It's no secret that type 1 diabetes is on the rise in children. If current trends continue, new cases in kids younger than 5 could double by 2020, according to a study published last year in The Lancet. What's up for debate are the reasons for this increase. Is it environmental? Genetic? Something preventable? Scientists aren't sure just yet, but a book published in January, called Diabetes Rising: How a Rare Disease Became a Modern Pandemic, and What to Do About It (Kaplan Publishing), by freelance medical journalist Dan Hurley, explores the possibilities.
"Type 1 diabetes seems to be going up at a level of 3 percent a year in the United States," says Hurley, himself a longtime type 1 diabetes sufferer. "If we can find out what is causing that, we can prevent a lot of people from getting it." Clearly, he says, there is something going on in the environment—in the way people live—that is partly responsible. U.S. News asked Hurley, of Montclair, N.J., to discuss the leading theories scientists have for explaining why more kids are falling prey to type 1 diabetes and why more are expected to in the future. Below are 5 hypotheses he includes in the book. All of them presume that the person has some genetic tendency towards developing type 1 diabetes, Hurley says. "Think of these things—growth, sunlight, cow's milk in infancy, etc.—as fertilizers. With them, the underlying genetic risk is boosted."
1. Too big too fast. The "accelerator hypothesis" says that children who are bigger and grow faster are more likely to develop type 1 diabetes than kids who are smaller and grow more slowly. "Basically, [the] growth kind of stresses the body out," and overworks the organs, says Hurley. For kids who are genetically susceptible to type 1 diabetes, this bodily stress can essentially instigate the disease, he explains.
2. Too little sun. Might the sun—and vitamin D levels—be key to warding off type 1 diabetes? The "sunshine hypothesis" is based on data showing that countries situated closer to the equator, on average, have lower rates of type 1 diabetes, says Hurley. "It's not 100 percent consistent, but the pattern is pretty startling," he says. And past research has linked low levels of vitamin D, the so-called "sunshine vitamin," to increased risk of diabetes, he adds. "You're much more likely to develop type 1 if you live in Maine or Minnesota than if you live in southern California." But more research needs to be done to flesh out this theory.
3. Too clean. The "hygiene hypothesis" holds that our environments have become so clean that lack of exposure to certain germs and parasites may actually be harmful to us in some ways—including increasing our susceptibility to diseases like diabetes. "Most of us have left the farms that people lived on years ago, so combined with the sunshine hypothesis, it's like we've created this weird artificial world for ourselves where we're not outside, and we're sitting inside looking at a screen all day," says Hurley. While it wasn't uncommon for people to have intestinal parasites 100 years ago, today that's not the case and we may be paying for it. Those who embrace this hygiene theory believe that Helminthic therapy—ingesting intestinal parasites, worms that can be given in a dietary supplement—may prevent or help treat type 1 diabetes. Research into this therapy's effects is ongoing. "Nobody would recommend at this point that you should take an intestinal worm," Hurley says.
The pig whipworm, Trichuris suis, is considered to be one of the safest intestinal worms known, according to Hurley. "It's now being studied in people with other autoimmune diseases, [such as] multiple sclerosis and ulcerative colitis," he says. Other helminths, including Trichinella spiralis and Schistosoma mansoni, are being studied by researcher Anne Cooke, a professor of pathology at the University of Cambridge in the United Kingdom, in mice bred to develop type 1 diabetes. Cooke is using extracts of worms or their eggs, and she hopes to develop a well-defined extract that could be given as a pill to humans, Hurley says.
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.