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What Is the Meaning of Bioavailability?

Bioavailability refers to how fast the body absorbs substances like drugs and food. Pharmacy and nutritional sciences use this term. Mathematical formulas determine how fast a drug or food gets absorbed by systematic circulation. When a consumer takes a substance intravenously, bioavailability is 100 percent. In regards to nutritional supplements, bioavailability means the capability of a substance to be absorbed or stored in the body. Four types of bioavailability exist.

  1. Absorption vs. Availability

    • Students, researchers and laymen use these terms inconsistently and clear definitions need to define what each means. The Journal of Pharmakinetics and Pharmadynamis suggests that absorption refers to movement of a drug across the outer mucosal membranes of the GI tract, while bioavailability refers to the availability of a drug to the general circulation or site of pharmacological actions. These two terms vary greatly.

    Bioavailability in Pharmacology

    • In pharmacology, it is relative or absolute bioavailability. Absolute compares intravenous results with non-intravenous results of the same drug. It is a fraction of the absorbed drug. These tests are very expensive. Relative compares one drug with a different formula of the same drug, generics. Generic manufacturers must demonstrate 90 percent effectiveness for the FDA to approve it.

    Bioavailability in Dietary Supplements

    • In dietary supplements, no methods or guidelines exist in measuring and reporting the results. Bioavailability relies on statistics and averages instead of clear fractions that make doctors and consumers aware of the true results.

    Theories/Speculation

    • When people speak of universal and reliable bioavailability, they refer to the results of a specific product. In relative availability that means a trial result with 84 percent positive in those tested. In universal, it means a result of 98 percent positive results. Bioavailability can go back all the way to the soil where growers planted the substance. Affected by chemical properties, soil properties, climate and interaction processes, soil can make substances less bioavailable when consumed.

    Reasons for Variations

    • Variations in nutritional bioavailability can be caused by physical properties; types of drug formation; whether the drug is taken with or without food; health of the stomach; sleep habits of the participant; drug and food interventions; rates of metabolism; and overall health of the participant.

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