Effect of a modified milk fat and calcium in purified diets on cholesterol metabolism in hamsters.

Modification of milk fat both by partially replacing saturated FA with oleic acid (18:1) and by increasing calcium intake independently reduces plasma cholesterol. Whether modification of both factors together would synergistically reduce plasma cholesterol is unknown. Seventy-two male golden Syrian hamsters were separated into four diet treatment groups (n = 18/group) and fed ad libitum for 7 wk. Diets contained either modified milk fat (MMF) or regular milk fat (RMF) with either 0.5% (MMF and RMF) or 1.3% calcium (w/w) (MMFC and RMFC). All diets contained 11% test fat, 4% soybean oil, and 0.15% cholesterol (w/w). During the last week, feces were collected for three consecutive days for analysis of fecal FA, cholesterol, and calcium excretion. Overnight-fasted animals were sacrificed, and plasma and livers were collected for lipid analysis. Neither MMF nor additional calcium significantly affected plasma lipids. However, significant interactions existed between MMF and additional calcium for the ratio of LDL cholesterol to HDL cholesterol (LDL/HDL), indicating that increased calcium intake reduced this ratio only in RMF animals. In addition, MMF reduced LDL/HDL relative to RMF. MMF significantly increased hepatic total and esterified cholesterol. Additional calcium significantly increased fecal calcium and saturated FA (SFA) excretion, whereas MMF significantly reduced SFA excretion. RMFC induced the highest excretion of 16:0 among all groups. Replacement of SFA with 18:1 in the MMF reduced the impact of high calcium on LDL/HDL. Additional calcium reduced LDL/HDL only in the presence of RMF, which may be achieved through an increased excretion of 16:0.