Effects of diets low in SFA and with varying MUFA and PUFA profiles on body composition and HDL function in individuals with or at risk for metabolic syndrome

Open Access
Author:
Liu, Xiaoran
Graduate Program:
Nutritional Sciences
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
December 11, 2014
Committee Members:
  • Penny Margaret Kris Etherton, Dissertation Advisor
  • Penny Margaret Kris Etherton, Committee Chair
  • Sheila Grace West, Committee Member
  • Michael Henry Green, Committee Member
  • Joshua D Lambert, Committee Member
Keywords:
  • SFA MUFA body composition HDL function abdominal fat mass cardio
Abstract:
Monounsaturated fatty acids (MUFA) decrease risk of metabolic syndrome (MetS). There is evidence that vegetable oils high in MUFA lower CVD risk in individuals with MetS. A multi-center, double blind, randomized, 5-period crossover, controlled feeding study was conducted. Subjects (n=101: 51 women, 50 men) were fed an isocaloric heart healthy diet containing one of the five treatment oils incorporated in a smoothie for 4 weeks followed by a 4 weeks break between experimental diets. The five vegetable oils were: Canola oil (62.8% MUFA, 29.3% PUFA: 19.5% LA, 10% ALA), CanolaOleic oil (72% MUFA, 17% PUFA: 15% LA, 2% ALA), CanolaDHA (63.8% MUFA, 13% LA, 6% DHA), corn/safflower oil (69.3% LA, 17.6% MUFA) and flax/safflower oil (69.4% PUFA: 37.5% LA, 32% ALA, 17.9% MUFA). The first study was designed to evaluate the efficacy of five vegetable oils (low in saturated fatty acid (SFA) with varying unsaturated fatty acid profiles) on abdominal fat mass in subjects with or at risk for MetS. After four weeks, reductions in abdominal fat mass were observed when the Canola (-54.59 g, p=0.0264) and CanolaOleic oil diets (-66.09 g, p=0.0245) were compared with the Flax/Saff oil diet. The reduction of android fat mass from baseline in response to the Canola (p=0.042) and CanolaOleic (p=0.007) were both significant. There was no difference in changes of abdominal fat mass from baseline for the CanolaDHA, Corn/Saff and Flax/Saff oil diets. The android to gynoid fat mass ratio was decreased in males after the CanolaOleic oil diet compared with the Flax/Saff oil diet (0.71 versus 0.73, p=0.0067). Attenuation of central obesity was associated with a reduction in blood pressure in response to the Canola (SBP r = 0.26, p=0.062; DBP r=0.38, p=0.0049) and CanolaOleic oil diets (SBP r = 0.39 p=0.004; DBP r=0.45, p=0.0006). Moreover, the decrease in central obesity was associated with a reduction in TG on the CanolaOleic oil diet (r = 0.42, p=0.0017). The second study was designed to investigate the effects of five vegetable oils on HDL function measured via cholesterol efflux capacity. The Canola, CanolaOleic, CanolaDHA, Corn/Saff and Flax/Saff oil diets increased serum mediated CEx capacity from THP-1 macrophages by 39.1%, 33.6%, 55.3%, 49.2% and 50.7% respectively, compared to baseline (p<0.05 for all). Weight status was an independent predictor of the serum mediated CEx capacity. Participants with a normal BMI had a greater increase in CEx capacity compared with overweight and obese participants. Waist circumference and abdominal adiposity were negatively correlated with serum mediated CEx capacity (r = -0.25, p = 0.012, r = -0.33, p = 0.017, respectively). The third study was designed to explore the relationship among VAT, SAT and anthropometric measurements in a subgroup of study participants (n=14). Regression analysis demonstrated that at baseline, in both males and females, CRP was positively correlated with VAT mass (r = 0.92, p < 0.0001). Waist circumference was positively correlated with SAT mass (r = 0.59, p = 0.034). In addition, BMI was positively correlated with SAT mass (r = 0.83, p = 0.0008). There were no correlations for CRP level and SAT mass; waist circumference and VAT mass; and BMI and VAT mass. Overall, the results showed that two of high MUFA diets (Canola and CanolaOleic) had beneficial effects on reducing abdominal fat mass and improving MetS risk in individuals with or at risk for MetS. All diets low in SFA increased CEx capacity indicating an improvement in HDL functionality. Waist circumference was positively correlated with SAT but not VAT. VAT mass was associated with increased inflammation status.