4. Too much cow's milk. Can the type of milk a baby is fed affect his or her type 1 diabetes risk? The "cow's milk hypothesis" says so. It holds that exposing babies to infant formula containing cow's milk in the first six months of life tinkers with their developing immune systems, which may trigger the autoimmune disease. An international, ongoing clinical trial, called TRIGR, is comparing hydrolyzed infant formula with cow's milk formula to see whether the former decreases the risk of developing type 1 diabetes in children who are considered genetically susceptible. Observational research has suggested that breast-feeding may be linked to lower rates of type 1 diabetes, according to the TRIGR study website. "When I had my daughter, who is now 14, and my wife needed to supplement with formula, I was insistent that we use hypoallergenic formula," like the hydrolyzed kind being tested in TRIGR, Hurley says. One researcher he interviewed for the book told him that using hydrolyzed formula would likely cut the rate of new diabetes cases by one fifth of current levels; others think it might just cut the rate in half.
5. Too much pollution. The "POP hypothesis" involves the theory that being exposed over time to pollutants may increase the risk of both type 1 and type 2 diabetes. But the research is more convincing for type 2 diabetes at this point, Hurley says. "There have been a bunch of epidemiologic studies, where if you lived in a county where there was a toxic waste dump, you had a higher risk of developing type 2 diabetes," he says. There have also been studies linking certain factories to a high risk of type 2 diabetes. The evidence for type 1, however, is far more elusive.
Why pollution might influence risk of diabetes is unclear. It appears to interfere with metabolism, Hurley says, and there is reason to believe it may also affect the immune system. So far, researchers have primarily done population-wide studies that have shown an association between exposure to certain compounds known as persistent organic pollutants and increased risk of developing type 2 diabetes. "For now, it's just another reason to steer clear of pollutants," Hurley says.