Bioavailability: Unlocking the Full Potential of Drugs and Supplements
May 05, 2023
Introduction
Bioavailability is a critical concept to understand for anyone interested in the fields of medicine, nutrition, and overall health. It refers to the degree and rate at which a substance, such as a drug, herbal supplement, or mineral, is absorbed into the bloodstream and becomes available at the site of action. Understanding bioavailability is essential because it influences the effectiveness of medications and supplements, ensuring you get the most out of these products. In this blog, we will delve into the concept of bioavailability, the factors that determine it, and examples related to drug or supplement absorption in the gastrointestinal (GI) tract. By the end, you'll be well-equipped to make more informed decisions about your health and wellness.
What is Bioavailability?
Bioavailability is a term used to describe the extent to which a substance, such as a drug, mineral, or herbal supplement, is absorbed by the body and becomes available to produce its intended effect (1). It is typically expressed as a percentage, with higher percentages indicating that more of the substance is available for use by the body. Bioavailability gives you information on the degree to which a given nutrient, drug, or supplement is absorbed into your body's system where it can be used in biochemical or physiologic reactions that help your body function.
In the context of drugs, bioavailability is a critical factor in determining dosage and efficacy. When a drug has low bioavailability, it may require higher doses to produce the desired effect, which can increase the risk of side effects (2). On the other hand, high bioavailability means the drug can be used effectively at lower doses, potentially reducing the risk of adverse reactions.
For minerals and herbal supplements, bioavailability is crucial in determining the nutritional benefits of these products. Some minerals and herbal constituents may have low bioavailability due to factors such as poor absorption, rapid excretion, or interactions with other substances (3). Understanding the bioavailability of these products can help you make more informed decisions about your health and wellness.
Factors that Determine Bioavailability
Several factors influence the bioavailability of drugs, minerals, and herbal supplements. Some of the key factors include:
- Absorption: The process by which a substance moves from the site of administration (e.g., the GI tract) into the bloodstream (4). Factors such as the chemical properties of the substance, the presence of food or other substances in the GI tract, and individual variations in GI function can affect absorption. For example, the solubility and permeability of a drug can influence its absorption rate, with highly soluble and permeable drugs typically having better absorption (5).
- Distribution: The process by which a substance is transported throughout the body via the bloodstream (6). Factors such as blood flow, tissue permeability, and the affinity of a substance for specific tissues can influence distribution. For example, drugs that are highly bound to plasma proteins may have limited distribution to tissues, potentially reducing their overall bioavailability (7).
- Metabolism: The process by which a substance is broken down and converted into other compounds, often in the liver (8). Metabolic processes can inactivate a substance or convert it into a more or less active form, affecting its overall bioavailability. Factors such as genetic variations in metabolic enzymes and the presence of other drugs or substances that can inhibit or induce these enzymes can impact metabolism and, subsequently, bioavailability (9).
- Excretion: The process by which a substance is eliminated from the body, primarily through the kidneys and GI tract (10). Excretion rates can influence how long a substance remains in the body and its bioavailability. Factors such as kidney function and the presence of other substances that can compete for elimination pathways can impact excretion (11).
Examples of Bioavailability and Drug or Supplement Absorption in the GI Tract
- Oral medications: When a drug is taken orally, it must first pass through the GI tract and be absorbed into the bloodstream before it can reach its intended target (12). Factors such as stomach acid, bile salts, and intestinal bacteria can affect the bioavailability of oral medications. For example, some drugs are poorly absorbed in the presence of food, while others may require food to enhance absorption (13). Additionally, people with kidney disease need to be cautious when taking medications or supplements, as impaired kidney function can impact the excretion of these substances, potentially leading to toxic levels in the body (14).
- Minerals: The bioavailability of minerals can be influenced by factors such as the form in which they are consumed (e.g., inorganic vs. organic), the presence of other minerals or substances that can interfere with absorption, and individual differences in mineral metabolism (15). For example, iron absorption can be enhanced by the presence of vitamin C, while phytates found in certain plant-based foods (e.g., beans, seeds, nuts, and grains) can inhibit the absorption of minerals like zinc and calcium (16). It is important to be aware that individuals with kidney disease should be particularly careful when taking mineral supplements, as their bodies may have difficulty eliminating excess minerals, potentially leading to toxic levels (17).
- Herbal supplements: The bioavailability of herbal supplements can be affected by factors such as the extraction method used to obtain the active constituents, the presence of other compounds in the supplement that may interfere with absorption, and individual differences in metabolism (18). For instance, the bioavailability of curcumin, an active compound found in turmeric, can be significantly enhanced by the addition of piperine, a compound found in black pepper (19). As with all foods, supplements, vitamins, and drugs, I recommend that people with kidney disease should consult their healthcare providers before taking herbal supplements, as some herbs may harm kidney function or interact with medications prescribed for kidney disease (20).
Future Areas of Research in Supplement Research and Bioavailability
As our understanding of bioavailability continues to evolve, researchers are exploring new ways to improve the absorption and effectiveness of drugs, minerals, and herbal supplements. Some promising areas of future research include:
- Nanotechnology: The use of nanoparticles to improve the delivery and absorption of drugs and supplements, potentially increasing their bioavailability and reducing the need for higher doses (21).
- Probiotics and prebiotics: The study of how beneficial bacteria and their preferred food sources in the GI tract can influence the absorption and metabolism of drugs, minerals, and herbal supplements (22).
- Drug and supplement interactions: Further research into how various substances interact with one another in the body, leads to a better understanding of factors that can enhance or inhibit bioavailability (23).
- Personalized medicine and nutrition: The development of individualized drug and supplement regimens based on factors such as genetics, lifestyle, and health status, leading to more effective and targeted therapies (24). This approach could be particularly useful for individuals with kidney disease, allowing for tailored treatment plans that minimize the risk of adverse effects related to impaired kidney function.
Conclusion
Understanding the concept of bioavailability is essential for anyone interested in making informed decisions about their health and wellness. It allows us to maximize the benefits of drugs, minerals, and herbal supplements by ensuring that these substances are effectively absorbed and utilized by our bodies. By staying up-to-date on the latest research and innovations in the field, we can continue to improve our knowledge of bioavailability and make better choices for our overall health. Individuals with kidney disease should be particularly cautious when taking medications or supplements, as their impaired kidney function may impact the excretion and overall bioavailability of these substances.
References
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- Lennernäs, H. (2003). Clinical pharmacokinetics of atorvastatin. Clinical Pharmacokinetics, 42(13), 1141-1160.
- Gibson, R. S. (2003). The role of diet- and host-related factors in nutrient bioavailability and thus in nutrient-based dietary requirement estimates. Food and Nutrition Bulletin, 24(1), 77-100.
- Lentner, C. (Ed.). (1984). Geigy Scientific Tables, Physical Chemistry. Composition of the Blood. Haematology. Human Somatometric Data. 1984, 359 pp. (Vol. 3). Ciba-Geigy.
- Yu, L. X., & Amidon, G. L. (1999). A compartmental absorption and transit model for estimating oral drug absorption. International Journal of Pharmaceutics, 186(2), 119-125.
- Levitt, D. G., & Levitt, M. D. (2016). Human serum albumin homeostasis: a new look at the roles of synthesis, catabolism, renal and gastrointestinal excretion, and the clinical value of serum albumin measurements. International Journal of General Medicine, 9, 229-255.
- Davies, B., & Morris, T. (1993). Physiological parameters in laboratory animals and humans. Pharmaceutical Research, 10(7), 1093-1095.
- Dressman, J. B., & Reppas, C. (2000). In vitro-in vivo correlations for lipophilic, poorly water-soluble drugs. European Journal of Pharmaceutical Sciences, 11, S73-S80.
- Charman, W. N., & Stella, V. J. (1986). Estimating the maximal potential for intestinal lymphatic transport of lipophilic drug molecules. International Journal of Pharmaceutics, 34(1-2), 175-178.
- Hambidge, M. (2003). Biomarkers of trace mineral intake and status. The Journal of Nutrition, 133(3), 948S-955S.
- Hallberg, L., Brune, M., & Rossander, L. (1989). Iron absorption in man: ascorbic acid and dose-dependent inhibition by phytate. The American Journal of Clinical Nutrition, 49(1), 140-144.
- Williamson, E. M. (2001). Synergy and other interactions in phytomedicines. Phytomedicine, 8(5), 401-409.
- Shoba, G., Joy, D., Joseph, T., Majeed, M., Rajendran, R., & Srinivas, P. S. (1998). Influence of piperine on the pharmacokinetics of curcumin in animals and human volunteers. Planta Medica, 64(04), 353-356.
- Stevens, P.E., & Levin, A. (2013). Evaluation and management of chronic kidney disease: Synopsis of the kidney disease: improving global outcomes 2012 clinical practice guideline. Annals of Internal Medicine, 158(11), 825-830.
- Rhee, E. P., & Thadhani, R. (2011). New insights into uremia-induced alterations in metabolic pathways. Current Opinion in Nephrology and Hypertension, 20(6), 593-598.
- St-Jules, D. E., Goldfarb, D. S., & Sevick, M. A. (2016). Nutrient non-equivalence: Does restricting high-potassium plant foods help to prevent hyperkalemia in hemodialysis patients? Journal of Renal Nutrition, 26(5), 282-7.
- Brown AC. Kidney toxicity related to herbs and dietary supplements: Online table of case reports. Part 3 of 5 series. Food Chem Toxicol. 2017;107(Pt A):502-519.
- Dangi P, Chaudhary N, Chaudhary V, et al. Nanotechnology impacting probiotics and prebiotics: a paradigm shift in nutraceuticals technology. Int J Food Microbiol. 2023;388:110083.
- Balakumar P, Alqahtani T, Alqahtani A, et al. A Unifying Perspective in Blunting the Limited Oral Bioavailability of Curcumin: A Succinct Look. Curr Drug Metab. 2022;23(11):897-904
- Nowack R. Herb-drug interactions in nephrology: documented and theoretical. Clin Nephrol. 2008;69(5):319-325.
- Yu, L. X., & Amidon, G. L. (1999). A compartmental absorption and transit model for estimating oral drug absorption. International Journal of Pharmaceutics, 186(2), 119-125.
- Levitt, D. G., & Levitt, M. D. (2016). Human serum albumin homeostasis: a new look at the roles of synthesis, catabolism, renal and gastrointestinal excretion, and the clinical value of serum albumin measurements. International Journal of General Medicine, 9, 229-255.
- Davies, B., & Morris, T. (1993). Physiological parameters in laboratory animals and humans. Pharmaceutical Research, 10(7), 1093-1095.
- Ginsburg, G. S., & Phillips, K. A. (2018). Precision medicine: from science to value. Health Affairs, 37(5), 694-701.
