Increasing the dietary polyunsaturated fat content alters whole-body utilization of 16:0 and 10:0

Six healthy adult males were fed four different diets to determine the effects of the quantity of fat (30% or 40% of energy as fat) and type of fat (polyunsaturated or saturated) on utilization of fatty acids. Each diet was fed for 15 d. The ratio of dietary polyunsaturated to saturated fat (P:S) was formulated at either 0.2 or 1.0 at both fat intakes. Subjects provided breath tests to measure background 13C and response to [1-13C]10:0 and [1-13C]16:0 fed with a test meal. Increasing the P:S increased whole-body oxidation of labeled 10:0 by 30% after consumption of both low- and high-fat diets. When labeled 16:0 was fed, the amount of 13C excreted in breath increased by a factor of 2.4 after the low-fat diet with a high P:S compared with the diet with a low P:S. The results suggest that the amount and type of fat in the diet affect utilization of individual fatty acids in normal subjects.