Ithaca, new York
October 8, 2004
Many onions are chock full of
anti-cancer chemicals. However, certain varieties are
particularly high in these compounds as well as more effective
in inhibiting liver and colon cancer cell growth.
According to a new study by
Cornell University food scientists, led by Rui Hai Liu,
M.D., Ph.D., associate professor of food science, shallots,
Western Yellow, New York Bold and Northern Red onions are higher
in anti-cancer chemicals than other varieties tested.
Furthermore, Liu found that shallots and Western Yellow and New
York Bold onion varieties are particularly effective against
liver cancer cells, while New York Bold and Western Yellow
varieties have the greatest effect on colon cancer cells.
"Our study of 10 onion varieties and shallots clearly shows that
onions and shallots have potent antioxidant and
antiproliferation activities and that the more total phenolic
and flavonoid content an onion has, the stronger its antioxidant
activity and protective effect," says Liu.
Phenolics and flavonoids are types of phytochemicals --
antioxidant chemicals that protect plants against bacteria,
viruses and fungi. Phenolics and flavonoids, like other
antioxidants, help prevent cancer by mopping up cell-damaging
free radicals and inhibiting the production of reactive
substances that could damage normal cells.
The Liu group's study of varietal differences in phenolic and
flavonoid content and antioxidant activities of onions against
cancer cells is online at <http://pubs.acs.org/journals/jafcau/index.html>.
The study also will be published in the October issue of the
Journal of Agricultural and Food Chemistry.
Liu found that shallots had six times the phenolic content of
the onion variety with the lowest content (Vidalia). Western
Yellow onions had 11 times more flavonoids than Western Whites,
the onions with fewest flavonoids.
Using colon cancer cells treated with extracts from the 10 onion
varieties and shallots that were tested, the Liu group found
that New York Bold and Western Yellow onion extracts provided
the strongest anti-proliferation protection against colon cancer
cells. The Western Yellow, shallot
and New York Bold extracts provided the strongest
anti-proliferation protection against liver cancer cells.
"Onions are one of the richest sources of flavonoids in the
human diet," Liu points out. "And flavonoid consumption has been
associated with a reduced risk of cancer, heart disease and
diabetes. Flavonoids are not only anti-cancer but also are known
to be anti-bacterial, anti-viral, anti-allergenic and
anti-inflammatory."
Onions are also the world's second most important horticultural
crop, with an annual retail value in the United States of more
than $3 billion, according to Liu and his co-authors: Jun Yang,
a Cornell graduate student in food science; Katherine J. Meyers,
a Cornell undergraduate student in food science; and Jan Van der
Heide of Cornell Cooperative Extension of Oswego County.
New York state is ranked seventh in total volume of U.S. onion
production, and three of the four of the varieties with the
greatest total phenolic and flavonoid content are grown in the
state (New York Bold, Northern Red and shallots).
"Although milder onions are becoming more popular, the bitter
and more pungent onions seem to have more flavonoid compounds
and appear to be more healthful," says Liu.
Because researchers now believe that about one-third of cancer
cases could be prevented by diet, the National Cancer Institute
and American Cancer Society recommend that Americans consume at
least five servings of fruits and vegetables a day. A number of
other studies have found that phytochemicals and antioxidants
are the chemicals in fruits and vegetables that could be
effective against cardiovascular disease and certain cancers,
such as lung cancer, prostate cancer and melanoma.
The study was funded, in part, by the New York State Department
of Agriculture and Markets.
Related World Wide Web sites: The following sites provide
additional information on this news release. Some might not be
part of the Cornell University community, and Cornell has no
control over their content or availability.
- Rui Hai Liu: <http://www.foodscience.cornell.edu/faculty/liu/liu.htm>
December 16, 2004
ERRATUM
On Oct. 7, Rui Hai Liu, M.D., an
associate professor of food science at Cornell University, and
his colleagues in
Cornell's Department of Food Science published an article in the
Journal of Agricultural and Food Chemistry titled "Varietal
differences in phenolic content and antioxidant and
antiproliferative activities of onions."
The article reported on research indicating that onion types
vary in antioxidant and antiproliferation activity which
inhibits liver and colon cancer cell growth. One of the most
active types was from New York state.
However, when the article was published, an error was made
regarding the designation of the onion type grown in New York
state. The commercial brand name "N.Y. Bold" was used instead of
the more appropriate designations of "pungent yellow onion" or
"yellow cooking onion."
Onions grown and marketed under the N.Y. Bold brand name
represent only one of the onion production areas of the state.
In fact, pungent yellow onions are grown in all onion production
areas of the state. Consequently, the results of Liu's research
apply to all New York-grown pungent yellow onions, the most
commonly grown onion in the state. The research offers all
producers of pungent yellow onions in New York state an
opportunity to market the healthful attributes of this onion
type.
Liu is correcting this error by submitting an erratum to the
Journal of Agricultural and Food Chemistry. This is the standard
procedure used to address errors that appear in the scientific
literature. Likewise, a clarification will appear in the next
issue of CALS Connect. The online Cornell News Service release
about the study also has been corrected.
Related World Wide Web sites: The following website provides
additional information on this news release.
<http://www.news.cornell.edu/releases/Oct04/onions.cancer.ssl.html>
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