Effects of daily almond consumption (1.5 oz.) on cardiometabolic risk factors in individuals with elevated LDL-cholesterol: lipids and lipoproteins, body composition, and interindividual variation

Open Access
Author:
Berryman, Claire Elizabeth
Graduate Program:
Nutritional Sciences
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
June 10, 2014
Committee Members:
  • Penny Margaret Kris Etherton, Dissertation Advisor
  • Penny Margaret Kris Etherton, Committee Chair
  • Michael Henry Green, Committee Member
  • Amy Griel Preston, Special Member
  • Kathleen Loralee Keller, Committee Member
  • Sheila Grace West, Committee Member
Keywords:
  • abdominal fat
  • cardiometabolic disease
  • diet
  • lipids and lipoproteins
  • cardiovascular disease risk factors
Abstract:
Nut consumption is associated with a decreased risk of cardiovascular disease (CVD) morbidity and mortality. The benefits of nuts are likely due to their unsaturated fatty acid profile, fiber and phytosterol content, and other bioactive nutrients. Reductions in total cholesterol (TC) and LDL-C can be achieved by substituting foods high in unsaturated fat, like nuts, for those high in saturated fat and/or refined carbohydrates. Of all the tree nuts, almonds provide the most fiber, protein, and α-tocopherol per one ounce serving, and clinical evidence consistently shows lipid and lipoprotein improvements with almond consumption. Previous controlled-feeding almond studies employed diet designs that incrementally decreased some or all foods to accommodate the caloric addition of almonds. Thus, almonds have not been evaluated in a controlled-feeding setting using a diet design with only a single, calorie-matched food substitution to assess their effects on cardiometabolic risk factors. We hypothesized that substituting whole almonds for a high-carbohydrate snack, within the context of a low-fat, low-cholesterol background diet, would improve lipids, lipoproteins, and apolipoproteins and decrease abdominal adiposity in adults with elevated LDL-C. A randomized, 2-period (6 wk/period), crossover, controlled-feeding study of 52 individuals with elevated LDL-C (148.0 ± 2.7 mg/dL) was designed to compare a cholesterol-lowering diet with almonds (1.5 oz. of almonds/d) to an identical diet with an isocaloric muffin substitution (no almonds/d). Differences in the nutrient profiles of the control (58% CHO, 15% PRO, 26% total fat) and almond (51% CHO, 16% PRO, 32% total fat) diets were due to nutrients inherent to each snack; diets did not differ in saturated fat or cholesterol. The almond diet, relative to the control diet, decreased non-HDL-C (-6.8 ± 2.4 mg/dL; P = 0.01), LDL-C (-5.2 ± 1.9 mg/dL; P = 0.01), and remnant lipoproteins (-2.8 ± 1.2 mg/dL; P = 0.03); whereas, the control diet decreased HDL-C (-1.8 ± 0.6 mg/dL; P <0.01). Almond consumption also reduced abdominal fat (-0.07 ± 0.03 kg; P = 0.01) and leg fat (-0.12 ± 0.05 kg; P = 0.02), despite no differences in total body weight. It is well established that diets low in saturated fat and cholesterol decrease CVD risk factors, including TC and LDL-C. Consequently, this dietary change also results in decreased HDL-C concentrations. We have shown that a cholesterol-lowering diet incorporating almonds decreases HDL-C to a lesser extent than a traditional low-fat, low-cholesterol diet. HDL has atheroprotective properties that extend beyond absolute HDL-C concentrations, therefore we investigated the dietary effects of almonds on HDL biology and function. We hypothesized that incorporating 1.5 oz./d of almonds in a cholesterol-lowering diet would attenuate decreases in HDL function (i.e. cholesterol efflux) and HDL subspecies that are observed with traditional cholesterol-lowering diets. The almond diet decreased α-1 (-1.4 ± 0.7 vs. -3.4 ± 0.7 mg apoA1/dL; P = 0.001) and the α-1: preβ ratio (-0.06 ± 0.16 vs. -0.55 ± 0.17; P = 0.02) significantly less than the control diet. In addition, the almond diet reduced small HDL α-3 compared to the control diet (-1.0 ± 0.6 vs. 0.1 ± 0.6 mg apoA1/dL; P = 0.04). There were no treatment effects on global or transporter-specific cholesterol efflux. Collectively, almonds reduced LDL-C, remnant lipoproteins, and central adiposity and improved HDL subparticle distribution, all of which are important risk factors for cardiometabolic dysfunction. Daily consumption of almonds, substituted for a high-carbohydrate snack, may be a simple dietary strategy to prevent the onset of cardiometabolic diseases in healthy individuals. Individual responses to dietary treatment varied widely in our study population. We were interested in examining the contributions of interindividual characteristics on treatment response variability. We hypothesized that the almond diet, relative to control, would provide greater benefits in individuals who were normal weight (BMI <25 kg/m2) versus overweight/obese (≥25 kg/m2), individuals with low CRP (<1.0 mg/L) versus those with higher CRP (≥1.0 mg/L), and in individuals with higher cholesterol absorption (lathosterol-to-β-sitosterol ratio <0.95) compared to those with lower cholesterol absorption (≥0.95) on the basis of lipids and lipoproteins. Subgroup analyses revealed that responses to diet were influenced by baseline BMI, CRP, cholesterol absorption, and age categories. In lean participants, the almond diet improved TC (-14.2 ± 4.2 mg/dL; P = 0.01), LDL-C (-12.6 ± 3.3 mg/dL; P <0.01), and HDL-C (3.5 ± 1.0 mg/dL; P = 0.01) compared to the control diet. The almond diet also improved HDL-C in participants with lower relative cardiovascular risk (2.8 ± 0.7 mg/dL; P <0.01) and in those with higher cholesterol absorption (3.3 ± 0.7 mg/dL; P <0.01). In older participants, the almond diet improved TC (-10.7 ± 3.2 mg/dL; P = 0.01) and LDL-C (-9.8 ± 2.5 mg/dL; P <0.01). Participants that were younger, overweight/obese, had an average to higher cardiovascular risk, or lower cholesterol absorption experienced no treatment effects. A better understanding of interindividual responses to diet will allow interventions to be tailored to those who will benefit most, enhancing personalized dietary guidance and improving population-wide dietary recommendations.