Bioavailability factors affecting

FACTORS AFFECTING BIOAVAILABILITY OF TRACE ELEMENTS IN ARID SOILS... 

Factors Affecting Bioavailability of Soil-Sorbed Chemicals.270... 

Nielsen IL, Williamson G. 2007. Review of the factors affecting bioavailability of soy isoflavones in humans. Nutr Cancer 57 1-10. 

Fig. 2 Summary of processes involved following the oral administration of a drug in tablet or capsule form. (From Blanchard, J. Gastrointestinal absorption. II. Formulation factors affecting bioavailability. Am. J. Pharm. 1978, 150, 132-151.)...

If nutrients found in food were digested, absorbed, and made available to the human or animal body at the 100% level, the science and practice of nutrition would be indeed simplified. That nutrients vary in their bioavailability has been well established. The chemical nature of the specific form of the nutrient involved, the chemical and physical characteristics of the foods in which nutrients are contained, other constituents of the diet, the nature of the digestive and absorptive processes for the specific nutrients, and the physiological condition of the person consuming the food all may affect bioavailability. However, knowledge of specific individual and interacting factors affecting bioavailability and utilization of nutrients has not yet been fully elucidated and constitutes one of the most active areas of current nutrition research. 

The beginning chapters of this volume are devoted to aspects of phytochemical research that are fundamental to this new era of activity. Chapter 1 introduces the fundamentals of nutritional genomics (nutrigenomics), notably DNA arrays, proteomics, and metabolomics, while Chapter 2 indicates the manifold factors affecting bioavailability, critically compares various methods for its measurement, and highlights crucial differences between studies on new drug formulations and dietary phytochemicals. The fundamental importance of considering metabolic processes is addressed in Chapter 3, with particular attention to those associated with the ubiquitous polyphenols. 

Iron deficiency was not a major factor affecting bioavailable Cu and Zn (Table 6, Fig. 5). Copper and Zn uptake by Fe-deficient plants was reduced because of the 25-50% decrease in biomass that occurred relative to Fe-sufficient plants (Table 3). Despite substantial decreases in biomass, Fe deficiency resulted in similar or greater amounts of Cu and Zn being absorbed by plants, relative to Fe-sufficient plants. This may be a consequence of enhanced exudation of phy-tosiderophores as a response to Fe deficiency (Fig. 2), as shown for wheat grown in a Cu-contaminated, calcareous soil (Chaignon et al., 2002b). 

Factors affecting bioavailability may be classified into two general categories ... 

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