Objective: To study small bowel cholesterol absorption and sterol excretion in order to explain possible serum cholesterol-lowering mechanisms of low-fat milk products.
Design: Two 24-h sterol balance studies with 1 litre of low-fat milk or one litre of fermented milk, in random order, added to a controlled diet. [3H]Cholesterol absorption was measured during each period. The results were compared to those on two 24-h periods with isocaloric amounts of lemonade given to the same basic diet, before and after the study. One litre of the two milk products was also consumed in addition to their normal diets in a cross-over design of 3 weeks and with run-in and run-out periods of 2 weeks each with 1000 ml of lemonade preceding the balance studies:
Setting: Outpatient clinic, where the subjects were eating their meals during the day and ileostomy bags collected.
Subjects: Nine ileostomy subjects, who have earlier participated in similar studies, volunteered for the study. All subjects completed the study.
Results: Cholesterol absorption was highest (66%) in the lemonade period, intermediate in the low-fat milk period (61%) and lowest in the fermented low-fat period (55%) (P < 0.05 for differences). Net cholesterol excretion (excretion minus intake) and calculated endogenous cholesterol excretion were significantly (P < 0.05 for differences) higher in the low-fat milk period than in the lemonade period and the fermented low-fat milk period. No significant change in serum cholesterol was, however, seen after 3 weeks on each milk regimen.
Conclusion: Assimilation of cholesterol by microorganisms could possibly explain the reduced uptake of cholesterol with fermented milk. The mechanism behind the increased endogenous cholesterol excretion, induced by low-fat milk, is unclear.