Two new studies show
that using a lot of water to cook
vegetables can cause them to lose
much of their cancer-fighting antioxidants.
Researchers found blanching, boiling,
or microwaving vegetables in water
caused antioxidants to leak out
of the vegetables and into the cooking
water, but steaming them preserved
most of these valuable nutrients.
Flavonoids, an antioxidant, are
nutrients that are found naturally
in many vegetables. They're thought
to have a variety of healthy effects
in the body by helping to protect
cells from free radicals (unstable
compounds that damage cells).
They found that microwaving the
broccoli in the water for five minutes
at full power produced the greatest
nutrient loss, and the microwaved
broccoli lost 74% to 97% of three
key antioxidants. Boiling also led
to a significant loss of these antioxidants.
In contrast, steaming broccoli over
the water for three and a half minutes
caused only minimal loss of the
three antioxidants (0% to 11%).
Researchers also looked at the effects
of blanching (briefly immersing
in rapidly boiling water) 20 different
types of vegetables before freezing
and storing vegetables.
They found that blanching vegetables
prior to freezing caused a loss
of up to one-third of their antioxidant
content, including vitamin C. Slight
additional losses were detected
during freezer storage. Folic acid
was also very sensitive to the effects
of blanching and more than half
of this vitamin was lost.
Researchers say these effects varied
greatly depending on the vegetable,
but in general vitamins and antioxidants
were much more sensitive to processing
and storage than fiber content,
which was not affected and even
increased slightly after blanching
and freezing in some cases.