Study challenges "carb counting" in diabetes

How many carbs you eat might be less important for your blood sugar than your food's glycemic load, a measure that also takes into account how quickly you absorb those carbs.

That's the conclusion of a new study of healthy adults, which questions the way people with type 1 diabetes determine how much insulin they should take before meals.

In type 1 diabetes, which affects about 3 million Americans, the pancreas doesn't produce sufficient amounts of the hormone insulin, which helps ferry sugar from the blood into cells. So people with the disease are quickly overwhelmed when the sugar in their food hits the bloodstream.

To avoid the dangerous blood sugar surge, diabetics inject insulin before a meal - usually based on how many carbohydrates they will be downing.

But the new study, by Jiansong Bao at the University of Sydney in Australia and colleagues, hints the number of carbs alone might not be the best way to go.

Instead, the so-called glycemic load of a food, which also takes into account how quickly it makes the blood sugar rise, might work better. Foods with soluble fiber, such as apples and rolled oats, typically have a low glycemic index, one of the contributors to glycemic load.

The researchers took finger-prick blood samples from 10 healthy young people who ate a total of 120 different types of food - all with the same calorie content. They also had two groups of volunteers eat meals with various staples from the Western diet, such as cereal, bread, eggs and steak.

The glycemic load repeatedly trumped the carb count in predicting the blood sugar and insulin rise after a meal.

"It suggests that the methods used to assess carbs in persons with type 1 diabetes might benefit from some rethinking," said Dr. Edward J. Boyko, a diabetes expert at the University of Washington in Seattle who wasn't involved in the study.

But he said it wasn't certain the findings would hold up in people who aren't completely healthy.

"In the U.S., 60 percent of people are overweight or obese so we don't know how the results would apply to them or to persons with diabetes," he told Reuters Health.

The glycemic load is calculated by multiplying the amount of carbs in grams per serving by the food's glycemic index divided by 100. The glycemic index for a variety of foods can be found at www.glycemicindex.com/.

Foods with a low glycemic index cause the blood sugar to rise slowly, and so put little pressure on the pancreas to produce insulin.

Writing in the American Journal of Clinical Nutrition, the researchers say their findings also suggest that eating foods with high glycemic loads could be linked to chronic disease like type 2 diabetes - which does not require insulin injections - and heart disease by raising blood sugar and insulin levels.