Black chokeberries or "aronia" (Aronia melanocarpa),
one of Nature's richest sources of antioxidant phenolics
[follow the Wikipedia links]
We have been interested in berry phytochemicals because they represent dietary options for obtaining antioxidant value from our food choices.
For background from the Berry Doctor's Journal, see this 8-part series on berry anthocyanins and their potential for antioxidant and anti-disease effects, click!
But in science, we want to hear all points of view, especially those that challenge a doctrine -- even the theory that health benefits can be provided by berry antioxidants.
This is the objective of this essay and the next two -- present counterpoints to what we believe -- let's call them anti-theories.
Here's the first surprising
antioxidant anti-theory:
our bodies see berry anthocyanins and other flavonoids as
unwanted chemicals, so actively get rid of them
Introduction
To make two points with this essay, some scientific jargon needs to be explained first. Have patience -- this gets easier below!
Definitions
Anthocyanins: a group of about 600 chemicals making up colorful pigments in the plant kingdom
Flavonoids: the general parent class of anthocyanins and other secondary phenolics, about 6000 in number
Point #1
[Anthocyanins and flavonoids are pigments with significant potential for contributing
to human health by reducing disease risk -- click for a review!]
Following a meal rich in anthocyanins (the phytochemicals responsible for berry skin colors), blood levels peak about 2 hours after eating.
By monitoring urine excretion of anthocyanins, only 3% of the amount ingested can be detected 24 hours later. This fraction would be called "bioavailable", meaning they remained intact in the body, ready to be used as required.
But only 3%!
Example publication, click!
Anthocyanin-rich elderberries (Sambucus nigra L.)
In other words, some 97% of anthocyanins eaten are either metabolized or excreted within 24 hours. This means that most consumed anthocyanins are changed in the body or eliminated.
Why would something valuable to the body
be excreted so readily?
Point #2
There are thought to be around 600 distinct anthocyanins, so there are many chemical variations, indicating some may be absorbed more quickly and easily for use in our cells.
Many anthocyanins are "acylated" ("eh-sill-ated"), a chemical term meaning constructed of chemical groups called acyls which make them much less absorbable. That is, they would be easily excreted.
Non-acylated flavonoids are at least four times more bioavailable, or absorbed, than acylated ones.
Example of a non-acylated flavonoid: resveratrol
Examples of an acylated flavonoid: ellagic acid or an anthocyanin like cyanidin
Berry and cherry colors indicate presence of anthocyanins
Three Surprising Conclusions
1. some anthocyanins -- the non-acylated ones -- are preferred for use in the body; most, however, are rapidly eliminated. Apparently, our bodies want to get rid of unnecessary anthocyanins making up some 97% of the amount we eat in colorful foods
Example publication, click!
2. not all anthocyanins or flavonoids have the same chemical structure; those without the preferred structure are excreted
3. so what are the retained anthocyanins and flavonoids doing for our health? Only speculation exists* and not all roles are related to antioxidant protection -- some of these mechanisms may be at work -- click!
* one of the most interesting theories is that small quantities of flavonoids and anthocyanins
act to immunize, sensitize and stimulate the body's defenses against disease mechanisms,
i.e. not strictly an antioxidant role.
This is similar to getting a flu shot -- a small amount of flu virus injected
into our system actually sensitizes body defenses against other viruses.
