Some Unique Properties of Lactose as a Dietary Carbohydrate

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Abstract
Young rats weighing 50-60 g. were fed ad libitum purified diets containing 5% fat in which USP lactose was substituted for cornstarch at levels of 5, 10, 15, 20, 25, 30, 40, and 50% of the total ration. Feed consumption was recorded and the animals were weighed and observed for symptoms of lactose feeding 3 times each wk. for 12 wks. Up to and including 30% lactose, these rations equaled the basal ration (no lactose) in growth and food utilization. At the 40 and 50% levels, growth was less, and at 50% food utilization was less efficient than on the basal ration. Symptoms of lactose feeding, diarrhea and/or "pot-bellies," were observed first at the 20% level and became progressively more severe and more persistent as the percentage of lactose in the ration was increased. The capacity of the rats to utilize lactose without suffering from diarrhea was increased through repeated daily intake of rations containing lactose. By feeding rations containing a mixture of equal parts glucose and galactose at levels equivalent to 15, 30, and 50% lactose, the lactose linkage was found responsible for the symptoms observed on rations, with higher percentages of lactose. At levels of 30, and 50%, growth was less and food utilization more efficient on the diets containing lactose than on the rations containing equivalent amts. of the mixture of the 2 simple sugars.