Carbohydrate ingestion attenuates the reduction in complex cognitive function and cerebral blood flow during prolonged passive heat stress in humans

PURPOSE

To determine whether carbohydrate ingestion would reduce cognitive dysfunction in humans following long duration passive heat stress (PHS) versus consuming electrolytes alone.

METHODS

Fifteen young (27 ± 4 y) healthy adults were exposed to 120 min of PHS through the use of a liquid perfused suit (50 °C) on two randomized visits. Subjects consumed fluids supplemented with electrolytes (E) or electrolytes + carbohydrates (E + C). Pre- and post-heat stress, body mass (BM) and plasma osmolality (pOsm) were measured. Heart rate (HR), blood pressure (BP), Physiological Strain Index (PSI), core temperature (Tc), plasma glucose, respiration rate (RR), end-tidal CO2 (PetCO2) and internal carotid artery (ICA) blood flow were recorded at baseline and every 15 min of heat stress. Cognitive function was assessed via the Automated Neuropsychological Assessment Metric at baseline and at 30- and 120 min during heat stress.

RESULTS

There were no significant differences between fluid conditions for BM, pOsm, PSI, Tc, RR or PetCO2. Plasma glucose was ∼75% greater in the E + C condition compared to the E condition after 90 min of PHS (P < 0.05). Cognitive function (120 min) was impaired following PHS only in E condition (P < 0.05) and performance on complex cognitive tasks were better by ∼22-340% in the E + C vs. E (P < 0.05). Compared to the E condition, HR and BP were lower and ICA blood flow, vascular conductance, and glucose delivery was ∼90% greater in the E + C after 90 min of PHS (P < 0.05).

CONCLUSIONS

These data are the first to demonstrate that carbohydrate ingestion may have a protective effect on cognitive function during long duration PHS. Furthermore, this protection was associated with preserved ICA blood flow and glucose delivery to the brain.

Blueberries Improve Endothelial Function in Postmenopausal Women With Above-Normal Blood Pressure via Reductions in Oxidative Stress

Objectives

Research suggests blueberries and their (poly)phenols may improve endothelial dysfunction, a major risk factor for cardiovascular disease (CVD). The objective of this study was to investigate the impact of consuming 22 g/day for 12 weeks of freeze-dried highbush blueberry powder on endothelial function and other measures of cardiovascular health, oxidative stress, and circulating (poly)phenol metabolites in postmenopausal women with above-normal blood pressure.

Methods

We performed a randomized, double-blind, placebo-controlled, parallel-arm trial in estrogen-deficient postmenopausal women aged 45–65 years with elevated blood pressure or stage 1-HTN. Endothelial function was assessed as brachial artery flow-mediated dilation (FMD) and normalized to individual shear rate area under the curve (FMD/SR_AUC) to control for inter-individual variability in reactive hyperemia-induced shear stress. To assess whether improvements in FMD were mediated by reduced oxidative stress, FMD was assessed before and after intravenous infusion of a supra-physiologic dose of ascorbic acid. Blood pressure, arterial stiffness, and plasma (poly)phenol metabolites were also assessed.

Results

A total of 43 women completed the trial (n = 32 for endothelial function). Compliance in the Blueberry and Placebo groups were 93% and 91%, respectively. Mean total plasma (poly)phenol metabolite concentrations were increased at 4 (250,053 nmol/L, P < 0.05) and 8 (303,053 nmol/L, P < 0.05) weeks in the Blueberry group compared to baseline (125,798 nmol/L) with a strong trend at 12 weeks (227,971 nmol/L, P < 0.05), and no changes in Placebo. Blood pressure and arterial stiffness were unchanged with both treatments. At 12 weeks, FMD/SR_AUC was increased by 96% from baseline (P < 0.05) in the Blueberry group but unchanged in Placebo, and changes in FMD/SR_AUC from baseline to 12 weeks were higher (P < 0.05) than Placebo. The response in FMD/SR_AUC to ascorbic acid infusion was lower (P < 0.05) at 12 weeks compared to baseline in the Blueberry group but not Placebo.

Conclusions

These findings suggest blueberries improve endothelial function, and is mediated, in part, by reduced oxidative stress in postmenopausal women with above-normal blood pressure, a high-risk population for developing CVD.

Funding Sources

US Highbush Blueberry Council and USDA National Institute of Food and Agriculture.

Acute differences in pulse wave velocity, augmentation index, and central pulse pressure following controlled exposures to cookstove air pollution in the Subclinical Tests of Volunteers Exposed to Smoke (SToVES) study

Household air pollution emitted from solid-fuel cookstoves used for domestic cooking is a leading risk factor for morbidity and premature mortality globally. There have been attempts to design and distribute lower emission cookstoves, yet it is unclear if they meaningfully improve health. Using a crossover design, we assessed differences in central aortic hemodynamics and arterial stiffness following controlled exposures to air pollution emitted from five different cookstove technologies compared to a filtered air control. Forty-eight young, healthy participants were assigned to six 2-h controlled treatments of pollution from five different cookstoves and a filtered air control. Each treatment had a target concentration for fine particulate matter: filtered air control = 0 μg/m³, liquefied petroleum gas = 10 μg/m³, gasifier = 35 μg/m³, fan rocket = 100 μg/m³, rocket elbow = 250 μg/m³, three stone fire = 500 μg/m³. Pulse wave velocity (PWV), central augmentation index (AIx), and central pulse pressure (CPP) were measured before and at three time points after each treatment (0, 3, and 24 h). Linear mixed models were used to assess differences in the outcomes for each cookstove treatment compared to control. PWV and CPP were marginally higher 24 h after all cookstove treatments compared to control. For example, PWV was 0.15 m/s higher (95% confidence interval: -0.02, 0.31) and CPP was 0.6 mmHg higher (95% confidence interval: -0.8, 2.1) 24 h after the three stone fire treatment compared to control. The magnitude of the differences compared to control was similar across all cookstove treatments. PWV and CPP had no consistent trends at the other post-treatment time points (0 and 3 h). No consistent trends were observed for AIx at any post-treatment time point. Our findings suggest higher levels of PWV and CPP within 24 h after 2-h controlled treatments of pollution from five different cookstove technologies. The similar magnitude of the differences following each cookstove treatment compared to control may indicate that acute exposures from even the cleanest cookstove technologies can adversely impact these subclinical markers of cardiovascular health, although differences were small and may not be clinically meaningful.