Non-bioavailability

Non-bioavailability refers to the extent and rate at which a substance, such as a drug, nutrient, or environmental contaminant, is *not* absorbed into the bloodstream or transported to its intended site of action within the body. It encompasses various factors hindering absorption, including poor solubility, insufficient intestinal permeability, metabolic degradation before reaching the systemic circulation (first-pass metabolism), binding to food components, or active efflux from cells. Consequently, non-bioavailability reduces the therapeutic effect of a drug or the nutritional benefit of a nutrient and can exacerbate the harmful effects of a toxin. It is a critical consideration in drug development, nutritional science, and environmental health risk assessment.

Non-bioavailability meaning with examples

• The pharmaceutical company was concerned about the non-bioavailability of their new oral antibiotic. Despite promising in vitro results, animal studies showed poor absorption due to the drug's rapid degradation in the gut. This issue necessitated a reformulation to improve its stability and transport across the intestinal barrier, ensuring effective treatment of bacterial infections, and increasing its efficacy in patients. This highlights how important it is to take non-bioavailability into consideration.
• Researchers investigating a specific soil contaminant found significant non-bioavailability in plants. Although the toxin was present in the soil, its chemical form made it difficult for plant roots to absorb it and translocate it to the plant's edible parts. This discovery mitigated concerns about the extent of contamination in the food chain, since the toxins were not available to the plant. This situation exemplified that all contaminants do not have bioavailable consequences.
• Patients with cystic fibrosis often experience impaired fat absorption and hence, non-bioavailability of fat-soluble vitamins (A, D, E, and K). This malabsorption leads to deficiencies that can cause serious health complications. Doctors typically prescribe supplemental vitamins in an effort to overcome the patients' challenges in their nutritional needs. Furthermore, they help make changes to a patient's diet by recommending nutrient-dense foods.
• In an attempt to improve the nutritional value of a fortified food product, scientists tested the iron's bioavailability. They discovered that adding calcium to the product caused a substantial reduction in iron bioavailability due to competition for absorption in the gut, resulting in a decreased absorption of iron. This research demonstrates the complex interactions of various food components that contribute to a final assessment of non-bioavailability of a key nutrient.