Columbus, Ohio
February 27, 2007
Deep red tomatoes get their rich
color from lycopene, a disease-fighting antioxidant. A new
study, however, suggests that a special variety of
orange-colored tomatoes provide a different form of lycopene,
one that our bodies may more readily use.
Researchers found that eating spaghetti covered in sauce made
from these orange tomatoes, called Tangerine tomatoes, caused a
noticeable boost in this form of lycopene in participants'
blood.
“While red tomatoes contain far more lycopene than orange
tomatoes, most of it is in a form that the body doesn't absorb
well,” said Steven Schwartz, the study's lead author and a
professor of food
science and technology at Ohio State University.
“The people in the study actually consumed less lycopene when
they ate sauce made from the orange tomatoes, but they absorbed
far more lycopene than they would have if it had come from red
tomatoes,” he said. “That's what is so dramatic about it.”
The tomatoes used for this work were developed specifically for
the study – these particular varieties aren't readily available
in grocery stores. The researchers suggest that interested
consumers seek out orange- and gold-colored heirloom tomatoes as
an alternative to Tangerine tomatoes, but caution that they
haven't tested how much or what kind of lycopene these varieties
contain.
Lycopene belongs to a family of antioxidants called the
carotenoids, which give certain fruits and vegetables their
distinctive colors. Carotenoids are thought to have a number of
health benefits, such as reducing the risk of developing cancer,
cardiovascular disease and macular degeneration.
“The tomato is a wonderful biosynthetic factory for carotenoids,
and scientists are working on ways to enhance the fruit's
antioxidant content and composition,” Schwartz continued.
The findings appear in a recent issue of the
Journal
of Agricultural and Food Chemistry.
Lycopene is a carotenoid that contains a variety of related
compounds called isomers. Isomers share the same chemical
formula, yet differ in chemical structure. In the case of
tomatoes, the different lycopene isomers play a part in
determining the color of the fruit.
Several years ago, Schwartz and his colleagues discovered the
abundance of several of these isomers, called cis- lycopenes, in
human blood. But most of the tomatoes and tomato-based products
we currently consume are rich in all-trans-lycopene.
“We don't know why our bodies seem to transform lycopene into
cis-isomers, or if some isomers are more beneficial than
others,” Schwartz said.
The researchers don't know if tomatoes rich in cis-lycopene
would provide greater health benefits to humans, but the study's
results suggest that tomatoes can be used to increase both the
intake and absorption of the health-beneficial compounds.
The researchers made spaghetti sauce from two tomato varieties –
tangerine tomatoes, which get their name from their orange skin
and are high in cis-lycopene, and a tomato variety chosen for
its rich beta carotene content.
The tomatoes were grown at an Ohio State-affiliated agricultural
research station in northwestern Ohio. Following harvest, both
tomato varieties were immediately processed into canned tomato
juice and concentrated. Italian seasoning was added for taste.
The 12 adults participating in the study ate two spaghetti test
meals – one included sauce made from tangerine tomatoes, while
the other featured sauce made from the tomatoes high in beta
carotene. The participants were asked to avoid tomato and beta
carotene-rich foods for 13 days before eating each test meal.
Researchers drew blood right before each participant ate and
again every hour or two up to 10 hours after the meal. They
analyzed the blood samples for lycopene and beta carotene
content.
Lycopene absorption from the tangerine tomatoes was 2.5 times
higher than that absorbed from the beta carotene-rich tomatoes
and, Schwartz said, from typical red tomato varieties.
Cis-lycopene levels spiked around five hours after eating the
tangerine tomato sauce, and at this point during absorption the
levels were some 200 times greater than those of trans-lycopene,
which were nearly non-existent. While cis-lycopene is by far the
most abundant isomer in these tomatoes, they do contain trace
amounts of trans-lycopene.
The participants' bodies also readily absorbed beta carotene
from the beta carotene-rich tomatoes.
“Right now, only carrots and sweet potatoes are a more readily
available, richer source of beta carotene,” Schwartz said. “And
this carotenoid is a major source of vitamin A for a large
proportion of the world's population. Its deficiency is a
serious health problem in many developing countries.
“Our study showed that a tomato can also increase beta carotene
levels in the blood,” Schwartz said. While these special
tomatoes were grown just for this study, the researchers have
pre-commercial lines of both varieties available.
He conducted the study with Ohio State colleagues David Francis,
an associate professor of horticulture and crop science; Steven
Clinton, an associate professor of hematology and oncology and
human nutrition; Nuray Unlu, a former postdoctoral researcher in
food science; and Torsten Bohn, a former postdoctoral fellow in
food science at Ohio State.
Funding for this work was provided by the Ohio Agricultural and
Development Research Center in Wooster; the U.S. Department of
Agriculture's IFAFS program; the National Center of Research
Resources of the National Institutes of Health; and the National
Cancer Institute. |
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