WASHINGTON — The Food and Drug Administration has determined there is “very limited credible scientific evidence” for a qualified health claim about the relationship between whole grain consumption and a reduced risk of type 2 diabetes. The decision paves the way for food manufacturers to communicate that whole grains and whole grain-containing foods that meet certain nutrient requirements outlined by the F.D.A. may reduce the risk of type 2 diabetes, provided the qualified claim is appropriately worded so as not to mislead consumers.

In a 24-page letter sent to Mark Andon, Ph.D., vice-president of research, quality and innovation at ConAgra Foods, Inc., the F.D.A. said it intends to consider exercising its “enforcement discretion” for the following qualified health claims:

• “Whole grains may reduce the risk of type 2 diabetes, although the F.D.A. has concluded that there is very limited scientific evidence for this claim.”

• “Whole grains may reduce the risk of type 2 diabetes. F.D.A. has concluded that there is very limited scientific evidence for this claim.”

Omaha-based ConAgra Foods Inc., which filed the original petition with the F.D.A. in January 2012, applauded the announcement.

“We were the originator of this petition, and we’re thrilled the F.D.A. is confirming that whole grains have a positive effect on people’s health and well-being and can help reduce the risk of developing type 2 diabetes,” said Al Bolles, Ph.D., executive vice-president of research, quality and innovation at ConAgra Foods.

Dr. Andon agreed.

“For the 79 million Americans who are at risk for developing type 2 diabetes, this claim will provide easy, at-a-glance guidance for foods that can help reduce their risk,” Dr. Andon said.

In its original petition, ConAgra included an overview of scientific data from 8 qualified observational trials and 20 randomized controlled trials in the United States suggesting consumption of whole grains reduces the incidence of type 2 diabetes.

At that time, Dr. Andon said some of the studies determined consuming whole grains daily reduced glucose and/or insulin, while other studies found substituting whole grains for refined grains increased daily dietary fiber intake by 10 grams and reduced fasting blood glucose concentrations and insulin resistance.

ConAgra provided two proposed model health claims consistent with the data presented in the petition:

• “Scientific evidence suggests, but does not prove, that diets low in saturated fat and cholesterol that include three servings (48 grams) of whole grains per day may reduce the risk of diabetes mellitus type 2.”

• “Scientific evidence suggests, but does not prove, that whole grains (three servings or 48 grams per day), as part of a low saturated fat, low cholesterol diet, may reduce the risk of diabetes mellitus type 2.”

Products that would be eligible for the proposed health claim would include whole grains defined as “consisting of the intact, ground, cracked or flaked caryopsis, whose principal anatomical components — the starchy endosperm, germ and bran — are present in the same relative proportions as they exist in the intact caryopsis,” as well as “whole grain containing products.”

The F.D.A. filed ConAgra’s petition for comprehensive review on March 12, 2012, and posted the petition on the F.D.A. web site for a 60-day comment period. The agency said it received a total of 11 comments in response to the petition, with 7 in strong support, 3 against and 1 taking issue with the scientific evidence in the petition.

In its review of the total body of publicly available evidence the F.D.A. found mixed results. The agency said results from large, well-designed randomized, controlled intervention studies provided the strongest evidence for the claimed effect, regardless of existing observational studies on the same relationship. Meanwhile the majority of the intervention studies included in the F.D.A.’s evaluation did not show a significant relationship between whole grain consumption and reduced risk of type 2 diabetes.

“Based on the … findings of intervention and observational studies, F.D.A. concludes that, although a minority of credible studies suggest the existence of a link between whole grain intake and type 2 diabetes risk, the scientific evidence does not consistently show that whole grain intake reduces the risk of type 2 diabetes,” the F.D.A. said.

The F.D.A. said it also considered the evaluation of whole grains and risk of type 2 diabetes that was done as part of the development of the Dietary Guidelines for Americans 2010.

“Taking into account the D.G.A.C.’s findings and the additional studies F.D.A. reviewed, the agency concludes that the evidence supporting a risk reduction relationship, while credible, falls near the lower end of the ‘limited’ category and should be described as ‘very limited’ in food labeling to avoid misleading consumers,” the F.D.A. noted.

The F.D.A. currently has two approved health claims about whole grains that were approved in 1999 and 2003, respectively.

• “Diets rich in whole grain foods and other plant foods and low in fat, saturated fat, and cholesterol, may help reduce the risk of heart disease and certain cancers.”