Metabolism is controlled by macro- and micronutrients. Protein-rich diets should lead to latent acidosis at tissue level with further negative implications. Food supplements with alkaline salts are available and popular pretending to prevent these changes.

Within a randomized double-blind placebo-controlled trial, the investigators tested the hypotheses 1) that a 4-week protein-rich diet induces a latent tissue acidosis and 2) an alkaline supplement can compensate this. Acid-base balance and important metabolic parameters were determined before and after 4 weeks of supplementation by peripheral blood samples, indirect calorimetry and muscle microdialysis before and after a protein-rich test meal.

Inclusion Criteria:

• slightly reduced kidney function (GFR 60-89 ml/min)
• Body mass index 20.0 - 29.9 kg/m2
• normal daily diet composition: 45-50, 35-40, and 15 E% from carbs, fats and proteins, respectively

Exclusion Criteria:

• sorbitol-/fructose-intolerance
• intake of antacidic drugs
• vegetarians, vegans
• intake of any nutritional supplements
• any cardiovascular, pulmonary, endocrine or metabolic diseases
• any drug abuse
• intake of any anticoagulant drugs