Mention "carbohydrate" in the same breath as "diabetes," and the ensuing debate resembles politics -- not left or right, but low or high, with no apparent middle ground. The debate is fueled by books that overpromise weight loss or reversal of diabetes, written by doctors or self-proclaimed gurus, and complicated by blogs laden with misleading statements.
"One can only speculate why on all the interest in avoiding carbohydrates," says Marion Franz, RD, CDE, owner of Nutrition Concepts by Franz, Inc. "Perhaps because a new approach always seems easier" and often leads to controversy, she says.
Let's sort through the clutter, sift through the research, and try to resolve the debate -- or at least come to a healthy compromise.
The Carb Constant
Many people assume that the average American eats an enormous and increasing amount of carbohydrate. They're wrong.
"Americans consume about 50 percent of their calories from carbohydrate, and the needle has not moved for years," says Joanne Slavin, Ph.D., RD, a food science and nutrition professor at the University of Minnesota in St. Paul who served on the 2010 U.S. Dietary Guidelines Advisory Committee. The Institute of Medicine and the Dietary Guidelines for Americans both recommend a meal plan that provides 45-65 percent of calories from carbohydrate.
Studies have found that people who get half or more of their calories from carbohydrate are at healthier body weights, Slavin says. People with diabetes don't eat differently, taking in about 45 percent of calories from carbohydrate, Franz says.
When you learn that carbohydrate from foods is what contributes most to the rise in glucose levels after eating, it's common sense to think that to lower your blood glucose, you cut carbs. But research shows it's not that simple.
For starters, if you've got insulin at the ready (from the pancreas or injection), you'll be able to use the glucose from the carbohydrate you eat and control after-meal glucose levels. Over the years, research in people with diabetes (PWDs) -- type 1 and 2 -- has tested the effects of diets ranging from very low to moderate to high in carbohydrate.
Recently the American Diabetes Association (ADA) conducted a systematic review of studies done in the last decade. "A major finding was that a PWD can follow an eating plan ranging from low in carbohydrate (30-40 percent) to high (greater than 65 percent) and still improve A1C and heart disease risk factors," says Madelyn Wheeler, RD, lead author of the ADA's review of Macronutrients, Food Groups, and Eating Patterns in the Management of Diabetes (Diabetes Care, February 2012). "A lot depends on other components of the diet; healthy or not-so-healthy fat, and whether or not people lose weight while on the eating plan."
Franz notes that if a person with prediabetes or type 2 diabetes needs to lose weight, eating fewer calories trumps the importance of percentage of calories from carbohydrate.
But Franz advises taking the research on very-low-carb studies with a grain of salt: Many of them had high dropout rates. Likewise, very-high-carb studies were difficult for most people to stick with.
Longer-term studies show that it's difficult for most people who eat about 45 percent of their calories from carbohydrate to make dramatic changes in their style of eating and food preferences.