Bioavailability
In plain language
A label tells you hów much of a substance is in the product — but that says nothing about how much your body actually uses. Bioavailability is precisely that difference: the portion of an ingested substance that genuinely becomes available to do something.
Many substances are broken down along the way, poorly absorbed, or only become active after your microbiome converts them. A polyphenol from a plant, for example, often only becomes useful after gut bacteria have converted it into smaller, absorbable metabolites. That is why a product with a high dose can, in practice, deliver less than a lower dose that is cleverly formulated to be released in the right place. The key message: it is not the amount in the jar that counts, but how much áctually reaches the host or the micro-organisms.
The science behind
Bioavailability describes what proportion of an ingested substance reaches the systemic circulation — or the site of action — and how quickly. It is determined by a chain of steps: solubility, stability against stomach acid and enzymes, absorption through the gut wall, and first-pass metabolism in the liver. For many bioactives, and certainly for plant compounds such as polyphenols, absorption in unchanged form is low; their effect depends heavily on what happens to them along the way.
This is exactly where the distinction between bioaccessibility (being released from the matrix and becoming available in the gut) and bioavailability (being effectively absorbed or converted) matters. For numerous plant compounds the active route runs via the microbiome: gut bacteria convert parent compounds into smaller, more readily absorbable or biologically more active metabolites. As a result, not only your intake but also the composition of your microbiome helps determine how much effect you get from the same substance.
Viewed through co-metabolism, then, bioavailability is not a property of the substance alone, but of the interaction between substance, formulation, host and microbiome together. That explains why formulation techniques — clever combining, protecting and targeted release — can make the difference: they steer the substance to the place where absorption or microbial conversion works best. The practical lesson is consistent: release, timing and interaction often weigh more heavily than the gross dose. This reading is supportive and observational — not a medical diagnosis.
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See the books →Scientific references
• Manach C., et al. (2004) — Polyphenols: food sources and bioavailability. Am J Clin Nutr.
• Koppel N., et al. (2017) — Chemical transformation of xenobiotics by the human gut microbiota. Science.
• Van Gucht P. — FORMULA (COSMO trilogy): release, timing and interaction.
Frequently asked questions
- What is bioavailability?
- The extent ánd speed with which an ingested substance actually becomes available to the body or the microbiome.
- Why doesn't the dose tell the whole story?
- Because part of a substance is lost along the way or only becomes active after absorption or microbial conversion.
- What is the difference from bioaccessibility?
- Bioaccessibility is being released and becoming available in the gut; bioavailability is being effectively absorbed or converted.
- Does my microbiome play a role?
- Yes — for many plant compounds, microbial conversion helps determine how much effect you get from the same substance.
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