COVID-19 related inability to complete study

This study aims to find out if consuming a single dose of blueberries, rich in anthocyanins, within an energy dense meal, improves blood vessel function and biomarkers of heart health. The study specifically aims to confirm if differences in how individuals process the bioactive compounds in blueberries, called anthocyanins, has an influence on heart health. The investigators will assess the effects of eating one portion of blueberries on vascular health over a 48hour period, and will track the breakdown compounds within blood and urine, to see if health effects are related to metabolism.

The primary aim of this cross-over designed, placebo controlled, acute dietary intervention study, is to prospectively recruit participants on the basis of anthocyanin metabolism profiles (based on profiles confirmed in our previous studies) following a 'blueberry challenge'. Acute cardio and metabolic function responses will be assessed (by metaboliser profile), following an energy dense test meal with/without the addition of blueberries.

Participants will be healthy, but overweight and obese (BMI inclusion: ≥ 25kg/m2) men and women (aged 50 y to 80 y), who will initially undertake a 'blueberry challenge' by consuming a single dose of freeze dried blueberries. Anthocyanin metaboliser type will be profiled from the analysis of metabolites within urine, collected for 48h following the 'challenge'.

A total of 70 participants will complete the intervention (n=35 FAST and n=35 SLOW metabolisers) which consists of two, test meal periods (separated by at least 7d and allocated in random order); 1) energy dense test meal plus freeze dried blueberries, 2) energy dense test meal plus an isocaloric matched placebo material. Urine samples and ambulatory blood pressure measures will be collected for 24h prior to, and then over the 48h period which follows the test meal intake. Further assessment of vascular and metabolic function will be made at pre-defined times over the 48h postprandial period. Dietary restrictions to abstain from blueberries and reduce the anthocyanin intake level, will be applied for 5d before each test meal intake. In addition, all food and drink will be provided for a 4d period (2d before and during the 48h following the energy dense test meal) to further control the intake of flavonoids and to standardise the influence of background diet on metabolism profile.

Inclusion Criteria:

• BMI >= 25 kg/m2
• Adults aged 50 - 80 years old
• Successful biochemical, haematological, and urinalysis assessment at screening

Exclusion Criteria:

• Current smokers, or ex-smokers ceasing < 6 months ago
• existing or significant past medical history of vascular disease or medical conditions likely to affect the study measures
• Fructose or lactose intolerant subjects or known allergies to intervention treatments
• Those unprepared to adhere to dietary instructions
• Parallel participation in another research project involving dietary intervention and/or sampling of biological fluids/material
• Those on therapeutic diets or having experienced substantial weight loss within 2 months of screening.
• Those taking flavonoid, nitrate / nitrite containing or fish oil containing supplements (and unwilling to cease intake during, and 1 month preceding the trial) or unwilling to maintain existing intake of other supplements.
• Prescribed hypoglycaemic, anti-hypertensive, vasodilator or hormone replacement therapy (HRT) medication.
• Unsatisfactory biochemical, haematological or urinary results or measurements considered to be counter indicative for the study
• Undiagnosed hypertension (elicited at screening; i.e. ≥ 180 / 110mmHg) at a level requiring immediate referral back to general practitioner for follow-up

The randomised allocation of treatment order for each participant will be performed by an independent researcher with experience in statistical randomisation. The Principle Investigator will receive notification of the treatment coding order for each subject (in a tamper-evident sealed envelope) which will be prepared by the independent researcher trained in statistics. The coding of the treatment randomisation will only be known to this researcher; and will only be broken at the analysis stage of the study unless a serious adverse event occurs. As the intervention material is a powdered food product, or placebo material, it is considered unlikely that this eventuality may occur.

During the analysis stage, a blind review of data quality and outlier data will be performed prior to unblinding. Researchers analysing the raw data will remain blind and the data will be locked prior to unblinding of the statistician (which will only occur after the completion of the statistical analysis).