FRESNO, Calif., May 15 /PRNewswire/ -- A new study appearing in the
current issue of the peer-reviewed Journal of Nutrition(1) shows that
consuming grapes protected against the destruction of insulin-producing
cells (known as beta cells) in the pancreas, significantly reducing the
incidence of diabetes in lab rodents. Naturally occurring antioxidants in
grapes known as polyphenols are believed to be responsible for this
The results of this study showed that grapes reduced the infiltration
of immune cells into the islets of Langerhans, the specific area of the
pancreas where the insulin-producing beta cells reside, thus preventing
their damaging effects on the beta cells. Grapes also reduced the levels of
an inflammatory protein in spleen cells, known as TNF-alpha.
Additionally, the researchers observed that the grape diet resulted in
a significantly higher antioxidant capacity of the blood. Higher blood
antioxidant capacity may potentially contribute to a reduction in oxidative
stress in the islets of Langerhans and form yet another layer of
protection; however, this was not directly tested. The powerful antioxidant
activity of grape polyphenols is thought to be part of the mechanism of
protection attributed to grapes.
"The protective effect of grapes was quite significant and very
exciting," said principal investigator Susan J. Zunino, Ph.D. of the USDA
Agricultural Research Service's Western Human Nutrition Research Center in
Davis, California where the study was conducted. "In this study we observed
firsthand their effect on two of three critical components for the
prevention of type I diabetes: the preservation of the beta cells and the
inhibition of inflammation. Other studies have shown that quercetin and
anthocyanins, which are phytonutrients present in grapes, enhanced insulin
secretion and sensitivity, which is the third critical component. Clearly
more studies need to be done to fully define the mechanisms of action for
the grapes and their potential as a dietary intervention for diabetes."
Leading health experts agree that to get the benefit of phytonutrients
found in foods, such as the polyphenols in grapes, it is best to consume
the whole fruit as opposed to a supplement. Fresh grapes provide an array
of natural antioxidant compounds including polyphenols, such as
resveratrol, and other biologically active compounds in their natural
environment, all of which may either contribute to the beneficial effects
or provide the optimal conditions for a certain phytonutrient to exert its
particular individual benefit.
"This study further reinforces the growing evidence that grapes have
anti- inflammatory and antioxidant properties that appear to offer
significant health benefits across a number of disease states," said
Kathleen Nave, president of the California Table Grape Commission.
In order to ensure the scientific validity of grape health studies, a
representative sample of fresh California grapes was collected and freeze-
dried into an edible grape powder which contains all of the biologically
active compounds found in fresh grapes.
The onset of Type 1 diabetes, also known as insulin dependent diabetes
mellitus (IDDM) is characterized by the infiltration of activated T
lymphocytes in to an area of the pancreas known as the islets of
Langerhans. This causes inflammation and the progressive destruction of the
body's only insulin-producing cells, the beta cells. The destruction of
these cells leads to a severe depletion of insulin, which is critical to
the body's metabolism. To survive, insulin must be delivered via injection
or pump. Type I diabetes accounts for 5-10% of all diagnosed human cases of
diabetes, according to the American Diabetes Association.
This study was supported by the United States Department of Agriculture
and the National Institutes of Health. No funding was provided by the
California Table Grape Commission. For more information go to:
(1) Journal of Nutrition, vol.137: 1216-1221, May 2007.
SOURCE California Table Grape Commission