High blood glucose levels -- even before they reach the level needed for a diagnosis of diabetes -- may signal an increased risk for cancer in women, according to a new study being published in the March issue of Diabetes Care.
The March journal also includes a study that found a link between high levels of persistent organic pollutants (POPs) in a person's bloodstream and insulin resistance, a precursor for type 2 diabetes. And a panel that has been studying pre-diabetes issued its long-awaited consensus statement on whom to test and how to treat this condition.
Women whose blood glucose levels are higher than normal, but not yet high enough for a diagnosis of diabetes, have an increased risk for several types of cancer, according to a study by researchers in Sweden. While previous studies have shown a link between type 2 diabetes and several cancers, this study finds the mechanisms that lead to cancer may be at work much earlier, as glucose levels begin to rise.
The study, funded by the World Cancer Research Fund, confirmed an association between high fasting glucose levels and pancreatic, breast, and endometrial cancers, and a two-fold increase in the risk of malignant melanoma. The study did not find an association between high glucose levels and total cancer risk in men.
Lead researcher Dr. Par Stattin, of the Department of Surgical and perioperative sciences at Umea University Hospital in Sweden, speculates that the lack of an association among men is due to the fact that prostate cancer, which is by far the most common cancer among men in this study, was inversely related to glucose levels. That is, high glucose levels were associated with a decreased risk of prostate cancer.
The researchers also found an increase in the prevalence of elevated blood glucose levels during the 13-year period in which participants were recruited, leading them to conclude that the cancer rate would likewise increase over time unless steps were taken to reduce rising glucose levels.
"A lifestyle that decreases plasma glucose levels may reduce overall cancer risk, not only among overweight or obese subjects, but most likely among subjects with normal body weight," the researchers concluded.
The American Diabetes Association advocates lifestyle changes that include moderate weight loss and increased physical activity of at least 150 minutes per week. Such changes have been shown to substantially reduce the risk of type 2 diabetes and are also beneficial in reducing the risk for heart disease.
People with high levels of persistent organic pollutants (POPs) in their blood are more likely to develop insulin resistance, a precursor for type 2 diabetes, according to a study by researchers in Korea.
Previous research by the same group found a link between POPs and type 2 diabetes. This study confirms that background exposure to some POPs, chemicals such as organochlorine pesticides and polychlorinated biphenyls (PCBs), is also associated with insulin resistance among people who do not yet have diabetes.
The researchers also found that the association between organochlorine pesticides and insulin resistance became stronger as people got fatter. However, among people who had very low concentrations of pesticides in their blood, the researchers found little association between waist size and insulin resistance.
Some studies have suggested an association between background exposure to POPs and a variety of adverse health effects in humans and wildlife. POPs can be particularly problematic because they persist for long periods of time in the environment, accumulate up the food chain, and can travel great distances through the air and water. Therefore, even people and animals that live nowhere near a place where POPs are being applied often show high levels of these chemicals in their bloodstream.
An international treaty banning a dozen of the world's most dangerous POPs has helped reduce exposures, but many harmful chemicals remain in use and even those that have been banned may linger in our environment for years to come. For example, chlordane was banned two decades ago in the United States but continues to be present at high levels in our food supply.
The researchers concluded that some POPs "may be involved in the pathogenesis of insulin resistance." They advise urgent prospective studies among those who have background exposure to POPs, which mostly comes from eating fatty animal foods. Since obesity may increase the toxicity of POPs, controlling weight could also help to reduce these impacts.
People who have pre-diabetes should undergo intensive lifestyle interventions, and possibly drug therapy, to reduce their risk of developing diabetes, as well as their long-term risk for developing diabetic complications, according to a consensus statement being published in the March issue of Diabetes Care.