SunGold Kiwifruit Supplementation of Individuals with Prediabetes Alters Gut Microbiota and Improves Vitamin C Status, Anthropometric and Clinical Markers.

Nutrients. 2018;10(7)
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Increased plasma glucose levels are linked with increased oxidative stress. An increase in the uptake of antioxidants such as vitamin C through diet has been demonstrated by several studies as contributing to the maintenance of normal glucose levels and reducing the risk factors for Type 2 diabetes. The aim of this study was to investigate the vitamin C status, anthropometric measurements and faecal microbiota of an individual on consumption of high vitamin C kiwi fruit for a period of 12 weeks. Baseline measures were compared at the end of 12 weeks resulting in significant increase in plasma vitamin C status (14 µmol/L, p < 0.001). Significant reduction in blood pressure measurement (4 mmHg, p = 0.029), reduction in waist- to- hip ratio and waist- circumference, decrease in blood glucose marker HbA1c (1 mmol/mol, p = 0.005) and increase in fasting glucose (0.1 mmol/L, p = 0.046) were also observed at the end of twelve weeks. Faecal microbiota composition showed an increase in the abundance of uncharacterised bacterial family. The authors concluded that these result were not sufficiently significant to draw conclusions and further studies with larger sample sizes are required to confirm the outcomes of this study.

Abstract

Kiwifruit are a nutrient dense food and an excellent source of vitamin C. Supplementation of the diet with kiwifruit enhances plasma vitamin C status and epidemiological studies have shown an association between vitamin C status and reduced insulin resistance and improved blood glucose control. In vitro experiments suggest that eating kiwifruit might induce changes to microbiota composition and function; however, human studies to confirm these findings are lacking. The aim of this study was to investigate the effect of consuming two SunGold kiwifruit per day over 12 weeks on vitamin C status, clinical and anthropometric measures and faecal microbiota composition in people with prediabetes. This pilot intervention trial compared baseline measurements with those following the intervention. Participants completed a physical activity questionnaire and a three-day estimated food diary at baseline and on completion of the trial. Venous blood samples were collected at each study visit (baseline, 6, 12 weeks) for determination of glycaemic indices, plasma vitamin C concentrations, hormones, lipid profiles and high-sensitivity C-reactive protein. Participants provided a faecal sample at each study visit. DNA was extracted from the faecal samples and a region of the 16S ribosomal RNA gene was amplified and sequenced to determine faecal microbiota composition. When week 12 measures were compared to baseline, results showed a significant increase in plasma vitamin C (14 µmol/L, p < 0.001). There was a significant reduction in both diastolic (4 mmHg, p = 0.029) and systolic (6 mmHg, p = 0.003) blood pressure and a significant reduction in waist circumference (3.1 cm, p = 0.001) and waist-to-hip ratio (0.01, p = 0.032). Results also showed a decrease in HbA1c (1 mmol/mol, p = 0.005) and an increase in fasting glucose (0.1 mmol/L, p = 0.046), however, these changes were small and were not clinically significant. Analysis of faecal microbiota composition showed an increase in the relative abundance of as yet uncultivated and therefore uncharacterised members of the bacterial family Coriobacteriaceae. Novel bacteriological investigations of Coriobacteriaceae are required to explain their functional relationship to kiwifruit polysaccharides and polyphenols.

Lifestyle medicine

Patient Centred Factors : Triggers/Vitamin C
Environmental Inputs : Diet ; Nutrients
Personal Lifestyle Factors : Nutrition ; Environment
Functional Laboratory Testing : Blood ; Stool
Bioactive Substances : Vitamin C

Methodological quality

Allocation concealment : Not applicable
Publication Type : Clinical Trial ; Journal Article

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