[Show abstract][Hide abstract] ABSTRACT: Resistant starch (RS) is a type of dietary fiber that can improve glucose metabolism, but its effects may be modulated by sex or baseline insulin sensitivity. This study was designed to examine the effect of high-amylose maize resistant starch (HAM-RS2) on insulin sensitivity (S I ) in women, and to determine if S I status affects the response to RS.
This was a randomized, placebo-controlled, double-blind, cross-over study. Participants were 40 healthy, non-diabetic women aged 22–67 years in the normal-weight to obese BMI range (20.6–47.4 kg/m 2 ). Two doses of HAM-RS2 were tested, 15 and 30 g per day, administered in the form of cookies. Participants were randomized to the order in which they received the experimental and placebo product. Each arm was 4 weeks, with a 4-week wash-out period in between. S I was assessed at the end of each 4-week arm of product consumption by frequently-sampled, insulin-modified, intravenous glucose tolerance test and minimal modeling. Participants were categorized as being insulin resistant (IR; S I < 7.8) or insulin sensitive (IS; S I ≥ 7.8) based on Gaussian analysis. The effect of treatment arm on S I was examined by mixed-model analysis within IR and IS sub-groups, using all available data. In addition, S I was examined by ANOVA among just those women who completed all three arms of the study with valid S I results.
Among IR participants, S I was on average ~16 % higher after the 30 g arm when compared to the control arm by mixed-model analysis (n = 40, P < 0.05), and tended to be 23 % higher by ANOVA among women who completed all arms (n = 23, P = 0.06). HAM-RS2 did not affect S I in IS women.
Consumption of HAM-RS2 at 30 g/day in the form of a snack food item was associated with improved insulin sensitivity in women with insulin resistance.
Clinical trials registry number
Full-text · Article · Jan 2016 · Nutrition & Metabolism
[Show abstract][Hide abstract] ABSTRACT: Vascular endothelial function declines with advancing age, due in part to increased oxidative stress and inflammation, and this age-related vascular dysfunction has been identified as an independent risk factor for cardiovascular diseases. This double-blind, placebo-controlled trial investigated the effects of a dietary supplement containing β-hydroxy-β-methylbutyrate (HMB), glutamine and arginine on endothelial-dependent vasodilation of older adults.
A total of 31 community-dwelling men and women aged 65-87 years were randomly assigned to two groups. The treatment group received two doses of the supplement daily (totaling 3 g HMB, 14 g glutamine and 14 g arginine) for 6 months, whereas the control group received an isocaloric placebo. At baseline and week 24, vascular endothelial function was measured by flow-mediated dilation of the brachial artery, and fasting blood samples were obtained to measure high-sensitivity C-reactive protein (hsCRP) and tumor necrosis factor-α (TNF-α).
Paired sample t-tests revealed a 27% increase in flow-mediated dilation among the treatment group (P=0.003), whereas no change was observed in the placebo group (P=0.651). Repeated-measures analysis of variance verified a significant time by group interaction (P=0.038). Although no significant changes were observed for hsCRP or TNF-α, a trend was observed for increasing hsCRP among the placebo group only (P=0.059).
These results suggest that dietary supplementation of HMB, glutamine and arginine may favorably affect vascular endothelial function in older adults. Additional studies are needed to elucidate whether reduced inflammation or other mechanisms may underlie the benefits of supplementation.European Journal of Clinical Nutrition advance online publication, 26 August 2015; doi:10.1038/ejcn.2015.137.
No preview · Article · Aug 2015 · European journal of clinical nutrition
[Show abstract][Hide abstract] ABSTRACT: The role of vitamin D in cardiovascular health remains debated as results have been inconsistent. Previous studies have not considered the bioavailability of 25-hydroxy vitamin D [25(OH)D]. Objectives of our study were to investigate the association between serum concentrations of total, free and bioavailable 25(OH)D and independent predictors of cardiovascular risk such as flow mediated dilatation (FMD) and augmentation index (AIx).
This cross-sectional study included 47 post-menarchal, adolescent females [31 African American (AA) and 16 European American (EA)].
AIx was standardized to a heart rate of 75 beats/min (AIx75). Free and bioavailable 25(OH)D concentrations were calculated from standard formulas.
Mean age of the participants was 15.8±1.4 years and mean body mass index was 23.1±4.0 kg/m2. Serum total 25(OH)D was not associated with FMD, but was positively associated with AIx75 in the adjusted model (rho = 0.4, P = 0.03). AIx75 was positively associated with bioavailable 25(OH)D (rho = 0.4, P = 0.004) and free 25(OH)D (rho = 0.4, P = 0.009) and the associations persisted after adjusting for covariates. In race-specific analyses, total, free and bioavailable 25(OH)D were strongly positively associated with AIx75 in AA (rho = 0.5, 0.4, 0.4, respectively), which persisted even after adjusting for covariates. Whereas in EA there was an inverse association between total 25(OH)D and AIx75 in EA (rho = -0.6), which attenuated after adjusting for covariates.
Circulating total, free and bioavailable 25(OH)D were associated with arterial stiffness in adolescent girls, and these associations were race dependent. Notwithstanding, the implications of associations between vascular function indices and 25(OH)D remains unclear.
[Show abstract][Hide abstract] ABSTRACT: We conducted a study designed to evaluate whether the benefits of intentional weight loss exceed the potential risks in a group of community-dwelling obese older adults who were at increased risk for cardiometabolic disease. The CROSSROADS trial used a prospective randomized controlled design to compare the effects of changes in diet composition alone or combined with weight loss with an exercise only control intervention on body composition and adipose tissue deposition (Specific Aim #1: To compare the effects of changes in diet composition alone or combined with weight loss with an exercise only control intervention on body composition, namely visceral adipose tissue), cardiometabolic disease risk (Specific Aim #2: To compare the effects of a change in diet composition alone or combined with weight loss with an exercise only control intervention on cardiometabolic disease risk), and functional status and quality of life (Specific Aim #3: To compare the effects of a change in diet composition alone or combined with weight loss with an exercise only control intervention on functional status and quality of life). Participants were randomly assigned to one of three groups: Exercise Only (Control) Intervention, Exercise + Diet Quality + Weight Maintenance Intervention, or Exercise + Diet Quality + Weight Loss Intervention. CROSSROADS utilized a lifestyle intervention approach consisting of exercise, dietary, and behavioral components. The development and implementation of the CROSSROADS protocol, including a description of the methodology, detailing specific elements of the lifestyle intervention, assurances of treatment fidelity, and participant retention; outcome measures and adverse event monitoring; as well as unique data management features of the trial results, are presented in this article.
No preview · Article · Nov 2014 · Journal of Nutrition in Gerontology and Geriatrics
[Show abstract][Hide abstract] ABSTRACT: The inability of current recommendations to control the epidemic of diabetes, the specific failure of the prevailing low-fat diets to improve obesity, cardiovascular risk, or general health and the persistent reports of some serious side effects of commonly prescribed diabetic medications, in combination with the continued success of low-carbohydrate diets in the treatment of diabetes and metabolic syndrome without significant side effects, point to the need for a reappraisal of dietary guidelines. The benefits of carbohydrate restriction in diabetes are immediate and well documented. Concerns about the efficacy and safety are long term and conjectural rather than data driven. Dietary carbohydrate restriction reliably reduces high blood glucose, does not require weight loss (although is still best for weight loss), and leads to the reduction or elimination of medication. It has never shown side effects comparable with those seen in many drugs. Here we present 12 points of evidence supporting the use of low-carbohydrate diets as the first approach to treating type 2 diabetes and as the most effective adjunct to pharmacology in type 1. They represent the best-documented, least controversial results. The insistence on long-term randomized controlled trials as the only kind of data that will be accepted is without precedent in science. The seriousness of diabetes requires that we evaluate all of the evidence that is available. The 12 points are sufficiently compelling that we feel that the burden of proof rests with those who are opposed. (C) 2015 The Authors. Published by Elsevier Inc.
[Show abstract][Hide abstract] ABSTRACT: Objective
To determine if consumption of a reduced-carbohydrate (CHO) diet would result in preferential loss of adipose tissue under eucaloric conditions, and whether changes in adiposity were associated with changes in postprandial insulin concentration.
In a crossover-diet intervention, 30 women with PCOS consumed a reduced-CHO diet (41:19:40%energy from CHO:protein:fat) for 8 weeks and a standard diet (55:18:27) for 8 weeks. Body composition by DXA and fat distribution by CT were assessed at baseline and following each diet phase. Insulin AUC was obtained from a solid meal test (SMT) during each diet phase.
Participants lost 3.7% and 2.2% total fat following the reduced-CHO diet and STD diet, resp. (p< 0.05 for difference between diets). The reduced-CHO diet induced a decrease in subcutaneous-abdominal, intra-abdominal, and thigh-intermuscular adipose tissue (-7.1%, -4.6%, and -11.5%, resp.), and the STD diet induced a decrease in total lean mass. Loss of fat mass following the reduced CHO diet arm was associated with lower insulin AUC (p< 0.05) during the SMT.
In women with PCOS, consumption of a diet lower in CHO resulted in preferential loss of fat mass from metabolically harmful adipose depots, whereas a diet high in CHO appeared to promote repartitioning of lean mass to fat mass.
[Show abstract][Hide abstract] ABSTRACT: To test the hypothesis that a breakfast meal with high carbohydrate/low fat results in an earlier increase in postprandial glucose and insulin, a greater decrease below baseline in postprandial glucose, and an earlier return of appetite, compared to a low carbohydrate/high fat meal.
Overweight but otherwise healthy adults (n=64) were maintained on one of two eucaloric diets: high carbohydrate/low fat (HC/LF; 55:27:18% kcals from carbohydrate: fat: protein) versus low carbohydrate/high fat (LC/HF; 43:39:18% kcals from carbohydrate: fat: protein). After 4 weeks of acclimation to the diets, participants underwent a meal test during which circulating glucose and insulin and self-reported hunger and fullness, were measured before and after consumption of breakfast from their assigned diets.
The LC/HF meal resulted in a later time at the highest and lowest recorded glucose, higher glucose concentrations at 3 and 4 hours post-meal, and lower insulin incremental area under the curve. Participants consuming the LC/HF meal reported lower appetite 3 and 4 hours following the meal, a response that was associated with the timing of the highest and lowest recorded glucose.
Modest increases in meal arbohydrate content at the expense of fat content may facilitate weight gain over the long-term by contributing to an earlier rise and fall of postprandial glucose concentrations and an earlier return of appetite.
[Show abstract][Hide abstract] ABSTRACT: Previous studies suggest that circulating 25(OH)D may favorably influence cardiorespiratory fitness and fat oxidation. However, these relationships have not been examined in older adult women of different ethnic groups. The objectives of this study were to determine whether serum 25(OH)D is related to cardiovascular fitness (VO2max) in sedentary women ages ≥60 years and to determine whether these associations differ between African Americans (AA) and European Americans (EA). A secondary aim was to determine whether serum 25(OH)D is correlated with respiratory quotient (RQ) during submaximal exercise. This cross-sectional analysis included 67 AA and EA women ages 60-74 years. VO2max was measured by a modified Bruce graded treadmill protocol, and measurements were adjusted for percent fat and lean body mass assessed by air displacement plethysmography. Indirect calorimetry was used to measure RQ at rest and during four submaximal exercise tests. Fasting blood samples were obtained to quantify serum 25(OH)D. Serum 25(OH)D was associated with VO2max (ml/kg LBM/min) independent of percent body fat (r = 0.316, p = 0.010). However, subgroup analysis revealed that this relationship was specific to AA (r = 0.727, p = 0.005 for AA; r = 0.064, p = 0.643 for EA). In all subjects combined, 25(OH)D was inversely correlated (p < 0.01) with all measures of submaximal RQ. Higher serum 25(OH)D was associated with greater cardiorespiratory fitness in older adult AA women. Among both AA and EA, inverse associations between serum 25(OH)D and RQ suggest that women with higher levels of circulating vitamin D also demonstrated greater fat oxidation during submaximal exercise.
[Show abstract][Hide abstract] ABSTRACT: Context: We hypothesized that similar to the coordinated homeostatic regulation of most hormones, the concentration of free and bioavailable 25-hydroxy vitamin D [25(OH)D] will be tightly controlled by total 25(OH)D and vitamin D binding protein (VDBP); and, that the VDBP concentrations will be associated with insulin resistance status. Objective: Our primary objective was to investigate associations between total, free and bioavailable 25(OH)D and VDBP. We also evaluated the relationships of VDBP with insulin resistance indices. Study design was cross sectional in the setting of a University children's hospital. The relative concentration of bioavailable 25(OH)D to total 25(OH)D [bioavailable 25(OH)D /total 25(OH)D was expressed as a percentage [% bioavailable 25(OH)D]. Results: Subjects were 47, post menarchal, female adolescents, mean age 15.8 ± 1.4 years, mean BMI 23.1 ± 4.0 kg/m(2). Total 25(OH)D was strongly associated with VDBP (rho = 0.57, P = <0.0001). At lower total 25(OH)D concentrations, the concentration of bioavailable 25(OH)D relative to total 25(OH)D was higher (23.8% vs. 14.9%, P<0.0001), whereas the relative concentration of free 25(OH)D was similar (P=0.44). VDBP was inversely associated with fasting insulin (rho=-0.51, P=0.0003) and HOMA-IR (rho=-0.45, P=0.002), and positively with WBISI (rho=0.33, P=0.02); these relationships were persisted after adjusting for percent fat and attenuated after adjusting for race. Conclusion: Our data suggest that, VDBP concentrations are regulated by total 25(OH)D levels to maintain adequate concentrations of bioavailable 25(OH)D. VDBP concentrations are inversely associated with hyperinsulinemia and insulin resistance.Background.
No preview · Article · Oct 2013 · The Journal of Clinical Endocrinology and Metabolism
[Show abstract][Hide abstract] ABSTRACT: Little is known about early coincidental changes in bone and vascular properties, particularly in the context of skeletal anabolism (puberty) versus relative equilibrium (young adulthood). We aimed to determine if subclinical markers of vascular function were associated with bone mineral content (BMC) and to evaluate the contribution of systemic factors in healthy females ages 14-42 years. Endothelial function was assessed by flow mediated dilatation (FMD), arterial stiffness by pulse wave velocity (PWV) and augmentation index (AIx), blood pressure (BP) by sphygmomanometer, BMC by DXA, and systemic factors by fasting blood draw. General linear models controlled for age, race and height indicated a positive association between systolic BP (SBP) and BMC independent of systemic factors. When stratified by age using 19 years as a cut-point, there was an inverse relationship between AIx75 in adolescents with insulin (P<0.10) or inflammatory markers (P<0.10) in statistical models. Conversely, there was a positive relationship between BMC and both PWV and AIx75 in young adults (P<0.05). The link between bone and the vasculature may be life stage-dependent. In the context of a less dynamic microenvironment in young adult females, metabolic factors appear to moderate less of an effect of hemodynamic properties on the skeleton relative to adolescents.
[Show abstract][Hide abstract] ABSTRACT: Historically, obesity was thought to be advantageous for maintaining healthy bones due to the greater bone mineral density observed in overweight individuals. However, recent observations of increased fracture in some obese individuals have led to concern that common metabolic complications of obesity, such as type 2 diabetes, metabolic syndrome, impaired glucose tolerance, insulin resistance, hyperglycemia, and inflammation may be associated with poor bone health. In support of this hypothesis, greater visceral fat, a hallmark of insulin resistance and metabolic syndrome, is associated with lower bone mineral density. Research is needed to determine if and how visceral fat and/or poor metabolic health are causally associated with bone health. Clinicians should consider adding a marker metabolic health, such as waist circumference or fasting plasma glucose concentration, to other known risk factors for osteoporosis and fracture.
No preview · Article · Sep 2013 · Journal of Clinical Densitometry
[Show abstract][Hide abstract] ABSTRACT: Qualitative aspects of diet may affect body composition and propensity for weight gain or loss. We tested the hypothesis that consumption of a relatively low glycemic load (GL) diet would reduce total and visceral adipose tissue under both eucaloric and hypocaloric conditions.
Participants were 69 healthy overweight men and women. Body composition was assessed by DXA and fat distribution by CT scan at baseline, after 8 weeks of a eucaloric diet intervention, and after 8 weeks of a hypocaloric (1000 kcal/day deficit) diet intervention. Participants were provided all food for both phases, and randomized to either a low GL diet (<45 points per 1000 kcal; n = 40) or high GL diet (>75 points per 1000 kcal, n = 29).
After the eucaloric phase, participants who consumed the low GL diet had 11% less intra-abdominal fat (IAAT) than those who consumed the high GL diet (P < 0.05, adjusted for total fat mass and baseline IAAT). Participants lost an average of 5.8 kg during the hypocaloric phase, with no differences in the amount of weight loss with diet assignment (P = 0.39). Following weight loss, participants who consumed the low GL diet had 4.4% less total fat mass than those who consumed the high GL diet (P < 0.05, adjusted for lean mass and baseline fat mass).
Consumption of a relatively low GL diet may affect energy partitioning, both inducing reduction in IAAT independent of weight change, and enhancing loss of fat relative to lean mass during weight loss.