Sinead McDonagh
Research Fellow

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Key publications



McDonagh STJ, Wylie LJ, Webster JMA, Vanhatalo A, Jones AM (2018). Influence of dietary nitrate food forms on nitrate metabolism and blood pressure in healthy normotensive adults. Nitric Oxide, 72, 66-74.

Abstract:
Influence of dietary nitrate food forms on nitrate metabolism and blood pressure in healthy normotensive adults.

Inorganic nitrate (NO3-) supplementation has been shown to improve cardiovascular health indices in healthy adults. The purpose of this study was to investigate how the vehicle of NO3- administration can influence NO3- metabolism and the subsequent blood pressure response. Ten healthy males consumed an acute equimolar dose of NO3- (∼5.76 mmol) in the form of a concentrated beetroot juice drink (BR; 55 mL), a non-concentrated beetroot juice drink (BL; 456 mL) and a solid beetroot flapjack (BF; 60 g). A drink containing soluble beetroot crystals (BC; ∼1.40 mmol NO3-) and a control drink (CON; 70 mL deionised water) were also ingested. BP and plasma, salivary and urinary [NO3-] and [NO2-] were determined before and up to 24 h after ingestion. All NO3--rich vehicles elevated plasma, salivary and urinary nitric oxide metabolites compared with baseline and CON (Pandlt;0.05). The peak increases in plasma [NO2-] were greater in BF (371 ± 136 nM) and BR (369 ± 167 nM) compared to BL (283 ± 93 nM; all Pandlt;0.05) and BC (232 ± 51 nM). BR, but not BF, BL and BC, reduced systolic (∼5 mmHg) and mean arterial pressure (∼3-4 mmHg; Pandlt;0.05), whereas BF reduced diastolic BP (∼4 mmHg; P andlt; 0.05). Although plasma [NO2-] was elevated in all conditions, the consumption of a small, concentrated NO3--rich fluid (BR) was the most effective means of reducing BP. These findings have implications for the use of dietary NO3-supplements when the main objective is to maintain or improve indices of cardiovascular health.
 Abstract.  Author URL
(2018). Potential benefits of dietary nitrate ingestion in healthy and clinical populations: a brief review. Eur J Sport Sci, 1-15.

Abstract:
Potential benefits of dietary nitrate ingestion in healthy and clinical populations: a brief review.

This article provides an overview of the current literature relating to the efficacy of dietary nitrate (NO3-) ingestion in altering aspects of cardiovascular and metabolic health and exercise capacity in healthy and diseased individuals. The consumption of NO3--rich vegetables, such as spinach and beetroot, have been variously shown to promote nitric oxide bioavailability, reduce systemic blood pressure, enhance tissue blood flow, modulate muscle O2 utilisation and improve exercise tolerance both in normoxia and in hypoxia, as is commonly observed in a number of disease states. NO3- ingestion may, therefore, act as a natural means for augmenting performance and attenuating complications associated with limited O2 availability or transport, hypertension and the metabolic syndrome. Recent studies indicate that dietary NO3- might also augment intrinsic skeletal muscle contractility and improve the speed and power of muscle contraction. Moreover, several investigations suggest that NO3- supplementation may improve aspects of cognitive performance both at rest and during exercise. Collectively, these observations position NO3- as more than a putative ergogenic aid and suggest that increasing natural dietary NO3- intake may act as a prophylactic in countering the predations of senescence and certain cardiovascular-metabolic diseases.
 Abstract.  Author URL
McDonagh STJ, Vanhatalo A, Fulford J, Wylie LJ, Bailey SJ, Jones AM (2016). Dietary nitrate supplementation attenuates the reduction in exercise tolerance following blood donation. American Journal of Physiology - Heart and Circulatory Physiology, 311(6), H1520-H1529.

Abstract:
Dietary nitrate supplementation attenuates the reduction in exercise tolerance following blood donation

(C) 2016 the American Physiological Society. We tested the hypothesis that dietary nitrate (NO 3 - )-rich beetroot juice (BR) supplementation could partially offset deteriorations in O 2. transport and utilization and exercise tolerance after blood donation. Twenty-two healthy volunteers performed moderate-intensity and ramp incremental cycle exercise tests prior to and following withdrawal of ~450 ml of whole blood. Before donation, all subjects consumed seven 70-ml shots of NO 3 - -depleted BR [placebo (PL)] in the 48 h preceding the exercise tests. During the 48 h after blood donation, subjects consumed seven shots of BR (each containing 6.2 mmol of NO 3 - , n. 11) or PL (n. 11) before repeating the exercise tests. Hemoglobin concentration and hematocrit were reduced by ~8-9% following blood donation (P. andlt;. 0.05), with no difference between the BR and PL groups. Steady-state 02 uptake during moderate-intensity exercise was ~4% lower after than before donation in the. BR group (P. andlt;. 0.05) but was unchanged in the PL group. The ramp test peak power decreased from predonation (341 ± 70 and 331 ± 68 W in PL and BR, respectively) to postdonation (324 ± 69 and 322 ± 66 W in PL and BR, respectively) in both groups (P. andlt;. 0.05). However, the decrement in performance was significantly less in the BR than PL group (2.7% vs. 5.0%, P. andlt;. 0.05). NO 3. supplementation reduced the 02 cost of moderate-inten-sity exercise and attenuated the decline in ramp incremental exercise performance following blood donation. These results have implications for improving functional capacity following blood loss.
 Abstract. Full text
McDonagh STJ, Wylie LJ, Winyard PG, Vanhatalo A, Jones AM (2015). The Effects of Chronic Nitrate Supplementation and the Use of Strong and Weak Antibacterial Agents on Plasma Nitrite Concentration and Exercise Blood Pressure. Int J Sports Med, 36(14), 1177-1185.

Abstract:
The Effects of Chronic Nitrate Supplementation and the Use of Strong and Weak Antibacterial Agents on Plasma Nitrite Concentration and Exercise Blood Pressure.

Chlorhexidine-containing mouthwash (STRONG), which disturbs oral microflora, has been shown to diminish the rise in plasma nitrite concentration ([NO2-]) and attenuate the reduction in resting blood pressure (BP) typically seen after acute nitrate (NO3-) ingestion. We aimed to determine whether STRONG and weaker antiseptic agents attenuate the physiological effects of chronic NO3- supplementation using beetroot juice (BR). 12 healthy volunteers mouth-rinsed with STRONG, non-chlorhexidine mouthwash (WEAK) and deionised water (CON) 3 times a day, and ingested 70 mL BR (6.2 mmol NO3-), twice a day, for 6 days. BP (at rest and during 10 min of treadmill walking) and plasma and salivary [NO3-] and [NO2-] were measured prior to and on day 6 of supplementation. The change in salivary [NO3-] 4 h post final ingestion was higher (Pandlt;0.05) in STRONG (8.7±3.0 mM) compared to CON (6.3±0.9 mM) and WEAK (6.0±3.0 mM). In addition, the rise in plasma [NO2-] at 2 h was lower in STRONG compared with WEAK (by 89±112 nM) and CON (by 200±174 nM) and in WEAK compared with CON (all Pandlt;0.05). Changes in resting BP were not different between conditions (Pandgt;0.05). However, during treadmill walking, the increase in systolic and mean arterial BP was higher 4 h after the final nitrate bolus in STRONG compared with CON (Pandlt;0.05) but not WEAK. The results indicate that both strong and weak antibacterial agents suppress the rise in plasma [NO2-] observed following the consumption of a high NO3- diet and the former can influence the BP response during low-intensity exercise.
 Abstract.  Author URL

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