Antioxidants May Reduce Harmful Complications of Diabetes
SAN FRANCISCO, CA -- Duke University Medical Center
researchers have found that the depletion of body chemicals
called antioxidants may increase the risk of complications from
the most common form of diabetes.
The scientists recommend that diabetics take antioxidant
supplements, such as vitamin C or E, to help stave off or even
forestall the hallmark complications of diabetes, including
blindness, kidney failure, amputation and even death.
Antioxidants neutralize oxygen "free radicals," highly
reactive chemicals that are the potentially destructive
byproducts of the body's process of turning food into energy.
Normally, the body produces enough antioxidants of its own to
keep the reactive oxygen from causing damage.
"We were able to show that patients with poor control of
their diabetes who were beginning to show signs of
complications had depleted their store of antioxidants," said
Duke researcher Dr. Emmanuel Opara in an interview. "Further,
we found a significant correlation between high blood-sugar
levels and depletion of antioxidants.
"It appears that this depletion is a major risk factor for
developing complications, and that antioxidant supplements
could lower this risk," he concluded.
Opara prepared the results of his studies for presentation
Sunday (April 19) at Experimental Biology `98, the annual
scientific meeting of the Federation of American Societies for
Experimental Biology (FASEB).
The researchers studied 50 similar people with Type II
diabetes -- also known as non-insulin-dependent or adult-onset
diabetes. In this form of the disease, insulin produced in the
body is unable to trigger the lowering of high blood sugar.
Type II diabetes afflicts about 90 percent of the estimated
10.7 million Americans diagnosed with the disease and the 5.4
million believed to have undiagnosed cases, according to the
Centers for Disease Control and Prevention.
Insulin is the hormone that normally regulates the level of
sugar (glucose) in the blood and is produced by cells in the
pancreas. Insulin is secreted when the level of blood glucose
rises -- as after a meal.
All diabetic patients in the study were taking only drugs
referred to as sulfonylureas, which increase the sensitivity of
receptors to insulin throughout the body. Half the patients
exhibited microalbuminuria, the excretion of tiny amounts of
protein in the urine that is considered a precursor of kidney
disease, while the other half did not.
The researchers took blood samples from all 50 patients, as
well as a control group of 20 similar people without diabetes,
and determined levels of antioxidants in their blood.
"We found that the non-diabetics' ability to defend against
damage from the oxygen free radicals was almost twice that of
those patients exhibiting microalbuminuria," Opara explained.
"And while the difference between the two diabetic groups was
not as pronounced, the difference was still statistically
significant. Also, antioxidant depletion correlated with high
blood sugar after meals only in the group with
The researchers determined antioxidant levels by a new
chemical assay developed at King's College in England that
enabled them to measure all known antioxidants in the blood and
to obtain a more global picture of the body's total antioxidant
capacity, Opara said. Other assays are only specific for
Using the newly developed assay, the scientists rated the
ability of the non-diabetics to defend against free radical
damage at 2.7, compared with 1.4 for those with
microalbuminuria and 1.7 for the diabetics without
Though the exact mechanism of action of the oxygen free
radicals is not yet clear, these findings confirm in humans
earlier animal studies of the chemicals' role in damage in
diabetes, Opara said. Previous Duke studies by Opara have shown
that vitamin E can delay the development of diabetes in obese
rats with Type II diabetes, and that the depletion of the
antioxidant glutathione caused diabetes in another rat
"The results we've been seeing in our animal studies are now
being borne out in humans,' Opara said. "I recommend that since
the body has many antioxidants, diabetics should take a number
of these agents, including vitamins C and E, and
The diabetic patients involved in the current study come
from Eygpt, and their samples were brought to Duke by E.
Abdel-Rahman, one of Opara's collaborators.