BBC SCIENCE FOCUS MAGAZINE COLLECTION 23DIETcancer. The science is not so straightforward.
“Many free radicals play important, positive
roles in cell biology and human physiology,”
says Dr Blumberg. “But in excessive amounts
( genera l ly refer red to a s ‘ox idat ive st ress’) t hey
can damage cell constituents, such as lipids,
proteins and DNA, and contribute both to the
aging process and the development of many
chronic diseases, including cancer. But, this
simple concept is actually extraordinarily
complex and incompletely understood.”
For one thing, more is not always better.
“While consuming more antioxidant-rich fruits,
vegetables, whole grains, nuts and seeds can
certainly be good, everything can be harmful
at a high enough intake,” says Dr Blumberg.
One study on people at risk of developing lu ng
cancer had to be stopped because those given
antioxidants were dying more quickly. But
while a diet that is high in antioxidant-rich
produce probably won’t do you much harm –
unless you consume them in wine form – it
won’t necessarily do you that much good either.
“While antioxidants are what marketers focus
on, the science does not indicate that they’re
the most important part of a food’s nutritional
repertoire,” says Kamal Patel, a nutrition
researcher and director of Examine.com, an
independent study analysis website. “The US
federal government used to use the oxygen
radical absorbance capacity antioxidant scale,
but no longer does due to lack of support for
its impact on health.”
Nor will the presence of high levels of
antioxidants in a food, super or otherwise,
necessarily result in a proportional antioxidant
effect. For example, anthocyanins, found in
blueberries – often referred to as the grandaddy
of the superfood movement, have been shown
to inhibit growth of cancerous human colon
cells in vitro. But there’s no evidence that
the flavonoids, the class of antioxidants that
anthocyanins belong to, are even absorbed in
the human body – indeed, studies show that
less than five per cent survives consumption
and is promptly excreted.
“When you consume an antioxidant, the main
antioxidant effect often comes from your body’s
reaction to eating a foreign substance, rather
than from the substance itself,” says Patel. 5