Eight normolipidemic males ingested on separate days and in a random order five mixed meals containing 0, 15, 30, 40, or 50 g fat. Fasting and postprandial blood samples were obtained for 7 h and chylomicrons and lipoproteins were isolated. The nonfat and 15-g fat meals did not generate noticeable postprandial variations except for HDL phospholipids (P < 0.05). The serum and chylomicron triacylglycerol responses obtained after the meals correlated positively with the amount of fat ingested and peaked after 2-3 h. Serum free cholesterol and phospholipids increased and esterified cholesterol decreased postprandially in a dose-response manner. At the same time, triacylglycerol-rich-lipoprotein triacylglycerols, esterified cholesterol, LDL free cholesterol, HDL triacylglycerols, phospholipids, and free cholesterol increased whereas LDL and HDL esterified cholesterol decreased when the amount of ingested fat increased. The data showed that increasing the amount of fat in the usual range of ingestion (0-50 g) led to stepwise increases in the postprandial rise of chylomicron and serum triacylglycerols and induced marked changes in serum lipoproteins postprandially. The existence of a no-effect level of dietary fat (15 g) on postprandial lipemia and lipoproteins in healthy adults was shown.
Eight normolipidemic males ingested a meal containing either 42 g fat or 31 g fat in the form of emulsions (9.0 and 9.2 m2) and a fixed amount of retinyl palmitate. Fasting and postmeal blood samples were obtained for 7 h. Serum and chylomicron triglyceride responses were related to the amount of fat ingested and peaked after 2-3 h. The chylomicron retinyl palmitate response was lower (P < or = 0.05) with the 31-g fat supply. After the 42-g fat intake, but not after the 31-g fat intake, serum free cholesterol and phospholipids increased and esterified cholesterol decreased postprandially. Significantly different responses were observed after both meals for low-density-lipoprotein (LDL) free cholesterol, very-low-density-lipoprotein (VLDL) and LDL esterified cholesterol, and high-density-lipoprotein (HDL) phospholipids. These data show that ingesting 31 g instead of 42 g fat in a meal reduces postmeal lipoprotein variations and suggest that a threshold level of dietary fat should be overcome to promote significant postprandial changes in lipoprotein particles.
Six normolipidemic males ingested on separate days a low-fiber test meal [2.8 g dietary fiber (TDF)] containing 70 g fat and 756 mg cholesterol, enriched or not with 10 g TDF as oat bran, rice bran, or wheat fiber or 4.2 g TDF as wheat germ. Fasting and postmeal blood samples were obtained for 7 h and chylomicrons were isolated. Adding fibers to the test meal induced no change in serum glucose or insulin responses. The serum triglyceride response was lower (P less than or equal to 0.05) in the presence of oat bran, wheat fiber, or wheat germ and chylomicron triglycerides were reduced with wheat fiber. All fiber sources reduced chylomicron cholesterol. Cholesterolemia decreased postprandially for 6 h and was further lowered in the presence of oat bran. Serum apolipoprotein (apo) A-1 and apo B concentrations were not affected. Thus, dietary fibers from cereals may reduce postprandial lipemia in humans to a variable extent.
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