What does the “antioxidant capacity” of a product mean?
The answer depends on the environment in which it is tested.
- You can test the product itself. (Is there antioxidant activity in a given chemical reaction?)
- You can test the product in a “cell-based system”. (Do any of the potential antioxidants get into the cells?)
- You can test the product in a human. (Do any of the potential antioxidants find their way into serum?)
Most products that use antioxidants as a marketing claim today base their claims on the first kind of test. This was for a good reason, because until recently it was quite expensive to do batch-to-batch tests in a “cell-based system”.
With the introduction of the CAP-e, “cell-based testing” is now an affordable next step or alternative to the “chemical-based” methods.
Study Design for CAP-e Testing
The CAP-e assay is performed by allowing red blood cells to absorb antioxidants from a physiological liquid containing soluble product. All compounds not absorbed into the cell are then removed. The cell is exposed to oxidative stress. An indicator dye shows the degree of intracellular damage to the cell, in the presence versus absence of serial dilutions of the test product.
Example of Study Design for Bioavailability Testing
Below is a diagram illustrating the involvement of each human subject.
When a cross-over study design is implemented, the relative difference in antioxidant status can be calculated as the difference between “no product” and “product”, i.e. the difference between grey and green data sets for each time point. This value, Delta, is a measure of improved antioxidant status after consumption and is illustrated by the red arrows below.