|
Antioxidant-rich red wine and
tea could help regulate blood sugar levels in diabetics,
suggests a new study from the University of Massachusetts.
Red wine might inhibit the activity of alpha-glucosidase,
an enzyme responsible for triggering the absorption of
glucose by the small intestine, by almost 100 per cent,
according to the new laboratory study (in vitro) published
in the Journal of Food Biochemistry.
The researchers also note that, out of four kinds of tea
tested, black tea extracts showed the highest activity for
inhibiting the enzyme.
Importantly, the Massachusetts-based researchers report no
effect on the activity of alpha-amylase, an enzyme
responsible for starch metabolism, and an undesirable
effect observed with some medications used to control
blood sugar.
"These results provide strong evidence for further
studying the use of wine and tea to manage some stages of
type 2 diabetes using animal models and clinical studies,
and point to the importance of an antioxidant-rich diet as
part of an overall management strategy," said lead
researcher Kalidas Shetty.
"This concept is not new, but we are finding clear
cellular targets for the functions of dietary
polyphenolics. Using specific beverage combinations could
generate a whole food profile that has the potential to
manage type 2 diabetes and its complications, especially
in the early stages."
Study details
Shetty, working with Young-In Kwon and Emmanouil
Apostolidis, took four random samples of red and white
wine, and extracts from four types of tea (black, oolong,
white and green teas).
Laboratory tests focussed on the alpha-glucosidase enzyme,
already used as a target for some current drugs used to
treat type-2 diabetes, and tested the wines and tea
extracts. The same concentration was also tested for
alpha-amylase activity.
The researchers report that red wine inhibited
alpha-glucosidase by almost 100 per cent, while inhibition
of the enzyme by white wines was only about 20 per cent
when 500 microlitres were used.
A dose-dependent effect for the teas was observed, with
black tea extracts possessing the highest effect on
alpha-glucosidase inhibition (over 90 per cent at a
concentration of 200 micrograms per millilitre), followed
by white tea and oolong tea (87 and 80 per cent,
respectively, at a concentration of 200 micrograms per
millilitre).
The effects were related to the concentration of
polyphenolics, said the researchers.
"Our testing showed that red wine contains roughly ten
times more polyphenolics than white wine," said Shetty.
"Laboratory results suggest that these compounds, found in
many plant-based foods, may play a role in inhibiting
alpha-glucosidase and slowing the passage of carbohydrates
into the bloodstream."
"The major phenolic components of red wine are caffeic
acid, coumaric acid, gallic acid and quercetin, and of tea
are protocatechuic acid, caffeic acid, coumaric acid and
gallic acid," stated the researchers. "These phenolic
compounds were linked to high alpha-glucosidase inhibitory
activity," they added.
Furthermore, small or negligible effects on alpha-amylase
activity were recorded by the researchers.
Take-home message
"It is clear that some wine and tea types have high
antioxidant activity and good inhibitory profiles on
carbohydrate-modulating enzymes related to glucose
absorption in the intestine," stated the researchers.
"The potential for managing both glucose absorption and
cellular redox dysfunction for preventing postprandial
hyperglycemia linked to type 2 diabetes and hyperglycemia-induced
vascular complications leading to hypertension can be
designed in part through food systems, and provides the
basis for clinical studies."
Independent comment
Dr Victoria King, research manager at Diabetes UK, told
NutraIngredients.com: "This is an interesting study but it
only looks at a limited sample of teas and red wines. It
showed that in a 'test tube' situation some of those
beverages were able to inhibit, to varying degrees, a
protein called alpha-glucosidase, which is responsible for
triggering the take-up of glucose by the small intestine.
"It is too early to tell how this research would actually
translate into clinical benefits for people with diabetes.
We certainly wouldn't recommend that people with Type 2
diabetes increase their intake of tea and red wine to
treat their condition.
"However, eating a healthy balanced diet and taking
regular physical activity will help people with diabetes
control their blood glucose levels and reduce their risk
of serious complications such as heart disease and
stroke."
An estimated 19 million people are affected by diabetes in
the EU 25, equal to four per cent of the total population.
This figure is projected to increase to 26 million by
2030.
In the US, there are over 20 million people with diabetes,
equal to seven per cent of the population. The total costs
are thought to be as much as $132 billion, with $92
billion being direct costs from medication, according to
2002 American Diabetes Association figures.
Source: Journal of Food Biochemistry (Blackwell
Publishing)
Volume 32, Number 1, Pages 15-31,
doi:10.1111/j.1745-4514.2007.00165.x
"Inhibitory potential of wine and tea against
alpha-amylase and alpha-glucosidase for management of
hyperglycemia linked to type-2 diabetes"
Authors: Y.-I. Kwon, E. Apostolidis, K. Shetty |
