Iron Levels Linked to Type 2 Diabetes
Study Shows Threefold Increase in Risk in Women With Highest Levels of Iron in Blood
By Salynn Boyles
WebMD Medical News Reviewed By Brunilda Nazario, MD
on Tuesday, February 10, 2004
Feb. 10, 2004 - Women with moderately high levels of iron in their blood appear to be at increased risk for type 2 diabetes. In a study involving more than 30,000 female nurses, women with the highest iron levels were three times as likely to develop the disease as women with the lowest levels.
A study investigator tells WebMD that more research is needed to determine if measuring iron in the blood can help predict diabetes risk. But he says it is not too soon for people to adopt dietary strategies designed to lower iron stores, like increasing fiber intake and decreasing red meat consumption.
The findings are published in the Feb. 11 issue of The Journal of the American Medical Association.
"Many of these dietary interventions have been advocated for years to prevent heart disease," Harvard School of Public Health diabetes researcher Frank B. Hu, MD, PhD, tells WebMD. "This is really like using one stone for two birds."
Iron Was Strongly Predictive
People with a condition known as hemochromatosis, characterized by blood iron levels that are eight to 10 times higher than normal, are at increased risk for type 2 diabetes. In this study, Hu and colleagues wanted to find out if people with normal blood iron levels were also at increased risk.
The researchers evaluated blood samples from 32,826 healthy female nurses, taken between 1989 and 1990. During the next 10 years, roughly 700 of the women developed type 2 diabetes, and their blood iron levels were compared with a similar number of study participants who did not develop the disease.
Not surprisingly, the diabetic people tended to be heavier and more sedentary and were more likely to have a family history of the disease. They also had higher plasma concentrations of the inflammation marker C-reactive protein.
According to Hu, iron levels, as measured by the protein ferritin, were as strongly predictive of future diabetes as any known risk factor other than obesity. Those who had the highest levels of blood iron had the greatest risk of developing type 2 diabetes, even after adjusting for other factors that might increase the risk of the disease. The women in the study who developed type 2 diabetes ate more red and processed meats, ate less fiber, and consumed more calories overall than the non-diabetic women.
He adds that excess iron appears to contribute to diabetes risk by prompting the formation of free radicals, which, in turn, compromise insulin sensitivity.
Other Dietary Influences?
Led by Hu and Rui Jiang, MD, who was the lead researcher for the latest study, the Harvard School of Health research team has long studied dietary influences and diabetes risk. Past research suggests that, among other things, drinking coffee and eating peanut butter may help protect against type 2 diabetes.
Hu tells WebMD that the strongest associations identified so far involve fiber, fats, and carbohydrates. Refined carbohydrates and trans fats have been implicated in increasing diabetes risk, and dietary fiber and polyunsaturated fats, like those found in nuts and canola oil, appear protective.
But American Diabetes Association spokesman Nathaniel Clark, MD, says he is concerned that proven interventions for lowering type 2 diabetes risk -- namely losing weight and exercising -- may be obscured if people get the message that it is all about what they eat.
"I would hate to have the public distracted from focusing on these things," he tells WebMD.
He points to findings from a major intervention study, which showed a dramatic reduction in diabetes incidence among high-risk obese people who lost moderate amounts of weight and began an exercise program.
"Encouraging people to eat more complex carbohydrates and watch their intake of saturated fats and trans fats is a good message overall," he says. "But we know that weight loss and exercise play a big part in reducing the risk of type 2 diabetes.
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Linda
Iron Levels Linked to Type 2 Diabetes 
