Impact of training status on bioavailability of flavanones

Plain English summary of protocol

Background and study aims
Flavonoids are compounds that have been proven to be beneficial to health. They are found in virtually all plants and are responsible for many of the different colours of our fruits and vegetables. Citrus juices, for example, have a high flavonoid content. They are antioxidants, mopping up reactive oxygen-containing molecules that would otherwise damage body cells. They are known to help reduce the risk of developing cardiovascular disease (for example, heart attack and stroke) and, in some cases, cancer. However, the uptake (absorption) of flavonoids from foods into the body is limited. Here, we want to see whether being physically active improves the absorption of flavonoids into the body.

Who can participate?
Distance runners, triathletes and cyclists, 18 years old or older, training regularly for at least 4 years and typically doing at least 5 hours of endurance training per week. All participants must be healthy , with normal blood pressure, non-smoking, and not taking any drug therapies. Screening of participants is performed with Health Screening Questionnaire, Physical Activity Readiness Questionnaire and VO2 max test. Only those with VO2 max >50 ml/kg body mass are included.

What does the study involve?
All participants do 2 experimental tests: one during a period of normal training and the other immediately following 1 week of not training. On the day of each test, the participants arrive at around 8.30am. A sample of blood is taken after which they are given 500 ml of orange juice and a polyphenol-free breakfast. Further blood samples are obtained at 3, 4, 5, 6, 7, 8 hours after drinking the juice. A total of 90 ml of blood is taken over the course of the day. At four hours after the first blood sample collection, the participants are given a white roll and butter. At the end of the test, they are given a polyphenol-free dinner. Participants are allowed to leave after dinner, told to avoid polyphenol containing foods during the rest of the day and record all food and drink consumed. They are asked to come back the next morning in a fasted state (that is, not having eaten or drunk anything other than clear fluids). One last blood sample is taken. Participants are provided with breakfast. They are also asked to collect urine into plastic bottles at between 0– 6 hours, 6 – 11 hours and then 11 – 24 hours after the drinking the juice. Other than specific tasks described above, for 2 days before each experimental test, participants are asked to follow a polyphenol-free diet. A list with polyphenol-free food is provided below. Participants are also asked to record their food intake throughout these 2 days before the first experimental test and replicate this food intake before the second one. During the 24 h prior to the experimental test participants are asked to collect urine, at between 0– 6 hours, 6 – 11 hours and then 11 – 24 hours leading up to the tests. They are asked to fast for 12 hours beforehand too. From the day following the first experimental test participants are asked to not do any training until the second experimental test one week later.
Foods prohibited during the polyphenol free diet
1. Tea, coffee, drinking chocolate, alcohol (especially red wine, beer, apple cider), fruit juice
2. Fruits and vegetables
3. Chocolate and chocolate products
4. Cereals/ wholemeal bread/ grains
5. Spices (such as curry) and herbs
Foods allowed during the polyphenol free diet
1. White bread
2. Butter, vegetable oil (but avoid olive oil)
3. Pasta, rice
4. Meat, eggs, fish
5. Peeled potatoes (mash, crisps, French fries)
6. Digestive biscuits (not whole meal or chocolate)
7. Milk and milk products (plain yoghurts, cheese)

What are the possible benefits and risks of participating?
After the completion of the study, participants were paid £80. Since VO2max was measured participants received information on their cardiovascular fitness level.

Where is the study run from?
The Metabolic suite of the Human Nutrition department of the University of Glasgow which is based in the New Lister building of the Royal Infirmary in Glasgow (UK)

When is study starting and how long is it expected to run for?
May 2014 to March 2015.

Who is funding the study?
University of Glasgow (UK)

Who is the main contact?
Dr Thelma Polyviou
thelma.polyviou@glasgow.ac.uk

Contact information

Study information

Eligibility

Locations

Countries of recruitment

• Scotland
• United Kingdom

Study participating centre

Sponsor information

University of Glasgow
University/education

Wolfson Medical School Building
University Avenue
Glasgow
G12 8QQ
Scotland
United Kingdom

Email	mvls-enquiries@glasgow.ac.uk
"ROR"	https://ror.org/00vtgdb53

Funders

Funder type

University/education

Results and Publications

Study outputs

Editorial Notes

23/07/2019: The following changes were made to the trial record:
1. ClinicalTrials.gov number added.
2. Publication reference added.
08/06/2017: No publications found in PubMed, verifying study status with principal investigator