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    Effect of beetroot pomace consumption on acute blood pressure and postprandial blood glucose responses on healthy adults : a thesis presented in the partial fulfilment of the requirements for the degree of Master of Science in Nutrition and Dietetics, Massey University, Albany, New Zealand
    (Massey University, 2023) Gorbani, Elnaz
    Background: Nitrate-rich beetroot juice (BRJ) supplementation has been shown to improve blood pressure (BP) levels in younger and older adults via increased nitric oxide (NO) production leading to dilation of blood vessels. Similarly, to some extent a reduction of blood glucose (BG) levels through several different mechanisms. However, limited research exists on the by-product of beetroot juice production, beetroot pomace (BRPOM), and its role in controlling BP and BG levels. Objective: To investigate and compare the changes in BP and BG levels in a 3 h period following the ingestion of BRPOM, BRJ and placebo as part of an oral glucose tolerance test (OGTT). Methods: Following an overnight fast, twelve healthy adults consumed either BRPOM (600 mg nitrate, 10 g fibre, 75 g carbohydrate), BRJ (600 mg nitrate, <1 g fibre, 75 g carbohydrate), or placebo (0 mg nitrate, <1 g fibre, 75 g carbohydrate) 15 minutes prior to the OGTT, separated by 1-week washout periods, in a single-blind, crossover design, pilot study. Blood pressure and BG levels were measured at baseline, then every 15 minutes for BG and every hour for BP during a 3 h OGTT. Results: No significant changes in SBP for BRJ (-2.3 ± 5.56 mmHg, p = 0.174), BRPOM (-3 ± 13.4 mmHg, p = 0.456), or PLA (5.2 ± 11.3 mmHg, p = 0.142) treatment group after 3 h. However, there was a trend towards significance in the differences between the three groups (p = 0.075, η²ₚ = 0.404). Clinically meaningful reductions in SBP were observed for BRJ (-2.3 ± 5.56 mmHg) and BRPOM (-3 ± 13.4 mmHg). There were no differences (p = 0.739, η²ₚ = 0.059) in mean glucose incremental area under the curve (iAUC) between BRJ, BRPOM and PLA (232.8 ± 61.9, 242 ± 54.7 and 252.4 ± 60.6 mmol/L/min, respectively). There were no differences between BRJ, BRPOM and PLA in time to peak (p = 0.269, η²ₚ = 0.313), peak glucose levels (p = 0.241, η²ₚ = 0.247), 2 h glucose levels (p = 0.565, η²ₚ = 0.150), 3 h glucose levels (p = 0.395, η²ₚ = 0.233) and percentage increment of postprandial BG (p = 0.783, η²ₚ = 0.048). Conclusion: This pilot study with a small sample size showed a large effect size and clinically meaningful attenuations for acute SBP changes following the consumption of beetroot pomace. Further investigations would be needed to explore the applicability of these findings to hypertensive individuals. However, its impact on acute BG levels remains non-significant, possibly influenced by the small sample size and participants’ baseline normoglycaemic levels. Further research is needed to explore potential effects in a hyperglycaemic population.
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    Breakdown of rice and wheat-based foods during gastric digestion and its implications on glycemic response : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand
    (Massey University, 2022) Nadia, Joanna
    The composition and structure of starch-based foods determine their breakdown behavior in the digestive tract and consequently their glycemic response. The glycemic response of starch-based foods is known to be influenced by their gastric emptying rate. However, the role of gastric digestion in regulating this process has not been well-understood, especially on how food breakdown behavior in the stomach may be related to the glycemic response. In this project, the link between food structure, food breakdown during gastric digestion, gastric emptying, and glycemic response was investigated in vivo using a growing pig model. Durum wheat- and white rice-based foods of varying physical structures (semolina porridge, rice- and wheat couscous, rice grain, rice noodle and wheat noodle/pasta) were studied. It was found that the foods with smaller-sized particles (semolina porridge and couscous products) had faster gastric breakdown rate and gastric emptying rate, resulting in higher glycemic impact (maximum change from the baseline and the overall impact) compared to the foods with larger-sized particles (rice grain and noodle products). The faster gastric breakdown rate of the smaller-sized foods was related to their acidification rate in the stomach, which caused their dilution or dissolution by gastric secretions. For larger-sized foods, their gastric breakdown rate and gastric acidification rate were slower, which extended their contact time with salivary amylase in the proximal stomach. To elucidate further the role of the proximal and distal phases of gastric digestion in solid food breakdown, a static in vitro digestion was conducted with the same food products. In the smaller-sized foods, both the proximal and distal phases led to their dissolution. Meanwhile, for the larger-sized foods, the extended contact time with α-amylase in the proximal phase contributed to the leaching of starch particles from the food, which was important to aid their breakdown during gastric digestion. The distal phase contributed to the softening of the larger-sized foods, but its softening effect was limited. The knowledge on the contributions of the phases of gastric digestion and the identified link between food structure, gastric digestion, and glycemic response in this thesis may be useful for structuring starch-based foods with controlled glycemic properties. 
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    Kiwifruit and guar gum modulation of postprandial blood glucose and its cognitive effects : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Psychology at Massey University
    (Massey University, 2015) Edwards, `Haley
    Glucose is the main source of energy for the brain, and blood glucose levels have been shown to have a significant impact on cognitive performance. This thesis research examined the effects of kiwifruit and guar gum (a soluble fiber) on the postprandial blood glucose response, and to what extent glucose manipulation can influence cognitive performance. Twenty healthy participants took part in a within subjects trial, with each individual consuming one of four breakfast diets per week (Weet-Bix, Weet-Bix + Kiwifruit, Weet-Bix + Guar Gum, and Weet- Bix + Kiwifruit + Guar gum). Each breakfast was separated by at least a 1-week washout period. It has been shown that kiwifruit and its interaction with guar gum decreases blood glucose peaks during the postprandial phase, and maintains a glucose level above fasting baseline measures over a 3-hour time period. In the present study there were no main effects of Breakfast Type across the cognitive tasks, or for interactions between Breakfast Type and Testing Time. However, there was a significant effect for time for each task, collapsed across each breakfast. (Time refers to the three points the cognitive tests were administered, one pre-breakfast, and two post-breakfast at 90 and 180 mins). Trends in the blood glucose response data indicated that when blood glucose levels were controlled and maintained (by the kiwifruit and guar gum), performance on some cognitive tasks improved and was largely sustained across the 3-hour time period, although the effects of practice could not be ruled out.