Results from observational studies suggest a small beneficial association between protein and blood pressure that may be mainly attributable to the intake of protein from plant sources. In epidemiological studies biomarkers of dietary intake are useful to estimate intake more reliably. Dietary studies using biomarkers of protein intake generally show stronger associations with health outcomes. However, data on biomarkers for specific types of protein (e.g. from dairy, meat, grain and legumes) are scarce. Therefore the purpose of this study is to identify new biomarkers for the intake of protein from meat, dairy and grain. In addition the secondary purpose is to investigate whether intake of protein from these sources influences kidney filtration rate and urinary acid excretion differentially.

Inclusion Criteria:

• Age 18-40 years
• BMI between 18.5 and 30 kg/m2
• Healthy (As judged by the participant)
• Written informed consent obtained

Exclusion Criteria:

• Unable or unwilling to comply with study procedures.
• Unusual dietary patterns, including high alcohol intakes (≥ 2 glasses/day) and a vegetarian diet
• Recent (< 4 weeks) or current participation in a study with any investigational drug or dietary intervention
• Usage of an energy restricted diet during the last two months
• Weight loss or weight gain of 5 kg or more during the last two months
• Smoking
• Stomach or bowel diseases
• Kidney disorders
• Diabetes, thyroid disease, other endocrine disorders
• Prevalent cardiovascular disease
• Extreme sports (>8h/ wk)
• Usage of any prescribed medication except for oral contraceptives
• Use of systemic antibiotics in the period of 3 month prior to the study
• For women: pregnant or lactating
• For women: not using oral contraceptives
• For women: Unwilling to use oral contraceptives for consecutively for at least the total study duration
• Liver function parameters (ALAT, ASAT, and γ-GT) and renal function parameters (Serum creatinin) outside the normal range