Effect of consuming dairy fats on circulating fatty acid profile and metabolism
Increased interest has focused on associations between dietary fatty acids and cardiovascular disease (CVD). Current findings delineating effects of consuming saturated fatty acids (SFA) from dairy on CVD risk remain controversial. The objective of this thesis was to investigate the effects of consuming two types of dairy fat, namely those from cheese and butter on, human plasma and RBC fatty acid profiles, compared with monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA) and carbohydrate (CHO). A secondary objective was to investigate the association between consuming these dietary fatty acids and endogenous de novo fatty acid synthesis. A randomized, full-feeding, crossover, single-blinded clinical trial was conducted at the Institute of Nutrition and Functional Foods (INAF), Laval University and Richardson Centre for Functional Foods and Nutraceuticals (RCFFN), the University of Manitoba. A total of 92 women and men with abdominal obesity and relative low high density lipoprotein cholesterol (HDL-C) levels were randomized into a series of 5 treatments. The duration of each treatment was 4 weeks and separated by at least 4 weeks washout period. For plasma fatty acid profile, total plasma SFA after cheese treatment was found to be higher (P<0.05) than after MUFA, PUFA and CHO treatments, whereas total plasma SFA after butter treatment was only found to be higher (P<0.05) than after MUFA and PUFA treatments. Total plasma MUFA after MUFA treatment was higher (P<0.05) than after all other treatments, and total plasma PUFA after PUFA treatment was higher (P<0.05) than after all other treatments. Unlike plasma fatty acid profile, RBC total SFA after two dairy treatments were not higher than after CHO and PUFA treatments. Consistent with the plasma fatty acid profile, RBC total MUFA after MUFA treatment were found to be higher (P<0.05) than after all other treatments. Similarly, RBC total PUFA after PUFA treatment were higher (P<0.05) than after all other treatments. We did not detect any differences in de novo palmitic acid synthesis across all treatments in the present study. However, we did see a positive correlation between de novo palmitic acid synthesis and body fat mass. In summary, present results suggest that consuming dairy fats, from cheese or butter, can significantly modulate plasma fatty acids in a manner that increases plasma total SFA, including myristic acid (C14:0), pentadecanoic acid (C15:0), palmitic acid (C16:0) and heptadecanoic acid (C17:0). However, the effect of consuming dairy fats on RBC fatty acid profile is relatively minor. Additionally, the de novo fatty acid synthesis data suggests that the quality of dietary fatty acids does not associate with human endogenous fatty acid synthesis; unlike body fat mass.