-absorbers	2	Adults	Abstinence from milk and milk products for 5 mo	Lactose absorption ratio decreased in both subjects	(34)
Healthy Caucasian lactose-absorbers	2	Adults	50 g of lactose 3 times/d for 10 d	No change in intestinal lactase activity	(36)
Healthy Caucasian lactase-deficient subjects	1	Adult	Diet with 30% of calories from lactose for 14 d	No change in intestinal lactase activity	(37)
Healthy Caucasian lactose-absorbers	6	—	Lactose-free diet for 42 d	Varying results in intestinal lactase activity, no change in LTT	(44)
Healthy Thai marines	50	22–30 y	25 g of lactose 2 times/d for 22–38 d	No change in intestinal lactase activity	(35)
Lactose-intolerant Nigerian medical students	6	Adults	Gradual weekly increase of lactose intake from 5 to 100 g/d for 6 mo	No improvement in LTT	(42)
Japanese nursing students	14	18–20 y	360–540 mL milk/d for 52 d	No improvement in LTT	(38)
Healthy Indians	6	Adults	30 g of lactose for 4 wk	No change in intestinal lactase activity	(39)
Lactase-deficient subjects	10	21–65 y	0.7–1.4 L milk/d for 6–14 mo	No change in intestinal lactase activity	(40)
Lactose-malabsorbing children from a Singaporean girls’ home	13	5–10 y	25 g lactose/d for 1 y	All but 1 child remained lactose-malabsorbers (per LTT)	(43)
Lactose-absorbing children from a Singaporean girls’ home	8	3–7 y	25 g lactose/d for 1 y	Only 3 children (all aged <5 y) remained lactose-absorbers (per LTT)	(43)
Healthy lactose-malabsorbing Cameroonians	16	18–26 y	18 g lactose/d for 7 d	No change in intestinal lactase activity	(41)

¹LTT, lactose tolerance test.