Impact of Grape Powder Consumption on Eye Health and Glycemic Status in Singapore Older Adults

Impact of Regular Consumption of Grape on Eye Health and Regulation of Advanced Glycation End-products in Singapore Older Adults

The purpose of this study is to understand the impacts of regular consumption of freeze-dried table grape powder on eye health and regulation of advanced glycation end products in Singapore older adults. The investigators hypothesize that regular consumption of freeze-dried table grape powder will promote improvements in eye health and lower levels of advanced glycation end products when compared to the placebo group.

Study Overview

• Status: Not yet recruiting
• Conditions: Aging; Macula; Degeneration; Advanced Glycation End Products
• Intervention / Treatment: Dietary supplement: Freeze-dried table grape powder; Dietary supplement: Placebo grape powder

Detailed Description

The study will be a 16-week, double-blind, randomized, placebo-controlled trial using a parallel study design. 46 adults (aged 60 - 85) will be recruited and randomly assigned to the intervention or placebo group to investigate whether regular consumption of freeze-dried table grape powder (46g/d) can improve eye health parameters, blood/skin AGE and glycemic status, and reduce inflammation and oxidative stress. This study will consist of 1 screening visit and 5 study visits with 4-week intervals.

• Study Type: Interventional
• Enrollment (Estimated): 46
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Marcus Ting; Phone Number: 97851245; Email: marcusting@u.nus.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

1. Male and female participants, aged between 60 and 85 years old inclusive
2. English-literate and able to give informed consent in English

Exclusion Criteria:

1. Smokers
2. Allergy to grapes or food dyes/additives, or had serious food allergies in the past
3. Known eye diseases (macular degeneration, cataracts, retinopathy or glaucoma), blindness in at least one eye or have had eye surgery
4. Unable to view bright lights or flashing lights
5. Has Type 1 or 2 diabetes, uremia, cardiovascular disease, abnormal kidney and liver function
6. Taking eye medication and/or dietary supplements for the eyes for the past 3 month
7. Taking supplements containing carotenoids (e.g. Vitamin A, lutein, zeaxanthin) for past 3 months
8. Currently on a specialised diet (e.g. vegetarian, vegan, weight loss diet, low fat diet
9. Consumes more than 2 alcoholic drinks per day i.e. one drink is defined as either 150ml of wine,340ml of beer/cider or 45ml of distilled spirit
10. Significant change in weight (≥ 3 kg body weight) in the past 3 months
11. Significant exercise pattern over the past 3 months defined as high-intensity exercise of more than 3 hours per week
12. Currently on anti-hypertensive, cholesterol-lowering or psychoactive drugs
13. Scored ≤ 7 on the abbreviated mental test
14. Poor peripheral venous access based on past experiences with blood draw
15. Participating in another clinical study

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Freeze-dried table grape powder; Subjects in this group will be given pouches, each containing 46 g of freeze-dried table grape powder, with an instruction sheet on how to prepare the powder into a drink for consumption.They will consume one pouch a day.	Dietary supplement: Freeze-dried table grape powder; Consumption of grape powder as part of daily diet
Placebo Comparator: Placebo table grape powder; Subjects in this group will be given pouches, each containing 46 g of placebo grape powder, with an instruction sheet on how to prepare the powder into a drink for consumption.They will consume one pouch a day.	Dietary supplement: Placebo grape powder; Consumption of placebo grape powder as part of daily diet

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Macular pigment optical density	A measurement of macular pigment of the eye using a heterochromatic flicker photometry device. The measurements are in arbitrary units.	Week 0, Week 4, Week 8, Week 12, Week 16
Visual acuity	Participants will read out letters on a ETDRS LogMAR chart at a fixed distance where letters becomes smaller as it goes down the chart. Tests results will be recorded in number of letters read, where the more letters the better the outcome.	Week 0, Week 4, Week 8, Week 12, Week 16
Photostress recovery time	An ophthalmoscope will be used to shine a light into the participants eye for 10 seconds, and participants will be required to read letters off a chart the moment their vision returns to normal. The faster the recovery time, the better the outcome. Units will be in seconds	Week 0, Week 4, Week 8, Week 12, Week 16
Visual function questionnaire 25	A questionnaire to for participants to self-evaluate their perception of their current eye health based on general vision, ocular pain, near activities, distance activities, vision specific functions, driving, color vision and peripheral vision. The best possible score is 100 and worst possible score is 0.	Week 0, Week 4, Week 8, Week 12, Week 16
Skin advanced glycation end products levels	Measurement of skin advanced glycation end products level using a skin autofluorescence device, where participants wlll be instructed to place their forearm over the device and a light will be shone and a reading can be captured by detecting fluorescence. The results will be presented as arbitrary units.	Week 0, Week 4, Week 8, Week 12, Week 16
Dietary advanced glycation end products level	Participants will be instructed to record down 3-day food records, from Thursday to Saturday, before each clinical visit. This will be used to estimate their advanced glycation end products intake from food by referring to existing nutrient databases. Units will be based on a common advanced glycation end product measured, carboxymethyllysine (CML), thus the unit will be mg CML/ kg food	Week 0, Week 4, Week 8, Week 12, Week 16
Blood advanced glycation end products levels	Participants will have their blood drawn by medical professionals at the Occupational Health Clinic. The blood will be processed and stored. Measurements will be done using ultra-performance liquid chromatography coupled with mass spectrometry techniques to determine the levels of advanced glycation end products. Units will be in μg/mL.	Week 0, Week 8 and Week 16
Contrast sensitivity	Participants will read out letters on a ETDRS LogMAR chart at a fixed distance, where the letters differs in lightness to test participants' sensitivity to contrast. Tests results will be recorded in number of letters read, where the more letters the better the outcome.	Week 0, Week 4, Week 8, Week 12, Week 16

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Concentration of tumour necrosis factor-α	The blood obtained from the participants will be processed for storage. Tumor necrosis factor-α results will be presented in ng/L according to the commercially available enzyme-linked immunosorbent assay kits.	Week 0, Week 8, Week 16
Concentration of interleukin-6	The blood obtained from the participants will be processed for storage. Interleukin-6 results will be presented in ng/L according to the commercially available enzyme-linked immunosorbent assay kits.	Week 0, Week 8, Week 16
Concentration of high-sensitivity C-reactive protein	The blood obtained from the participants will be processed for storage. Analyses of inflammation markers include tumor necrosis factor-α, interleukin-6. high sensitivity C-reactive protein. Tumor necrosis factor-α and interleukin-6 results will be presented in ng/L according to the commercially available enzyme-linked immunosorbent assay kits. High-sensitivity C-reactive protein results will be obtained and presented in mg/L by commercial lab testing.	Week 0, Week 8, Week 16
Concentration of fasting blood glucose	Fasting blood glucose will be measured using commercial lab testing using participants' blood, units will be in mmol/L.	Week 0, Week 8, Week 16
Concentration of malondialdehyde	The blood obtained from the participants will be processed for storage. Analyses of malondialdehyde using commercially available enzyme-linked immunosorbent assay kits. Units for malondialdehyde will be in ng/L according to assay kit instructions.	Week 0, Week 8, Week 16
Concentration of 8-isoprostaglandin-F2α	The blood obtained from the participants will be processed for storage. Analyses of 8-isoprostaglandin-F2α using commercially available enzyme-linked immunosorbent assay kits. Units for 8-isoprostaglandin-F2α will be in µmol/L according to assay kit instructions.	Week 0, Week 8, Week 16
Skin carotenoid status	Measured using a commercially available device that measured carotenoids using Raman spectroscopy. Results are in arbitrary units.	Week 0, Week 4, Week 8, Week 12, Week 16;
Concentration of insulin	Fasting blood insulin will be measured using commercial lab testing using participants' blood, units in μU/L.	Week 0, Week 8, Week 16
Percentage of glycated hemoglobin	Glycated hemoglobin will be measured using commercial lab testing from participant's blood, units in percent.	Week 0, Week 8, Week 16

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Measurement of height	Height will be measured using height-weight scale and units will be in cm.	Week 0, Week 4, Week 8, Week 12, Week 16
Measurement of blood pressure	A blood pressure monitoring device available commercially will be used be to measure their systolic nad diastolic blood pressure.	Week 0, Week 4, Week 8, Week 12, Week 16
Measurement of weight	Weight will be measured using height-weight scale and units will be in kg.	Week 0, Week 4, Week 8, Week 12, Week 16
Measurement of waist circumference	Waist circumference will be measured using a measuring tape by a trained personnel, units in cm.	Week 0, Week 4, Week 8, Week 12, Week 16

Collaborators and Investigators

• Sponsor: National University of Singapore
• Collaborators: California Table Grape Commission
• Investigators: Principal Investigator: Jung Eun Kim, Ph.D., R.D., National University of Singapore

Publications and helpful links

General Publications

• Hu W, Zheng R, Feng Y, Tan D, Chan Chung-Tsing G, Su X, Kim JE. Impacts of regular consumption of grapes on macular pigment accumulation in Singapore older adults: a randomized controlled trial. Food Funct. 2023 Sep 19;14(18):8321-8330. doi: 10.1039/d3fo02105j.

Study record dates

Study Major Dates

• Study Start (Estimated): May 1, 2024
• Primary Completion (Estimated): August 1, 2025
• Study Completion (Estimated): August 1, 2025

Study Registration Dates

• First Submitted: March 14, 2024
• First Submitted That Met QC Criteria: April 4, 2024
• First Posted (Actual): April 5, 2024

Study Record Updates

• Last Update Posted (Actual): April 5, 2024
• Last Update Submitted That Met QC Criteria: April 4, 2024
• Last Verified: April 1, 2024

More Information

Terms related to this study

• Keywords: Oxidative stress; Inflammation; Older adults; Vitis vinifera; Eye health; Glycemic status
• Other Study ID Numbers: S25

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: Electronic copies of the data with identifiable participant information will be kept on NUS OneDrive with access limited only Dr Kim Jung Eun and her research staff. All data will be de-identified prior to statistical analyses.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No