Poster Presentation Nutrition Society of Australia 50th Annual Scientific Meeting 2026

Acute cardiovascular effects of an L-Theanine and L-Glycine beverage in postmenopausal women at rest: Protocol for a randomised controlled trial (146791)

Harshini Meegaswatte 1 2 3 , Kathryn E Speer 1 4 5 , Ekavi N Georgousopoulou 1 , Andrew J McKune 2 3 6 , Stuart Semple 2 5 7 , Nenad Naumovski 1 2 3 8
  1. Discipline of Nutrition and Dietetics, Faculty of Health, University of Canberra, Canberra, Bruce, ACT, Australia
  2. University of Canberra Research Institute for Sport and Exercise (UCRISE), University of Canberra, Bruce, ACT, Australia
  3. Functional Foods and Nutrition Research (FFNR) Laboratory, Food, Chemical and Biotechnology Cluster, Singapore Institute of Technology, Singapore, 828608
  4. School of Nursing & Midwifery, Faculty of Health, University of Canberra, Canberra, Bruce, ACT, Australia
  5. Discipline of Sport and Exercise Science, Faculty of Health, University of Canberra, Bruce, ACT, Australia
  6. Discipline of Biokinetics, Exercise and Leisure Sciences, School of Health Science, University of KwaZulu-Natal, Durban 4041, South Africa
  7. Health Research Institute, University of Canberra, Bruce, ACT, Australia
  8. Food, Chemical and Biotechnology Cluster, Singapore Institute of Technology, Singapore, 828608

Cardiovascular diseases (CVD) are the leading cause of death worldwide and their prevalence continues to increase due to population growth and population aging (1). The proportion of the global population aged ≥60 years is projected to increase from 12% to 22% between 2015 to 2050, alongside a near doubling of CVD incidence among women aged ≥55 years over the past three decades (2; 3). Postmenopausal women experience an increased risk of CVD due to hormonal changes, central adiposity, insulin resistance, dyslipidemia, vascular dysfunction, and oxidative stress (4; 5; 6). Functional foods and beverages are developed with additional ingredients that may provide health benefits beyond their nutritional value (7). The amino acids, L-Glycine (L-Gly) and L-Theanine (L-The) have been reported to possess antioxidant and anti-inflammatory properties and have been identified as potential nutraceuticals for the management of metabolic diseases (8). However, their combined effects on cardiovascular physiology in postmenopausal women remain unexplored. This trial aims to investigate the acute effects of a beverage containing L-The (200 mg) and L-Gly (5000 mg) (The-Gly) on resting cardiovascular responses, including heart rate (HR), heart rate variability (HRV), blood pressure (BP), skin microvascular function, in postmenopausal women. The study was approved by the University of Canberra Human Research Ethics Committee (Approval No. 89428) and prospectively registered with the Australian New Zealand Clinical Trials Registry (ACTRN12625001335482). Thirty otherwise healthy naturally postmenopausal women aged ≥ 45 years and at least 12 months since their final menstruation will be recruited. Women who experienced menopause due to hysterectomy, medical conditions, or medical treatments, as well as those currently receiving menopausal hormone therapy, will be excluded. Participants will be randomised (1:1) to receive either the The-Gly active beverage or a placebo in a double-blind, parallel-group trial. Baseline assessments will include cardiometabolic risk biomarkers (fasting glucose, HbA1c, total cholesterol, triglycerides, and high-density lipoprotein cholesterol  measured using the SimplexTAS 101), cardiorespiratory fitness (maximal aerobic capacity), anthropometry (standing height, body weight, waist circumference, hip circumference), physical function (grip strength, gait speed, chair-rise ability) and measures of depression and anxiety. The primary outcomes, including HR, HRV [with RMSSD, primary metric], BP), and skin microvascular function (assessed using forearm post-occlusive reactive hyperaemia response measured via laser Doppler flowmetry), will be assessed with  participants resting in a  supine position at baseline and at 60 and 120 minutes following beverage consumption. Data will be analysed using general linear mixed models. This trial will provide novel insights into the acute cardiovascular effects of a combined L-Theanine and L-Glycine beverage in postmenopausal women. The findings may provide a foundation for the development of functional foods and nutraceuticals aimed at mitigating menopause-related cardiovascular risk and improving cardiometabolic health in postmenopausal women.

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