Bioavailability: Why the Dose on the Label Is Not the Dose You Get

The amount printed on a supplement label is the amount in the capsule, not the amount that reaches your bloodstream, and the gap can be enormous.

What determines it

Bioavailability is the proportion of an ingested dose that reaches systemic circulation in active form. It is affected by solubility, stability in stomach acid, intestinal permeability, efflux transporters that pump compounds back into the gut lumen, and first-pass metabolism in the gut wall and liver. Curcumin is the standard example: notoriously poorly absorbed, rapidly metabolised, and the subject of an entire formulation industry addressing that.

What changes it

Food is a major variable. Fat-soluble compounds absorb substantially better with a fat-containing meal. Some compounds compete with dietary components for transport. Stomach acid matters, so acid-reducing medication can alter absorption of some nutrients including B12 and certain minerals. Particle size and formulation affect dissolution. And individual variation is substantial, driven by gut microbiome composition, transit time and genetic differences in metabolising enzymes.

Formulation approaches and their claims

Liposomal delivery encapsulates the compound in phospholipid vesicles. Piperine from black pepper inhibits certain metabolising enzymes and is added to curcumin products for that reason. Phytosome complexes bind botanical extracts to phospholipids. Nanoemulsions reduce particle size. Some of these have real supporting data; others are marketing applied to a formulation with no comparative testing. The question to ask is whether a head-to-head absorption study exists for that specific product.

If you are considering Cognizil

Read the Cognizil ingredients page before ordering and check the guarantee terms. If you take any prescription medicine — including hormonal contraception — show the label to a pharmacist first, because the St. John’s Wort content genuinely matters. Our buyer’s checklist sets out twelve checks worth running.