POUR on the tomato ketchup and pile into the pizzas鈥攊t might just save
your life. To add to the growing list of the health benefits of
lycopene鈥攖he pigment that makes tomatoes red鈥攃omes the news that it
may destroy cancers of the mouth.
A team led by Betty Schwartz, a biochemist at the Hebrew University of
Jerusalem, was exploring the anticancer properties of a range of substances that
occur naturally in food. Among other things, the researchers were looking at
pro-vitamin-A carotenoids鈥攑lant pigments that the body converts into
vitamin A, such as the carotene that makes carrots orange.
The researchers were seeing what effect these precursors would have when
added to cultures of human oral cancer cells. As a control, Schwartz decided to
use lycopene, because it too is a carotenoid, but the body does not convert it
into vitamin A. To her surprise, she found that the tumour cells given lycopene
died.
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鈥淭his adds to the increasing body of evidence that lycopene in the diet can
reduce the risk of cancer at many sites, including the breast, pancreas,
prostate and intestine,鈥� says Peter Bramley of Royal Holloway, part of the
University of London, who is trying to genetically engineer tomatoes to produce
more lycopene.
Schwartz says that the cells lining the mouth are normally linked by tiny
channels called gap junctions, which allow the cells to communicate. Healthy
cells seem to detect unhealthy neighbours and order them to self-destruct, via
the gap junctions.
Cells in oral tumours lack gap junctions. This disrupts the protective
mechanism and allows the tumour cells to proliferate unchecked. Lycopene
restores the junctions, says Schwartz. Other researchers had previously
suggested that some carotenoids affect cancer in this way.
Just how lycopene restores the gap junctions isn鈥檛 clear. There are some
indications, says Schwartz, that lycopene activates relevant genes by entering
cells and attaching to a receptor on the nuclear membrane. Other results suggest
that lycopene binds to a receptor on the cell鈥檚 surface. Both processes may well
be involved, she speculates. Bramley says: 鈥淲e now need to establish the precise
mechanism of action of lycopene not only in cancer prevention, but also its
possible role in reducing cardiovascular disease and nervous-system
颈濒濒苍别蝉蝉别蝉.鈥�
Having shown that lycopene kills oral cancer cells being grown in culture,
Schwartz now plans to test its effectiveness in people. She says that the doses
of lyco-pene she will be administering are comparable to what a person would
receive from a normal healthy diet. Other research has shown that a diet high in
fruit and vegetables also significantly reduces the risk of oral cancer.
New treatments for cancers of the mouth are needed as these tumours are
particularly aggressive and tend to be advanced by the time they are diagnosed.
Only half the people diagnosed with oral cancer live for more than five
years.
Lycopene has other benefits, too. Researchers at the University of North
Carolina showed that it reduces the risk of heart attacks. And a study at
Harvard Medical School found that eating more than two tomato products a week
reduces the risk of prostate cancer by up to 34 per cent.
Red fruits such as watermelons and guavas also contain lycopene. But the best
sources may be concentrated tomato products that also have some fat content,
such as ketchup and tomato pizza toppings, Bramley says.