Magnesium: Supplementation, absorption and effect on blood pressure and exercise

Introduction Magnesium is required by the human body in modest amounts for the maintenance of health and optimal functioning. Objectives This portfolio of work sets out to investigate whether magnesium supplementation has hypotensive effects and to determine if habitual dietary magnesium intake or loading strategies modulate the effects of magnesium supplementation. The habitual dietary magnesium intake of hypertensive patients was also examined to ascertain adequacy of dietary magnesium in this cohort. A meta-analysis was performed on the effect of magnesium supplementation on blood pressure. Other variables such as dosage, duration and study design were considered and findings from the meta-analysis used to influence future work. A further objective was to examine the effect of supplementation on aerobic and resistance exercise and subsequent recovery. Finally, the efficacy of an alternative means of magnesium delivery in the form of a transdermal magnesium cream was investigated. Methods A 300 mg.day-1 elemental magnesium aspartate or magnesium citrate was used as a supplementation in studies 1,2,4 and 5. Participants were instructed to continue with their normal diet and for study 6 participants were required to eat the same foods for the 24 hours prior to both laboratory blood taking sessions. With the exception of the meta-analysis, food diaries were kept for various lengths of time, detailed in the publications. Aerobic and resistance exercise protocols were carried out in studies 1,2 and 4, with both performance and cardiovascular parameters investigated for any effect from supplementation. Where supplementation was in the form of a transdermal cream, this was applied to the torso and absorption of the cream was determined by investigating changes in serum and urinary magnesium levels. Summary of results Blood pressure decreased with magnesium supplementation of 300 mg.day-1 for 7 days with greater reductions in systolic versus diastolic blood pressure consistently evident. Magnesium supplementation of 300 mg.day-1 for 7 and 14 days increased power during resistance exercise but no changes in aerobic exercise performance were observed. A high habitual dietary magnesium intake attenuated the hypotensive effect derived from magnesium supplementation when compared to those on a low habitual dietary intake. The meta-analysis supported these results. A habitually low dietary magnesium intake was observed in a cohort of clinically diagnosed primary hypertensives. Conclusion These studies show that there is a link between low habitual dietary magnesium intake and elevated blood pressure and that magnesium supplementation appears to be associated with blood pressure. An improvement in resistance exercise performance with magnesium supplementation was also observed. Finally, a transdermal magnesium cream was shown to increase serum magnesium levels and may provide an alternative to oral supplementation.

Low dietary magnesium intake and hypertension

Copyright © 2016 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/Abstract Purpose: Magnesium (Mg) is a key factor in blood pressure regulation. However, only in recent years, magnesium dietary intake has been studied in relation to hypertension, with equivocal conclusions. Further no comparisons have previously been made between the UK general population and primary hypertensives, the UK RNI and the USARDA. Methods: Twenty-five hypertensives (HT) (mean age 63.4 y) and twenty-one normotensives (mean age 46.7 y) were recruited from the same geographical area. Food diaries were completed and analysed to determine average daily Mg intake. Mg intake was compared between the observed group (OB), normotensives (NT) and general population (GP) and both the UK RNI and the USA RDA. Results: Study participants had a significantly lower dietary Mg intake than the UK RNI (p < 0.05) and the US RDA (p < 0.05). Intake for HT males was significantly lower (p < 0.0001) than the external control (general population) and, for HT females, intake was significantly lower than the NT (p = 0.006). The findings also suggest that with ageing there is a reduction in daily dietary Mg intake. Finally, when UK external controls were compared to the USA RDA for both males and females they were found to be around 35% and 30% respectively below the recommended values. Conclusions: Daily Mg intake in hypertensives is lower than the general population, the UK RNI and the USA RDA. Daily magnesium intake reduces with age. These findings suggest that low Mg dietary intake increases the risk of hypertension. Keywords Magnesium, Hypertension, UK RNI, USA RDA, Blood Pressure, Dietary IntakePeer reviewedFinal Published versio

The relationship between the elevation of haemoglobin A1c level, sleep quality and sleep duration in clinically diagnosed pre-diabetic patients in a nationally representative sample

© The Author(s) 2022. This article is distributed under the terms of the Creative Commons Attribution 4.0 License (https://creativecommons.org/licenses/by/4.0/).Background/objectives: Type 2 diabetes mellitus (T2DM) is one of the most common chronic illnesses in the United Kingdom accounting for approximately 15% of deaths per year. Growing evidence suggests that sleep duration and quality contributes towards this. This study aimed to determine whether there was a significant relationship between the elevation of haemoglobin A1c (HbA1c) level, sleep quality (SQ) and sleep duration (SD) in clinically diagnosed pre-diabetic patients.  Subjects/methods: Following referral from a relevant healthcare professional, participants (n = 40) were registered on the National Health Service England, funded Healthier You: National Diabetes Prevention Programme and completed a Pittsburgh Sleep Quality Index questionnaire to evaluate SQ and SD. Results: A Spearman’s correlation showed an association between HbA1c, SQ and SD measures. A simple linear regression showed a significant large positive association (rs = 0.913, p < 0.001) and significant regression (F (1) = 39, p < 0.001) with an R2 of 0.842 between HbA1c level and SQ. Additionally, a significant large negative association (rs = 0.757, p < 0.001) and significant regression was found (F (1) = 39, p < 0.001) with an R2 of 0.570 between HbA1c and SD.  Conclusions: This study suggests a relationship between SQ, SD and the elevation of HbA1c which may contribute towards prevalence of T2DM and may help to increase adherence to diabetes prevention programmes.Peer reviewedFinal Published versio

Changes to Physical Activity, Sitting Time, Eating Behaviours and Barriers to Exercise during the First COVID-19 ‘Lockdown’ in an English Cohort

© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/)This study aimed to determine the effect of the first English national COVID-19 lockdown on physical activity (PA), sitting time, eating behaviours and body mass in an adult cohort. This was further examined to determine whether conforming to recommended guidelines on PA and sedentary behaviour was improved. Based on an online survey (n = 818) incorporating the International Physical Activity Questionnaire Short Form (IPAQ-SF), self-reported body mass change showed that in 32.2% of participants body mass increased, with 39.1% reporting an increase in food intake. Never exercising at the gym or undertaking an exercise class (online or live), increased by 50.8% during lockdown, with 53.5% changing from exercising frequently to never exercising, suggesting a lack of engagement with online and home workouts. However, outdoor running and cycling >2 times/week increased by 38% during lockdown. Walking at least 30 min continuously on >2 occasions/week increased by 70% during lockdown with minimum 10-min walks on 7 days per week increasing by 23%. The lockdown had a negative impact on sitting time (>8 h a day), which increased by 43.6% on weekdays and 121% at weekends. Furthermore, sitting 4 h/day decreased during lockdown (46.5% and 25.6% for weekdays and weekends, respectively). Those citing tiredness or lack of time as a barrier to exercise reduced by 16% and 60%, respectively, from pre-lockdown to during lockdown. More of the sedentary group met the Public Health England PA recommendations, however most participants still did not meet the UK Government guidelines for PA. Improvements in health per additional minutes of physical activity will be proportionately greater in those previously doing 30 min/week, the area where most improvements were found although, conversely sitting time was greatly increased. This study may assist in informing whether future lifestyle changes could improve the health of the population.Peer reviewedFinal Published versio

Heart Rate Recovery Assessed by Cardiopulmonary Exercise Testing in Patients with Cardiovascular Disease: Relationship with Prognosis

© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).Background: The use of exercise testing has expanded in recent decades and there is a wealth of information examining the prognostic significance of exercise variables, such as peak oxygen consumption or ventilatory measures whilst exercising. However, a paucity of research has investigated the use of recovery-derived parameters after exercise cessation. Heart rate recovery (HRR) has been considered a measure of the function of the autonomic nervous system and its dysfunction is associated with cardiovascular risk. Objectives: We aim to provide an overview of the literature surrounding HRR and its prognostic significance in patients with cardiovascular disease undertaking an exercise test. Data Sources: In December 2020, searches of PubMed, Scopus, and ScienceDirect were performed using key search terms and Boolean operators. Study Selection: Articles were manually screened and selected as per the inclusion criteria. Results: Nineteen articles met inclusion criteria and were reviewed. Disagreement exists in methodologies used for measuring and assessing HRR. However, HRR provides prognostic mortality information for use in clinical practice. Conclusions: HRR is a simple, non-invasive measure which independently predicts mortality in patients with heart failure and coronary artery disease; HRR should be routinely incorporated into clinical exercise testing.Peer reviewe

Assessing a commercially available sports drink on exogenous carbohydrate oxidation, fluid delivery and sustained exercise performance

Background: Whilst exogenous carbohydrate oxidation (CHOEXO) is influenced by mono- and disaccharide combinations, debate exists whether such beverages enhance fluid delivery and exercise performance. Therefore, this study aimed to ascertain CHOEXO, fluid delivery and performance times of a commercially available maltodextrin/ fructose beverage in comparison to an isocaloric maltodextrin beverage and placebo. Methods: Fourteen club level cyclists (age: 31.79 ± 10.02 years; height: 1.79 ± 0.06 m; weight: 73.69 ± 9.24 kg; VO2max: 60.38 ± 9.36 mL · kg·-1 min−1) performed three trials involving 2.5 hours continuous exercise at 50% maximum power output (Wmax: 176.71 ± 25.92 W) followed by a 60 km cycling performance test. Throughout each trial, athletes were randomly assigned, in a double-blind manner, either: (1) 1.1 g · min−1 maltodextrin + 0.6 g · min−1 fructose (MD + F), (2) 1.7 g · min−1 of maltodextrin (MD) or (3) flavoured water (P). In addition, the test beverage at 60 minutes contained 5.0 g of deuterium oxide (2H2O) to assess quantification of fluid delivery. Expired air samples were analysed for CHOEXO according to the 13C/12C ratio method using gas chromatography continuous flow isotope ratio mass spectrometry. Results: Peak CHOEXO was significantly greater in the final 30 minutes of submaximal exercise with MD + F and MD compared to P (1.45 ± 0.09 g · min−1, 1.07 ± 0.03 g · min−1and 0.00 ± 0.01 g · min−1 respectively, P < 0.0001), and significantly greater for MD + F compared to MD (P = 0.005). The overall appearance of 2H2O in plasma was significantly greater in both P and MD + F compared to MD (100.27 ± 3.57 ppm, 92.57 ± 2.94 ppm and 78.18 ± 4.07 ppm respectively, P < 0.003). There was no significant difference in fluid delivery between P and MD + F (P = 0.078). Performance times significantly improved with MD + F compared with both MD (by 7 min 22 s ± 1 min 56 s, or 7.2%) and P (by 6 min 35 s ± 2 min 33 s, or 6.5%, P < 0.05) over 60 km. Conclusions: A commercially available maltodextrin-fructose beverage improves CHOEXO and fluid delivery, which may benefit individuals during sustained moderate intensity exercise. The greater CHOEXO observed when consuming a maltodextrin-fructose beverage may support improved performance times

The effect of acute vs chronic magnesium supplementation on exercise and recovery on resistance exercise, blood pressure and total peripheral resistance on normotensive adults

© 2015 Kass and Poeira; licensee BioMed Central. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.Background: Magnesium supplementation has previously shown reductions in blood pressure of up to 12 mmHg. A positive relationship between magnesium supplementation and performance gains in resistance exercise has also been seen. However, no previous studies have investigated loading strategies to optimise response. The aim of this study was to assess the effect of oral magnesium supplementation on resistance exercise and vascular response after intense exercise for an acute and chronic loading strategy on a 2-day repeat protocol. Methods: The study was a randomised, double-blind, cross-over design, placebo controlled 2 day repeat measure protocol (n = 13). Intense exercise (40 km time trial) was followed by bench press at 80% 1RM to exhaustion, with blood pressure and total peripheral resistance (TPR) recorded. 300 mg/d elemental magnesium was supplemented for either a 1 (A) or 4 (Chr) week loading strategy. Food diaries were recorded. Results: Dietary magnesium intake was above the Reference Nutrient Intake (RNI) for all groups. Bench press showed a significant increase of 17.7% (p = 0.031) for A on day 1. On day 2 A showed no decrease in performance whilst Chr showed a 32.1% decrease. On day 2 post-exercise systolic blood pressure (SBP) was significantly lower in both A (p = 0.0.47) and Chr (p = 0.016) groups. Diastolic blood pressure (DBP) showed significant decreases on day 2 solely for A (p = 0.047) with no changes in the Chr. TPR reduced for A on days 1 and 2 (p = 0.031) with Chr showing an increase on day 1 (p = 0.008) and no change on day 2. Conclusion: There was no cumulative effect of Chr supplementation compared to A. A group showed improvement for bench press concurring with previous research which was not seen in Chr. On day 2 A showed a small non-significant increase but not a decrement as expected with Chr showing a decrease. DBP showed reductions in both Chr and A loading, agreeing with previous literature. This is suggestive of a different mechanism for BP reduction than for muscular strength. TPR showed greater reductions with A than Chr, which would not be expected as both interventions had reductions in BP, which is associated with TPR.Peer reviewedFinal Published versio

Effect of Transdermal Magnesium Cream on Serum and Urinary Magnesium Levels in Humans: A Pilot Study

© 2017 Kass et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Background Oral magnesium supplementation is commonly used to support a low magnesium diet. This investigation set out to determine whether magnesium in a cream could be absorbed transdermally in humans to improve magnesium status. Methods and findings In this single blind, parallel designed pilot study, n=25 participants (aged 34.3+/-14.8y, height 171.5+/-11cm, weight 75.9 +/-14 Kg) were randomly assigned to either a 56mg/day magnesium cream or placebo cream group for two weeks. Magnesium serum and 24hour urinary excretion were measured at baseline and at 14 days intervention. Food diaries were recorded for 8 days during this period. Mg test and placebo groups’ serum and urinary Mg did not differ at baseline. After the Mg2+ cream intervention there was a clinically relevant increase in serum magnesium (0.82 to 0.89 mmol/l,p=0.29) that was not seen in the placebo group (0.77 to 0.79 mmol/L), but was only statistically significant (p=0.02)) in a subgroup of non-athletes . Magnesium urinary excretion increased from baseline slightly in the Mg2+ group but with no statistical significance (p=0.48). The Mg2+ group showed an 8.54% increase in serum Mg2+ and a 9.1% increase in urinary Mg2+ while these figures for the placebo group were smaller, i.e. +2.6% for serum Mg2+ and -32% for urinary Mg2+. In the placebo group, both serum and urine concentrations showed no statistically significant change after the application of the placebo cream. Conclusion No previous studies have looked at transdermal absorbency of Mg2+ in human subjects. In this pilot study, transdermal delivery of 56 mg Mg/day (a low dose compared with commercial transdermal Mg2+ products available) showed a larger percentage rise in both serum and urinary markers from pre to post intervention compared with subjects using the placebo cream, but statistical significance was achieved only for serum Mg2+ in a subgroup of non-athletes. Future studies should look at higher dosage of magnesium cream for longer durations.Peer reviewe

A pilot study on the effects of magnesium supplementation with high and low habitual dietary magnesium intake on resting and recovery from aerobic and resistance exercise and systolic blood pressure

The effects of magnesium supplementation on blood pressure (BP) have been studied for over 25 years and results have been inconsistent. Blood pressure reductions in randomized studies have varied from 12 mmHg reductions to no reduction. The objective of this pilot intervention was to investigate the effect of magnesium supplementation on systolic blood pressure whilst resting and during recovery from aerobic and resistance exercise and on performance. A further objective was to see whether the effect of a high vs low habitual dietary magnesium intake affected these results. Sixteen male volunteers were randomly assigned to either a 300mg/d magnesium oxide supplementation (MO) or a control group (CG) for 14 days. Resting blood pressure (BP) and heart rate (HR) were measured before subjects performed a maximal 30 minute cycle, immediately followed by three x 5 second isometric bench press, both at baseline and after the intervention. Blood pressure and heart rate were recorded immediately post exercise and after five minutes recovery. A 3 day food diary was recorded for all subjects to measure dietary magnesium intake. At the end of the intervention, the supplemented group, had a reduction in mean resting systolic BP by 8.9 mmHg (115.125 ± 9.46 mmHg, P=0.01) and post exercise by 13 mmHg (122.625 ± 9.88 mmHg, P=0.01). Recovery BP was 11.9 mmHg lower in the intervention group compared to control (P=0.006) and HR decreased by 7 beats per minute in the experimental group (69.0 ± 11.6 bpm, P=0.02). Performance indicators did not change within and between the groups. Habitual dietary magnesium intake affected both resting and post exercise systolic BP and the subsequent effect of the magnesium supplementation. These results have an implication in a health setting and for health and exercise but not performance.Peer reviewedSubmitted Versio

Adolescent to Adulthood : Nutrition for health and Well Being

Non peer reviewe