Effect of Incorporating 1 Avocado Per Day Versus Habitual Diet on Visceral Adiposity: A Randomized Trial.

Background Excess visceral adiposity is associated with increased risk of cardiometabolic disorders. Short-term well-controlled clinical trials suggest that regular avocado consumption favorably affects body weight, visceral adiposity, and satiety. Methods and Results The HAT Trial (Habitual Diet and Avocado Trial) was a multicenter, randomized, controlled parallel-arm trial designed to test whether consuming 1 large avocado per day for 6 months in a diverse group of free-living individuals (N=1008) with an elevated waist circumference compared with a habitual diet would decrease visceral adiposity as measured by magnetic resonance imaging. Secondary and additional end points related to risk factors associated with cardiometabolic disorders were assessed. The primary outcome, change in visceral adipose tissue volume during the intervention period, was not significantly different between the Avocado Supplemented and Habitual Diet Groups (estimated mean difference (0.017 L [-0.024 L, 0.058 L], P=0.405). No significant group differences were observed for the secondary outcomes of hepatic fat fraction, hsCRP (high-sensitivity C-reactive protein), and components of the metabolic syndrome. Of the additional outcome measures, modest but nominally significant reductions in total and low-density lipoprotein cholesterol were observed in the Avocado Supplemented compared with the Habitual Diet Group. Changes in the other additional and post hoc measures (body weight, body mass index, insulin, very low-density lipoprotein concentrations, and total cholesterol:high-density lipoprotein cholesterol ratio) were similar between the 2 groups. Conclusions Addition of 1 avocado per day to the habitual diet for 6 months in free-living individuals with elevated waist circumference did not reduce visceral adipose tissue volume and had minimal effect on risk factors associated with cardiometabolic disorders. Registration URL: https://clinicaltrials.gov; Unique identifier: NCT03528031.

Comparison of the Postprandial Metabolic Fate of U-13C Stearic Acid and U-13C Oleic Acid in Postmenopausal Women.

OBJECTIVE: Compare the postprandial fatty acid metabolism of isotopically labeled stearate (U-13C18:0) and oleate (U-13C18:1). Approach and Results: In conjunction with a randomized-controlled crossover trial, 6 hypercholesterolemic postmenopausal women (≥50 years; body mass index: 25.6±3.0 kg/m2; LDL [low-density lipoprotein]-cholesterol ≥110 mg/dL) consumed isocaloric diets enriched in 18:0 or 18:1 (10%-15% E) for 5 weeks each. On day 1 of week 5, following a 12-hour fast, participants receive their experimental diet divided into 13 hourly meals beginning at 8 am. U-13C18:0 or U-13C18:1 was incorporated into the 1:00 pm meal (1.0 mg/kg body weight). Serial blood and breath samples were collected over 12 hours and fasting samples at 24 and 48 hours. Plasma and lipid subfraction fatty acid profiles were assessed by gas chromatography-flame ionization detector, isotope-enrichment by liquid chromatography time-of-flight mass spectrometry, and fatty acid oxidation rate (expired 13CO2) by isotope ratio mass spectrometry. Both diets resulted in similar plasma LDL-cholesterol concentrations. Kinetic curves showed that U-13C18:0 had a higher plasma area under the curve (66%), lower plasma clearance rate (-46%), and a lower cumulative oxidation rate (-34%) than U-13C18:1. Three labeled plasma metabolites of U-13C18:0 were detected: 13C16:0, 13C16:1, and 13C18:1. No plasma metabolites of U-13C18:1 were detected within the study time-frame. Higher incorporation of 18:0 in cholesteryl ester and triglyceride fractions was observed on the 18:0 compared with the 18:1 diet. CONCLUSIONS: The neutrality of 18:0 on plasma LDL-cholesterol concentrations is not attributable to a single factor. Compared with 18:1, 18:0 had higher plasma area under the curve because of lower clearance and oxidation rates, underwent both a direct and a multistage conversion to 18:1, and was preferentially incorporated into cholesteryl esters and triglycerides.

Exploring changes in the human gut microbiota and microbial-derived metabolites in response to diets enriched in simple, refined, or unrefined carbohydrate-containing foods: a post hoc analysis of a randomized clinical trial.

BACKGROUND: Dietary carbohydrate type may influence cardiometabolic risk through alterations in the gut microbiome and microbial-derived metabolites, but evidence is limited. OBJECTIVES: We explored the relative effects of an isocaloric exchange of dietary simple, refined, and unrefined carbohydrate on gut microbiota composition/function, and selected microbial metabolite concentrations. METHODS: Participants [n = 11; age: 65 ± 8 y; BMI (in kg/m2): 29.8 ± 3.2] were provided with each of 3 diets for 4.5 wk with 2-wk washout, according to a randomized, crossover design. Diets [60% of energy (%E) carbohydrate, 15%E protein, and 25%E fat] differed in type of carbohydrate. Fecal microbial composition, metatranscriptomics, and microbial-derived SCFA and secondary bile acid (SBA) concentrations were assessed at the end of each phase and associated with cardiometabolic risk factors (CMRFs). RESULTS: Roseburia abundance was higher (11% compared with 5%) and fecal SBA concentrations were lower (lithocolic acid -50% and deoxycholic acid -64%) after consumption of the unrefined carbohydrate diet relative to the simple carbohydrate diet [false discovery rate (FDR): all P < 0.05), whereas Anaerostipes abundance was higher (0.35% compared with 0.12%; FDR: P = 0.04) after the simple carbohydrate diet relative to the refined carbohydrate diet. Metatranscriptomics indicated upregulation of 2 cellular stress genes (FDR: P < 0.1) after the unrefined carbohydrate diet compared with the simple carbohydrate or refined carbohydrate diets. The microbial expression of 3 cellular/oxidative stress and immune response genes was higher (FDR: P < 0.1) after the simple carbohydrate diet relative to the refined carbohydrate diet. No significant diet effect was observed in fecal SCFA concentrations. Independent of diet, we observed 16 associations (all FDR: P < 0.1) of taxon abundance (15 phylum and 1 genera) with serum inflammatory markers and also with fecal SCFA and SBA concentrations. CONCLUSIONS: Consuming an unrefined carbohydrate-rich diet had a modest effect on the gut microbiome and SBAs, resulting in favorable associations with selected CMRFs. Simple carbohydrate- and refined carbohydrate-rich diets have distinctive effects on the gut microbiome, suggesting differential mechanisms mediate their effects on cardiometabolic health. This trial was registered at clinicaltrials.gov as NCT01610661.

Simplified method for the measurement of plasma alkylresorcinols: Biomarkers of whole-grain intake.

RATIONALE: Consumption of whole grains is negatively associated with cardiovascular disease (CVD) risk but quantification of whole-grain intake is challenging. Alkylresorcinols (ARs) are biomarkers of whole-grain intake. Current methods for AR quantification involve a time-consuming multi-step separation process that hampers applicability in large-scale studies. METHODS: We developed a streamlined method to quantify ARs in human plasma based on protein precipitation and direct injection into an ultra-high-performance liquid chromatograph coupled to a quadrupole time-of-flight mass spectrometer operating in atmospheric pressure chemical ionization negative ion mode. RESULTS: Separation of five major ARs was achieved, with linearity in the 5 to 550 nmol/L range and a lower limit of detection (LOD) of 0.5 nmol/L and quantification (LOQ) of 5 nmol/L. The within-run and between-run precision and accuracy were below 15%, and recoveries above 90%. Once validated, the method was applied to measure concentrations of plasma ARs in subjects who participated in a randomized, crossover trial evaluating the effect of carbohydrate type on CVD risk factors. The unrefined carbohydrate diet with the highest fiber content resulted in the highest plasma AR concentration (93 ± 78 nmol/L), and was significantly different (p <0.01) from lower fiber diets (18 ± 26 nmol/L and 19 ± 26 nmol/L, simple and unrefined carbohydrate, respectively). CONCLUSIONS: This method offers a simplified approach to measure concentrations of plasma ARs as an objective biomarker of whole-grain intake that can be applied to large-scale cohort studies.

Supplementation with Seabuckthorn Oil Augmented in 16:1n-7t Increases Serum Trans-Palmitoleic Acid in Metabolically Healthy Adults: A Randomized Crossover Dose-Escalation Study.

BACKGROUND: In animal models cis-palmitoleic acid (9-hexadecenoic acid; 16:1n-7c), a lipokine, improves insulin sensitivity, inflammation, and lipoprotein profiles; in humans trans-palmitoleic acid (16:1n-7t) has been associated with lower incidence of type 2 diabetes. The response to dose-escalation of supplements containing cis- and trans-palmitoleic acid has not been evaluated. OBJECTIVES: We examined dose-escalation effects of oral supplementation with seabuckthorn oil and seabuckthorn oil augmented in 16:1n-7t on serum phospholipid fatty acids (PLFAs). METHODS: Thirteen participants (7 women and 6 men; age 48 ± 16 y, BMI 30.4 ± 3.7 kg/m2) participated in a randomized, double-blind, crossover, dose-escalation trial of unmodified seabuckthorn oils relatively high in 16:1n-7c (380, 760, and 1520 mg 16:1n-7c/d) and seabuckthorn oils augmented in 16:1n-7t (120, 240, and 480 mg 16:1n-7t/d). Each of the 3 escalation doses was provided for 3 wk, with a 4-wk washout period between the 2 supplements. At the end of each dose period, fasting blood samples were used to determine the primary outcomes (serum concentrations of the PLFAs 16:1n-7t and 16:1n-7c) and the secondary outcomes (glucose homeostasis, serum lipids, and clinical measures). Trends across doses were evaluated using linear regression. RESULTS: Compared with baseline, supplementation with seabuckthorn oil augmented in 16:1n-7t increased phospholipid 16:1n-7t by 26.6% at the highest dose (P = 0.0343). Supplementation with unmodified seabuckthorn oil resulted in a positive trend across the dose-escalations (P-trend = 0.0199). No significant effects of either supplement were identified on blood glucose, insulin, lipids, or other clinical measures, although this dosing study was not powered to detect such effects. No carryover or adverse effects were observed. CONCLUSIONS: Supplementation with seabuckthorn oil augmented in 16:1n-7t and unmodified seabuckthorn oil moderately increased concentrations of their corresponding PLFAs in metabolically healthy adults, supporting the use of supplementation with these fatty acids to test potential clinical effects in humans.This trial was registered at clinicaltrials.gov as NCT02311790.

Comparison of diets enriched in stearic, oleic, and palmitic acids on inflammation, immune response, cardiometabolic risk factors, and fecal bile acid concentrations in mildly hypercholesterolemic postmenopausal women-randomized crossover trial.

BACKGROUND: Direct comparisons between SFAs varying in chain length, specifically palmitic acid (16:0) and stearic acid (18:0), relative to the latter's metabolic product, oleic acid (18:1), on cardiometabolic risk factors are limited. OBJECTIVE: The aim of this study was to determine the relative comparability of diets enriched in palmitic acid, stearic acid, and oleic acid on inflammation and coagulation markers, T lymphocyte proliferation/ex-vivo cytokine secretion, plasma cardiometabolic risk factors, and fecal bile acid concentrations. METHODS: Hypercholesterolemic postmenopausal women (n = 20, mean ± SD age 64 ± 7 y, BMI 26.4 ± 3.4 kg/m2, LDL cholesterol ≥ 2.8 mmol/L) were provided with each of 3 diets [55% energy (%E) carbohydrate, 15%E protein, 30%E fat, with ∼50% fat contributed by palmitic acid, stearic acid, or oleic acid in each diet; 5 wk/diet phase] using a randomized crossover design with 2-wk washouts between phases. Outcome measures were assessed at the end of each phase. RESULTS: Fasting LDL-cholesterol and non-HDL-cholesterol concentrations were lower after the stearic acid and oleic acid diets than the palmitic acid diet (all P < 0.01). Fasting HDL-cholesterol concentrations were lower after the stearic acid diet than the palmitic acid and oleic acid diets (P < 0.01). The stearic acid diet resulted in lower lithocholic acid (P = 0.01) and total secondary bile acid (SBA) concentrations (P = 0.04) than the oleic acid diet. All other outcome measures were similar between diets. Lithocholic acid concentrations were positively correlated with fasting LDL-cholesterol concentrations (r = 0.33; P = 0.011). Total SBA, lithocholic acid, and deoxycholic acid concentrations were negatively correlated with fasting HDL cholesterol (r = -0.51 to -0.44; P < 0.01) concentrations and positively correlated with LDL cholesterol:HDL cholesterol (r = 0.37-0.54; P < 0.01) ratios. CONCLUSIONS: Dietary stearic acid and oleic acid had similar effects on fasting LDL-cholesterol and non-HDL-cholesterol concentrations and more favorable ones than palmitic acid. Unlike oleic acid, the hypocholesterolemic effect of stearic acid may be mediated by inhibition of intestinal hydrophobic SBA synthesis. These findings add to the data suggesting there should be a reassessment of current SFA dietary guidance and Nutrient Facts panel labeling.This trial was registered at clinicaltrials.gov as NCT02145936.

Effect of Dietary Carbohydrate Type on Serum Cardiometabolic Risk Indicators and Adipose Tissue Inflammatory Markers.

Context and Objective: Direct comparisons between types of dietary carbohydrate in terms of cardiometabolic risk indicators are limited. This study was designed to compare the effects of an isocaloric exchange of simple, refined, and unrefined carbohydrates on serum cardiometabolic risk indicators, adipose tissue inflammatory markers, and peripheral blood mononuclear cell (PBMC) fractional cholesterol efflux. Design, Participants, and Measures: Participants [postmenopausal women and men (N = 11), 65 ± 8 years, body mass index 29.8 ± 3.2 kg/m2, low-density lipoprotein (LDL) cholesterol ≥2.6 mmol/L] were provided with diets (60% energy from total carbohydrate, 15% from protein, 25% from fat) for 4.5 weeks in a randomized crossover design, with 2-week washout periods. The variable component was an isocaloric exchange of simple, refined, or unrefined carbohydrate-containing foods. Serum lipoprotein, glucose, insulin, and inflammatory marker concentrations were measured. Abdominal subcutaneous adipose tissue was aspirated to assess macrophage and inflammatory marker gene expression and ex vivo cytokine secretion, and PBMCs were isolated to assess ex vivo fractional cholesterol efflux. Results: Fasting serum LDL and non-high-density lipoprotein (HDL) cholesterol concentrations were higher after the refined compared with simple or unrefined carbohydrate-enriched diets (P < 0.01). Other serum measures, ex vivo fractional cholesterol efflux and adipose tissue gene expression and ex vivo cytokine secretion, were similar between diets. Conclusions: Diets enriched in refined compared with simple or unrefined carbohydrate resulted in higher fasting serum LDL and non-HDL cholesterol concentrations but had little effect on other cardiometabolic risk indicators. This small study raises the intriguing possibility that refined carbohydrate may have unique adverse effects on cardiometabolic risk indicators distinct from simple and unrefined carbohydrate.