Health & Cell Biology
Bioavailability: what it means really absorb
Ingesting is not the same as absorbing. And absorbing is not the same as utilising. What science says about the fraction of a substance that actually reaches the cells.
Conceptual introduction
When it comes to supplements, the attention usually goes straight to the dose: how many milligrams, how many capsules to take, what concentration. But there's a more important question, one that's often overlooked:
how much of this substance is actually absorbed by the body?
Because ingesting is not the same as absorbing. And absorbing is not the same as utilising. This is where the concept of bioavailability comes in.
What is bioavailability
Bioavailability refers to fraction of a substance that enters the systemic circulation and becomes available to exert a biological effect.
Simply put:
- Part of what we eat is not absorbed
- Another part is absorbed, but doesn't reach the cells
- Only a fraction is effectively utilised by the body
This process depends on several factors:
- chemical form of the substance
- matrix in which it is inserted
- digestion and intestinal absorption
- hepatic metabolism
- transport in the blood
Two supplements with the same dose on the label can have completely different impacts.
The specific case of astaxanthin
Astaxanthin is a molecule lipophilic (fat-soluble). In its most common form (fat-soluble):
- needs fat in the meal to be absorbed
- depends on the formation of micelles in the intestine
- follows absorption pathways similar to those of lipids
In practice, this means
- absorption varies from person to person
- depends on what you ate at the meal
- can be inconsistent over time
Under certain conditions, absorption can be significantly reduced.
Delivery method and impact on absorption
To understand bioavailability, it is essential to look at how the substance is presented to the body. Astaxanthin is by nature a lipophilic molecule. In its traditional form (fat-soluble), absorption takes place mainly in the small intestine and depends on a specific process:
- presence of fat in the meal
- emulsification by bile salts
- micelle formation
- subsequent intestinal absorption
This process is efficient, but is not constant. It depends on factors such as the composition of the meal, individual digestion and the functioning of the biliary system.
In formulations that allow dispersion in aqueous media (often referred to as water-soluble or dispersible), astaxanthin is presented differently to the body.
Under these conditions:
- dispersion in the intestinal contents is more homogeneous
- dependence on dietary fat is reduced
- contact with the intestinal absorption surface tends to be more efficient
The result is not a change in the site of absorption, which remains predominantly intestinal, but rather a change in the how the molecule arrives at this process. This can translate into more consistent absorption over time.
Variability vs consistency
An important point, often overlooked, is this:
it's not just the amount absorbed that matters, but the consistency of this absorption over time.
- one day there may be good absorption
- another day, with a different meal, there may be less
- creates variability
- absorption tends to be more predictable
- the process becomes more stable
- less dependence on meals
Practical relevance
What does this mean in practice?
This means that comparing supplements by milligrams alone can be misleading. Two products with the same dose:
- may not deliver the same amount to the body
- may not have the same consistency over time
In the context of cell protection, which is a continuous process, consistency tends to be more relevant than occasional peaks in absorption.
Clear overview
- Bioavailability is not what you ingest, it's what the body uses
- Astaxanthin, in its traditional form, depends on fat to be absorbed
- This introduces variability
- Formulations that reduce this dependence tend to offer greater consistency
- Comparison by milligrams alone is insufficient
If you want to delve deeper into this topic and understand how to assess the quality and absorption of a supplement in a practical way, you can consult the guide:
“How to choose astaxanthin wisely”- Østerlie, M., Bjerkeng, B., & Liaaen-Jensen, S. (2000). Plasma appearance and distribution of astaxanthin E/Z and R/S isomers in plasma lipoproteins of men after single dose administration. Biochemical and Biophysical Research Communications.
- Hussein, G., et al. (2006). Antihypertensive and neuroprotective effects of astaxanthin in experimental animals. Biological & Pharmaceutical Bulletin.
- Fassett, R. G., & Coombes, J. S. (2011). Astaxanthin: a potential therapeutic agent in cardiovascular disease. Marine Drugs.
- Choi, H. D., et al. (2011). Bioavailability of astaxanthin in humans. British Journal of Nutrition.
- Kidd, P. (2011). Astaxanthin, cell membrane nutrient with diverse clinical benefits. Alternative Medicine Review.