Eating to Keep Diabetes in Check

By PETER JARET

In Brief:
--One in four people born today are expected to develop Type 2 diabetes during their lifetimes.

--Shedding excess weight and exercising more can cut Type 2 diabetes risk by 58 percent.

--Favoring foods in their unrefined state -- brown rice and whole grains, for instance -- can help keep blood sugar levels from spiking.

--Exercise improves blood sugar control by increasing insulin sensitivity.

As rates of Type 2 diabetes continue to rise around the world, experts say we mostly have ourselves to blame. Genes certainly play a role in determining risk. But the surge of new cases of this debilitating disease is caused mostly by poor diets and lack of physical activity.

By all rights, the prescription should be simple: lose weight if you are overweight, and get more exercise.

Easy? Of course not. Experts have yet to come up with anything close to a surefire approach to help people shed pounds. And dietary recommendations to prevent or slow diabetes have often been contradictory and confusing. Nearly 30 years after the American Diabetes Association recommended a low-fat, high-carbohydrate diet to control diabetes, overturning the high-fat, low-carbohydrate approach of earlier decades, controversy still swirls around the amount and types of carbohydrates to eat.

Much of the debate focuses on the glycemic index, a measure of how carbohydrate-rich foods affect blood sugar, and whether these effects play a significant role in the progression of Type 2 diabetes. Foods high on the glycemic index, like sugared beverages, cake and white rice, are known to send blood sugar levels up sharply after a meal. Foods low on the index, like broccoli, lettuce, brown rice and whole grains, on the other hand, take longer to digest and hence keep blood sugar levels on a more even keel.

The American Diabetes Association has decided that patients should not be counseled to take the glycemic index into account when choosing foods. “Although it is clear that carbohydrates do have differing glycemic responses,” its policy statement declares, “the data reveal no clear trend in outcome benefits.”

That’s a mistake, says Dr. David Ludwig, an endocrinologist at Children’s Hospital in Boston and an associate professor at Harvard Medical School. “High-glycemic foods like refined grains raise blood sugar levels two to three times higher than unprocessed foods with a low glycemic index,” he said. When blood sugar levels spike, the body must churn out insulin to move glucose out of the bloodstream and into cells, where it is used for energy.

“If you’re eating high-glycemic foods meal after meal, snack after snack, day after day, that’s going to put a lot of stress on the system that produces insulin,” Dr. Ludwig said. “If the system is already compromised due to a family history of diabetes, those rapid swings of blood sugar could make a difference between remaining healthy or decompensating into Type 2 diabetes.”
Dr. Ludwig cites a study he conducted in which rats fed foods high on the glycemic index lost lean muscle mass, gained body fat and began to lose their ability to control blood sugar.

“A high percentage of insulin-producing cells in the high-glycemic rats were undergoing a process of destruction, disruptions in their architecture and scarring,” Dr. Ludwig said. The same thing, he suspects, happens in people.

But so far, evidence from human studies has been sketchy. In one recent Canadian study, there were no differences in blood sugar control among 162 volunteers assigned to one of three very different diets for a year: a low-carbohydrate regimen; a high-carbohydrate, low-glycemic-index diet; or foods high on the glycemic scale. Fasting glucose, a test widely used to monitor diabetes risk, actually rose in the group eating the low-glycemic foods.

A second study of 1,898 people found that risk of Type 2 diabetes was the same whether people reported eating foods high or low on the glycemic index.

“The notion that glycemic index matters makes intuitive sense,” said Dr. John M. Miles, a diabetes expert at the Mayo Clinic. “A lot of people have strong feelings on the subject. But the evidence just isn’t there.”

Dr. Xavier Pi-Sunyer, an endocrinologist and diabetes expert at St Luke’s-Roosevelt Hospital in New York, agreed. Given the new findings, “It seems unwise at this point to burden Type 2 diabetes patients with trying to pick and choose among different high- and low-glycemic-index foods,” he wrote in a recent review of the evidence.

But Dr. Thomas Wolever, a University of Toronto researcher who led the Canadian trial, noted that those who ate low-glycemic-index foods showed improvements in blood sugar control after meals, which may be a more important measure of glucose control than the fasting glucose test. They also had reductions in levels of C-reactive protein, a marker for inflammation that also appears to be linked to diabetes risk.

Low-glycemic diets may have another crucial advantage, Dr. Wolever suggested: they help some people shed pounds. “I’ve had people tell me it’s the only way they’ve been able to lose weight,” he said.

While no single diet works for everyone, losing weight may be the single most effective way to lower Type 2 diabetes risk. Evidence for that comes from a major trial sponsored by the National Institutes of Health, in which a randomly assigned group of overweight volunteers with early signs of diabetes were encouraged to lose about 7 percent of their body weight and engage in 150 minutes of moderate exercise weekly.

Over the next three years, only 5 percent of the lifestyle intervention group went on to develop diabetes each year, compared with 11 percent of volunteers in a control group. Weight loss and exercise proved more effective than a leading diabetes medication in preventing Type 2 diabetes.

“There’s no question that if we can get people to lose 5 or 10 pounds, we’ll be doing them a world of good,” Dr. Wolever said. The confounding question remains how.

Source:
http://health.nytimes.com/ref/health/healthguide/esn-diabetesdiet-ess.html
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