No abstract

Peptide bonds of proteins and acetal bonds of carbohydrates are both hydrolyzed enzymatically and non-enzymatically in an acidic environment. A major problem of raising gastric pH permanently is impaired non-enzymatic as well as acid catalyzed cleavage of peptide and glycosidic bonds, i.e. malfunction of proteolysis and hydrolysis of di-, oligo-, and polysaccharides. In the modified gastric environment, drugs and nutritional components may be differently soluble, differently dissociated, and/or differently hydrolyzed, and therefore have modified absorption and bioavailability profiles. The topic is of major public health importance due to high prevalence of gastrointestinal pathologies and number of PPI prescriptions worldwide, estimated to some 120 million annually [3,4]. Multiple factors have an impact on bioavailability of drugs, i.e. [5] • The drug's profile related to solubility and dissolution, i.e. o Dissociation degree o Hydrogen bond building

Nutrients are partially bioaccessible to be extracted from their matrix. They may be partially lost by processing to a meal and by metabolism after absorption from the GI tract. Numerous steps in this cascade have an impact on the nutrient amount which will finally be bioavailable for an effect. Daily allowances are defined and widely recommended to obtain such an effect. However, these needs are derived from observation of healthy populations and are increased to cover needs for special consumer and patient groups or for pregnancy. Daily allowances are subject to frequent changes whenever new scientific evidence arises as is the case for vitamin D. This article describes reasons why generally reasonable recommendations may fail occasionally are found among the variation of genes, age, gender, or race, as well as epigenetics, which all contribute to the individual expression of metabolic capacity and thus to differences in individual bioavailability.