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Antioxidants from Black Tea
May Aid Diabetics According
To New Study
Polysaccharides
from black tea may blunt the spike
in sugar levels after a meal more
than similar compounds
from green and oolong tea, and offer potential
to manage
diabetes, says a new study.
The
black tea polysaccharides also demonstrated the greatest
activity for
scavenging free radicals, which are linked to development
of diseases
such as cancer and rheumatoid arthritis, according to new
findings
published in the Journal of Food Science.
Nutritional
science has increased interest in tea and its constituents,
especially
in recent years, with the greatest focus on the leaf's
polyphenol
content. Green tea contains between 30 and 40 per cent
of
water-extractable polyphenols, while black tea (green tea that has
been
oxidized by fermentation) contains between 3 and 10 per cent.
Oolong
tea is semi-fermented tea and is somewhere between green
and black tea.
The
new research looked at the polysaccharide content of different
types of
teas including: green, black and oolong tea, and measured
their ability
to inhibit the effects of alpha-glucosidase activity. By inhibiting
this carbohydrate hydrolyzing enzyme, it is possible to reduce the
spike in
glucose levels in the blood following a meal (postprandial
hyperglycemia).
If additional studies support the potential
effects of the polysaccharides,
it could see the black tea extracts
toward the diabetic supplements market.
In the US, there are almost 24
million people with diabetes, equal to 8 per cent
of the population.
The total costs are estimated to be as much as $174 billion,
with $116
billion being direct costs from prescription medication, according to
2005-2007 American Diabetes Association figures.
Many efforts
have been made to search for effective glucose inhibitors from
natural
materials. With these important new findings, there is enormous
potential for utilization of black tea polysaccharide in managing
diabetes.
Researchers from Tianjin University isolated three polysaccharide-rich
fractions from green, black, and oolong tea.
When
tested for their ability to inhibit alpha-glucosidase, as well as
antioxidant activities relating to hydroxyl radicals and DPPH radicals,
the black tea polysaccharides were found to produce the best results,
reported the researchers.
The differences in antioxidant
activities and glycosidase inhibitory
properties among the three
polysaccharide-rich fractions appeared to
be related to differences in
monosaccharide composition and molecular
weight distribution of the
polysaccharide.
Source: Journal of Food Science
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