WASHINGTON - During a March 17 hearing of the House Appropriations Committee’s agriculture subcommittee, Kevin Concannon, under-secretary of agriculture for food, nutrition and consumer services, said the U.S. Department of Agriculture and the Department of Health and Human Services will grant a 30-day extension to the comment period on the Scientific Report of the 2015 Dietary Guidelines Advisory Committee. This moved the deadline for public comment on the advisory committee’s report to May 8. The original comment period was set for 45 days and would have ended April 8.

On the same day on the other end of Capitol Hill, Secretary of Agriculture Tom Vilsack, giving testimony before the Senate Appropriations Committee’s agriculture subcommittee, affirmed the U.S.D.A. and the H.H.S. will stay within their statutory limits when writing the 2015 Dietary Guidelines for Americans. The departments intend to restrict the guidelines’ scope to issues directly related to diet and nutrition, Secretary Vilsack said. The departments intend to issue the 2015 Dietary Guidelines for Americans before the end of the year.

The advisory committee, comprising 14 selected diet, health and nutrition experts, on Feb. 19 submitted its report to Secretary Vilsack and H.H.S. Secretary Sylvia Mathews Burwell. The recommendations contained within the report are nonbinding, but the U.S.D.A. and the H.H.S. will refer to the report and consider its scientific findings as the agencies draft the 2015 dietary guidelines. Those guidelines, in turn, will provide updated nutrition recommendations to Americans and will be used in structuring a variety of government nutrition programs, from school lunch programs to food allowances for U.S. military troops, for the next five years.

Some members of Congress voiced concerns that the advisory committee went beyond its mandate when, for the first time, it made recommendations related to the impact of food choices on the environment and sustainability. In particular, they took umbrage with the advisory committee’s recommended promotion of three dietary patterns that it asserted would be more health promoting and less associated with adverse impacts on the environment than the current U.S. diet.

The committee highlighted what it called the Healthy U.S.-Style Pattern, the Healthy Mediterranean-Style Pattern and the Healthy Vegetarian Pattern.

“All of these dietary patterns are aligned with lower environmental impacts and provide options that can be adopted by the U.S. population,” the committee report stated. “Current evidence shows that the average U.S. diet has a larger environmental impact in terms of increased greenhouse gas emissions, land use, water use, and energy use, compared with the above dietary patterns. This is because the current U.S. population intake of animal-based foods is higher and plant-based foods are lower, than proposed in these three dietary patterns. Of note is that no food groups need to be eliminated completely to improve sustainability outcomes over the current status.”

Those recommendations raised the ire of meat industry organizations and their supporters in Congress.

Barry Carpenter, president and chief executive officer, North American Meat Institute (NAMI), said, “As NAMI has pointed out in previous comments to the committee, the dietary guidelines committee’s charter tasked them with reviewing nutrition science, which is the field from which committee members were selected. The committee’s foray into the murky waters of sustainability is well beyond its scope and expertise. It’s akin to having a dermatologist provide recommendations about cardiac care.

“It’s notable that new research was released in late 2014 that looked at the issue of food sustainability in a new way,” Mr. Carpenter said. “Instead of analyzing the carbon footprint of similar equal amounts of different foods, researchers suggested that the total nutrition provided by those equal amounts must also be considered. Ten lbs of beef or pork provide more complete nutrition when consumed than 10 lbs of rice or broccoli.

“If our government believes Americans should factor sustainability into their choices, guidance should come from a panel of sustainability experts that understands the complexity of the issue and addresses all segments such as transportation, construction, energy management and all forms of agriculture. Total sustainability analyses were not considered by the advisory committee, whose recommendations appear to be based on personal opinions or social agendas.”

Since the release of the advisory committee’s report, several senators called on the U.S.D.A. to extend the comment period. On March 16, the chairmen and ranking members of the Senate Committee on Agriculture, Nutrition and Forestry (Senator Pat Roberts of Kansas and Senator Debbie Stabenow of Michigan) and the Senate Committee on Health, Education, Labor and Pension (Senator Lamar Alexander of Tennessee and Senator Patty Murray of Oregon) jointly requested a 30-day extension.

“This advisory committee report included recommendations that are notably different from previous guidelines, which will require additional time to develop thoughtful feedback. … An extension would be extremely beneficial to help continue the transparent process and ensure that the final report is of the utmost scientific integrity.”

Senator Jerry Moran of Kansas, chairman of the Senate Appropriations Committee’s agriculture subcommittee, said in response to the decision to extend the comment period, “I am pleased U.S.D.A. heeded our call for an extension of the comment period to make certain stakeholders have enough time to review and comment on the lengthy report. There are real questions about whether the new set of Dietary Guidelines will be based on sound nutritional science, including the extensive, peer-reviewed literature that shows lean red meat is a part of a healthy diet. U.S.D.A. and H.H.S. should also reject portions of the advisory report that delve into issues well beyond the purview or expertise of the Dietary Guidelines Advisory Committee, such as the issue of environmental sustainability.”

Representative K. Michael Conaway of Texas, chairman of the House Committee on Agriculture, said, “The 571-page report of the Dietary Guidelines Advisory Committee not only went way out of scope in dealing with non-nutritional science issues, the advisory committee potentially excluded influential scientific studies when crafting their recommendations.”