Feb. 19, 2004 -- New research shows that when it comes to type 2 diabetes, not all carbohydrates are created equal. Tufts University researchers report that eating whole-grain foods, especially fiber-rich cereals, appears to improve insulin sensitivity and lower the risk of the metabolic syndrome.
Whole-grain foods have already been found to help protect against heart disease and certain cancers, and the newly published study is one of several that indicates there is a protective role for whole grains against a constellation of major risk factors that lead to metabolic syndrome -- a risk factor for cardiovascular disease and the development of type 2 diabetes.
"I think people understand the importance of eating fruits and vegetables, but when it comes to whole grains the message has pretty much been lost," researcher Nicola M. McKeown, PhD, tells WebMD. "That is in part because consumers don't really understand what whole-grain foods are."
At Least Three Servings a Day
McKeown and colleagues examined the association between eating different types of dietary carbohydrates on a group of health conditions linked to an increase risk of type 2 diabetes and cardiovascular disease, known collectively as the metabolic syndrome.
It is estimated that the syndrome, which includes disturbed glucose metabolism, abnormal blood cholesterol, central body fat distribution, and high blood pressure, affects 20%-25% of adults in the U.S. It is also said that diet plays a role in development of the syndrome, which places individuals at risk for heart disease and type 2 diabetes.
The researchers found that greater consumption of whole-grain, cereal fiber, and diets with lower glycemic index were associated with better insulin sensitivity and were less likely to be affected by insulin resistant or the metabolic syndrome. Other sources of carbohydrates, including refined grains, appeared to neither protect against nor promote the metabolic syndrome.
Diets with a high glycemic index cause a sudden and drastic jump in blood sugar levels. With low-glycemic diets blood sugar rise more gradually. As a general rule, the same low-fat, high-fiber fare -- fruits, vegetables, and whole grains and legumes -- often advised to manage weight and help prevent diabetes and other health conditions, have a low glycemic index. Conversely, starchy and processed foods such as potatoes, breads, and cereals usually have a high glycemic index.
The investigation included 2,834 people participating in the ongoing Framingham health study. The findings are reported in the February issue of the journal Diabetes Care.
Better Eat Your Wheaties?
McKeown says most Americans eat far fewer than three servings of whole grains a day. She suggests substituting brown rice for white rice and whole-wheat pasta for regular to help up your daily intake.
But she adds that spotting whole-grain products in the grocery store is not always easy.
Breakfast cereals made from whole grains will usually say so in bold letters. Foods that contain 51% or more of whole grains by weight may also carry a government-approved message linking their consumption to a decrease in heart disease and cancer risk.
Among the commercially available cereals, good whole-grain choices include shredded wheat products, Cheerios, Wheaties, and Total.
Commercially available whole-wheat breads may be harder to identify, McKeown says, because even the most healthy sounding breads may be made from refined instead of whole grains. In other words, that 12-grain bread that sounds so good for you could be made entirely with refined flours.
"If you look at the label and don't see the words "whole" then chances are the bread is made from refined grains," McKeown says. "If you see the word "enriched" instead of "whole" that usually means the grain has been refined."
'Not All the Same'
In an editorial accompanying the study, Harvard School of Public Health nutrition researcher Frank Hu, MD, PhD, wrote that dietary guidelines continue to recommend high intakes of grain products without making a clear distinction between whole and refined grains.
He and colleague Matthias Schulze, DRPH, wrote that future dietary messages should include recommendations to eat fewer refined carbohydrates and sugars, and eat more whole-grain products and healthy sources of fats and proteins.
"Just as there are good fats and bad fats, there are good carbohydrates and bad carbohydrates," Hu tells WebMD. "Americans eat very few whole grains and very few Americans are aware that not all carbohydrates are the same."