Metabolic, Anthropometric and Blood Pressure Effects of Adding Two Kiwifruit or Bottled Water into the Diets of People with Pre-Diabetes: A Randomised, Parallel Group, Intervention Study

People with pre-diabetes may be reluctant to add fruit to their diets due to concerns around sugars. Our objective was to measure outcomes associated with potential adverse effects of ingesting fruit sugars while assessing metabolic benefits from eating nutrient-rich kiwifruit. Thirty-four people with pre-diabetes were randomized to receive two kiwifruit or 250 mL bottled water per day for 12-weeks; two people withdrew. The primary outcomes were between-group differences for glycated haemoglobin (HbA1c) and plasma vitamin C concentration. Secondary outcomes included anthropometry, blood pressure, lipids, uric acid, glycaemic-, inflammatory- and oxidative-markers. Mean (95% confidence interval) vitamin C intake and plasma concentration increased by 170 (141, 200) mg/d (P<0.001) and 11 (5, 17) µM (P = 0.001), respectively, in the kiwifruit compared with the control group. There was no between-group difference for HbA1c or for anthropometric, blood pressure or metabolic markers except for Trolox equivalent antioxidant capacity (TEAC) assay, for which there was a mean decrease of 27 (3, 51) mM (P = 0.027) in the plasma of the kiwifruit compared with the control group. The inclusion of two kiwifruit per day into the diets of people with pre-diabetes raised vitamin C intake and status without causing metabolic disturbance due to the sugars contained in the fruit. The reason behind a reduction in TEAC in the kiwifruit group despite an increase in plasma vitamin C is unclear. For any beneficial effect on HbA1c to become evident, it may require a larger sample and a longer intervention.