TUESDAY, Feb. 10, 2004 (HealthDayNews) -- High amounts of iron stores in the blood may boost a healthy woman's odds of getting type 2 diabetes even if she has no known risk factors for developing the disease, a new study finds.
While researchers caution that more study is needed before any kind of recommendations are made, they note it is the first large-scale study to look at the potential association over time.
"This [study] provides strong evidence that high iron levels [that are still] within the normal range can predict future risk of type 2 diabetes," says study author Dr. Frank B. Hu, an associate professor of nutrition and epidemiology at the Harvard School of Public Health. The work appears in the Feb. 11 issue of the Journal of the American Medical Association.
It's long been known that type 2 diabetes is a common manifestation of an iron overload condition called hemochromatosis. In type 2 diabetes, the body doesn't make enough of the hormone insulin, which transports glucose from the blood to the cells, or doesn't use it properly.
But in the current study, researchers found an association between high iron stores in the body and type 2 diabetes in otherwise healthy women with no known diabetes risk factors, such as obesity.
The team followed more than 30,000 women who were part of the Nurse's Health Study, analyzing their blood samples during 1989 and 1990 when they were free of diagnosed diabetes and followed them over 10 years. During that decade, 698 developed diabetes. Then the researchers randomly picked 716 women from the study who were free of diabetes to serve as the control group.
Those who developed diabetes during the follow-up were heavier, more likely to have a family history of the disease, less likely to exercise and less likely to drink.
And they were more likely to have high iron levels, as measured by tests such as the concentration of ferritin, an iron-protein complex in the blood.
At the start, the average ferritin concentration of women with diabetes was higher -- 109 nanograms per milliliter of blood compared to 71.5 nanograms for the controls. "In women, a ferritin [level] higher than 200 nanograms per milliliter of blood is considered high," Hu says. Normal levels range from 12 to about 150 nanograms per milliliter.
Exactly what underlies the association is not entirely clear, Hu says. "There are several possibilities." Among them, excess iron stores can decrease insulin sensitivity and decrease insulin secretion, both of which can boost the odds of developing diabetes.
"It's too early to recommend all patients get tested for ferritin levels," Hu says. "We need more studies to confirm this result."
But if iron stores are too high, "there are very easy ways to lower body iron stores," Hu says. "For example, red meat is associated with increased ferritin levels," he says, so lowering red meat consumption could help.
Too much vitamin C can increase absorption of iron in the intestine, as can consuming more than three alcoholic drinks a day, Hu says.
The new study is interesting but the results are preliminary, says Dr. Nathaniel Clark, national vice president for clinical affairs for the American Diabetes Association. The group "is very interested in new research that finds new ways to examine risk factors for diabetes," he says. "It's interesting and will be interesting to see, with further studies, whether this research turns out to be correct."
But Clark fears a downside. "Studies like this, I am concerned, distract people." Since this finding is preliminary, people should focus on proven ways to reduce risk of getting diabetes, such as reducing excess weight, getting regular exercise, and eating a healthy, balanced diet low in saturated fat.