The Nutritive Value of Lactose

Abstract

The nutritive value of lactose in the rat as compared with that of glucose and sucrose was studied by noting the weight gain after the sugars were added in equivalent amounts to a sub-maintenance diet. The weight gain after lactose was added to the diet was at first slightly greater than that after glucose or sucrose addition, but after the fifth to the ninth day the weight gain on the lactose diet was distinctly less than that for the other two sugars. After 32 days, it was only 64 per cent of the gain on glucose and after 21 days, only 61 per cent of the gain on the sucrose diet. On the lactose diets the weight gain curves had a tendency to flatten out considerably before those for glucose or sucrose. The level of the flattening of the lactose curve was 50 per cent below that of the sucrose curve. The voluntary activity of rats on a lactose diet was not greater than that of a group on a glucose diet. Activity, therefore, is not a factor in the poorer nutritive value of lactose. A considerable portion of ingested lactose, approximately from 40 to 50 per cent, may be lost to the rat as far as weight or energy relationships are concerned.