Human urinary metabolic profiling showed to be very successful to elucidate biomarkers linked to geographic origin and specific food consumption patterns (Holmes and Loo et al.: Human metabolic phenotype diversity and its association with diet and blood pressure. Nature 2008:1-6). It was possible to identify urinary metabolites directly linked to animal vs. vegetable protein intake. This is very valuable for future population studies, where diet is an important lifestyle factor but food questionnaires are time-consuming and expensive. Moreover, miss-reporting is a very common problem.

Our hypothesis is to find the same biochemical marker for orange juice as we already found in a preceding nutritional studies where participants recorded orange consumption.

To elucidate the citrus fruit biomarker it needs to be ensured that all volunteers do not consume citrus fruits and foods potentially containing similar ingredients. Therefore it is necessary to ask volunteers to refrain from these foods by giving them dietary restrictions. Extensive literature research showed that some foods (such as grain legumes and brie cheese) may contain the same compound, but in much smaller amounts.

Days 1-3 will be on open diet but with dietary restrictions (no alcohol, cheese, fruits, ethnic foods such as Chinese and Indian food, grain legumes such as beans, lentils, peas and peanuts, and all kinds of sprouts (such as cress or alfalfa)). On day 2 a glass of orange juice (200ml) will be consumed in addition to the open diet. Urine collection will continue and stop on day 4 at 10 am.

During the study to minimise variation in biomarker excretion due to other beverages the participants beverage intake will be restricted to water and coffee.

All urine samples will then be analysed using high resolution NMR spectroscopy and mass spectrometry. Mathematical data analyses as well as the visual examinations of the NMR spectra will also be carried out to validate the presence of citrus fruit biomarkers.

Inclusion Criteria:

• healthy individuals
• male/female
• aged 18-45 years
• non-smoker
• BMI 18-25 kg/m2

Exclusion Criteria:

• regular drug intake
• regular food supplements intake