Many of our vegetable sources of nutrition are
rich in pigments called flavonoids, or bioflavonoids, that
are not only colorful and attractive but are also important
sources of health benefits. They help to prevent serious diseases
and the degenerative problems associated with oxidative free-radical
damage. Hundreds, if not thousands, of these flavonoids occur
in plants that are common in ethnic diets around the world.
Unfortunately, Americans eat very few fruits and vegetables,
so they miss the many benefits of these substances. (The most
common "vegetable" that kids eat today isyou
guessed it, french fries! which is not really a vegetable
at all, but a carrier for highly processed and overcooked
hydrogenated fats, while potatoes themselves have virtually
no fat.) Even more exciting, the medical literature now supports
the view that supplements of flavonoids can be healing substances
that can substitute for drugs for many patients or reduce
the doses of medication that they need. Many of the flavonoids
have recently been included in the term "phytochemicals,"
which just means "plant chemicals." Flavonoids protect
against cancer and heart disease and they enhance the activity
of vitamin C.
One good example is quercetin. It is a yellow-green
flavonoid found in red and yellow onions (but not in white
onions), although the amounts found in foods are relatively
small compared to therapeutic doses. In allergic reactions,
histamine is released from mast cells in the tissues. The
membranes of these cells are stabilized by quercetin, so their
histamine is not released as readily, thus reducing the allergic
response. (Interestingly, a synthetic flavonoid called "cromolyn
sodium" is used for allergies under the brand name Intal®).
Effective doses of quercetin range from 800-1200 mg daily,
far higher than the amount found in foods. This is important
because sometimes people may try supplements in too low a
dose, and then give up without getting results.
Return to Ask Dr. J. index