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UBC Theses and Dissertations

The nutritional implications of lactose intolerance Tolensky, Arlene Frances


Adult lactose intolerance due to low lactase levels is often associated with varying degrees of abdominal distress ranging from bloating and distension to severe cramps and diarrhea. Recent studies have suggested that these gastrointestinal disturbances may interfere with normal absorption of nutrients in addition to lactose. In order to investigate this possibility, both human and animal studies were conducted. Twenty-three healthy Caucasian adults were used to study the effect of lactose on the absorption of vitamin A, ascorbic acid and protein. Eight of the 23 subjects were lactose intolerant on the basis of a maximum rise of blood glucose of less than 20 mg/100 ml over the fasting blood glucose level after ingestion of 50 g of lactose in 300 ml water. In each study, blood samples were drawn after an overnight fast and at intervals up to k hours after consuming 50 g lactose in an aqueous solution or test meal containing gelatin, vitamin C or vitamin A. Sucrose replaced lactose as a control. The results from the human studies failed to demonstrate that lactose had an effect on the absorption of ascorbic acid, vitamin A or protein in lactose intolerant subjects. It may be that the composition of the test drink which contained fat and protein, may have affected the rate of absorption of the nutrients tested through a delay in gastric emptying time. However, the finding that absorption of vitamin C remained unaffected even when consumed with an aqueous solution of lactose, is attributed to the possibility that the level of ascorbic acid given was too low to show measurable differences in blood levels of that nutrient. To study the effect of lactose on the absorption of calcium, fat and protein, balance studies were conducted using postweaning rats. The experimental groups received either 10?S, 20fo or 30$ lactose diets, while an equivalent amount of sucrose replaced the lactose in the control diets. In addition, postweaning rats were given vitamin A intragastrically with either lactose or sucrose to investigate the effect of lactose on vitamin A absorption. From the balance studies with rats, the results indicate that fecal nitrogen and fat excretion was significantly (p <0,05) higher in all the animals fed lactose as compared to the controls. However, fecal calcium excretion was found to be generally lower for each lactose group relative to the controls, but the difference was statistically significant (p<0.05) only at the 30% level of lactose intake. Improved calcium absorption may have important nutritional implications where dietary calcium intake is low. It appears though, that the level of dietary lactose would most likely have to exceed the limits of normal lactose consumption to have an effect on the absorption of nutrients.

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