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Growers can boost broccoli and tomato benefits

May 26, 2010 – A
University of Illinois study has demonstrated that agronomic practices can
greatly increase the cancer-preventive phytochemicals in broccoli and tomatoes.

May 26, 2010 – A
University of Illinois study has demonstrated that agronomic practices can
greatly increase the cancer-preventive phytochemicals in broccoli and tomatoes.

“We enriched preharvest
broccoli with different bioactive components, then assessed the levels of
cancer-fighting enzymes in rats that ate powders made from these crops,” said
Elizabeth Jeffery, a University of Illinois professor of food science and human
nutrition.

The highest levels of detoxifying
enzymes were found in rats that ate selenium-treated broccoli. The amount of
one of the cancer-fighting compounds in broccoli was six times higher in
selenium-enriched broccoli than in standard broccoli powder, she said.

Selenium-treated broccoli
was also most active in the liver, reaching a level of bioactivity that
exceeded the other foods used in the experiment.

“We were intrigued to find
that selenium initiated this amount of bioactivity,” she said.

Along with garlic and
other plants of the allium family, broccoli and other plants of the brassica
family are unique in having a methylating enzyme that enables plants to store
high concentrations of selenium, she said.

“Our bodies need a certain
amount of selenium, but many areas of the world, including parts of the United
States and vast areas of China, have very little selenium in the soil,” she
said.

“Not only could selenium
in broccoli deliver this necessary mineral, it also appears to rev up the
vegetable's cancer-fighting power,” she added.

Jeffery is now working to
determine whether selenium compounds are directly responsible for the increase
in bioactivity or if selenium acts indirectly by directing new synthesis of the
broccoli bioactives called glucosinolates.

In a previous study, Jeffery
and University of Illinois colleague John W. Erdman Jr. showed that tomato and
broccoli powders eaten together are more effective in slowing prostate cancer
in laboratory rats than either tomato or broccoli alone.

In their current research,
they are experimenting with ways to increase the bioactive components in these
foods in order to test the efficacy of enriched broccoli and tomatoes in a new
prostate cancer study.

Rats were fed diets with
food powders containing 10 per cent of either standard broccoli; standard
tomato; lycopene-enriched tomato; tomato enriched with lycopene and other
carotenoids; broccoli sprouts, which contain very high levels of
cancer-fighting compounds; or broccoli grown on soil treated with selenium.

The scientists found that
greater amounts of bioactive components in the food powders translated into
increased levels of the compounds in body tissue and increased bioactivity in
the animals.

Carotenoid-enriched
tomatoes produced more bioactivity in the liver than lycopene-enriched or
standard tomatoes, yielding the most cancer-preventive benefits.

“Carotenoids, which are
phytochemical pigments found in fruits and vegetables, are thought to be
excellent antioxidants and effective in cancer prevention,” said Ann G. Liu, a
University of Illinois graduate student who worked on the study.

“A good rule is: the
brighter the colour, the higher the carotenoid content. If you’re growing or
buying tomatoes, select plants or produce that are a very bright red.
High-lycopene tomatoes are now available through garden catalogs,” she added.

“This research shows that
you can greatly increase a food’s bioactive benefits through normal farming
practices, without resorting to genetic engineering. Farmers have traditionally
been more concerned about yield than nutritional composition. Now we’re asking,
can we grow more nutritional broccoli and tomatoes? And the answer is a
definite yes,” said Jeffery.

The study was published in
the Journal of Agricultural and Food Chemistry. Liu and Sonja E. Volker
co-authored the paper with Jeffery and Erdman.