Flavonoids are compounds that have been proven to have a beneficial effect on health, such as reducing the risk of developing cardiovascular disease and, in some cases, cancer. Citrus juices have a high flavonoid content. However, the absorption of flavonoids into the body is limited. This study will investigate whether being physically active improves the absorption of flavonoids.

Endurance trained athletes will be invited to participate. Following screening procedures (a. Health Screening Questionnaire; b. height and weight measurement for calculation of Body Mass Index; c. maximal oxygen consumption (VO2max) uptake test, eligible participants will undertake two experimental tests; one during a period of normal training, the other immediately following 1 week of detraining.

In the morning of the experimental trial participants will consume 500 mL of orange juice. Blood samples and urinary fractions will be collected prior (base line) to and for 24 hours after orange juice consumption. Participants will be asked to follow a special polyphenol-free diet and record weighed dietary intake for 2 days preceding each trial and during the day of the experimental trial.

The study aims to:

1. Determine the effects of training status of endurance athletes on bioavailability of flavanones in endurance trained individuals
2. Determine whether changes in bioavailability of flavanones are related to changes in biomarkers of inflammation, oxidative stress, plasma lipids and insulin sensitivity.

Inclusion Criteria:

• trained regularly for at least 4 years and typically perform at least 5 hours of endurance training per week (distance runners, triathletes, cyclists)
• healthy
• normotensive
• non-smokers
• not taking any drug therapies
• VO2 max >50 ml/kg body mass

Exclusion Criteria:

• history of gastrointestinal disease
• vegetarian
• unstable food habits
• VO2 max < 50 ml/kg body mass