The guidelines that inform federal agencies about ideal diets for Americans should focus on nutrition, not sustainability and tax issues, Health and Human Services Secretary Sylvia Burwell and USDA Secretary Tom Vilsack told House Ag Committee members in a hearing Wednesday.

Related: Dietary guidelines' sustainability suggestion back in focus

The guidelines are crafted in part by public comment, USDA and HHS nutrition specialists and a panel of scientists that make up the Dietary Guidelines Advisory Committee.

USDA Secretary Tom Vilsack, left, and Secretary of Health and Human Services Sylvia Burwell testify during a hearing before the House Agriculture Committee October 7, 2015, on Capitol Hill in Washington, D.C. (Photo by Alex Wong/Getty Images)

The Committee's report, which was returned to the agencies in February, grabbed the attention of farm groups and other stakeholders for its comments on sustainability as it relates to the type of food Americans eat, as well as discussion of tax issues and recommendations on lean red meat.

Earlier this year, House Ag Committee Chairman Mike Conaway, R-Texas, sent a letter with additional signatories to Vilsack and Burwell raising concerns about the issues, which also were discussed in greater depth during Wednesday's hearing.

"Consumers should be able to trust the science behind DGA without fear of political or personal bias influencing each recommendation," Conaway said in comments following the discussion. "After hearing the secretaries acknowledge concern with regard to the DGAC exceeding their scope, I believe we can work together to get back on track and instill confidence in the process."

Burwell testified that while the issues raised in the committee's report are "both important," she agreed they don't belong in the context of the final DGA document, which is set to be released in December.

Several lawmakers also questioned the secretaries on the science behind the final guidelines, as they impact school lunch standards and federal nutrition efforts like the Supplemental Nutrition Assistance Program.

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Citing cholesterol from eggs – which was discouraged in prior guidelines documents, but has since been changed – some lawmakers said the agencies should be extra careful not to discourage a whole food category if it's not warranted, since it could alter how the product is perceived later on.

While Burwell conceded that such a situation did occur with cholesterol, the guidelines have been "relatively consistent" since the 1980s she said, and "the dominant picture is a very similar picture over the periods of time."

While the secretaries said consumers should be reminded that the guidelines are just that – guidelines –Conaway said they eventually become the "law of the land in many instances" because they get woven into SNAP and school lunches.

Consumption of lean red meat also has been an issue with livestock and farm groups since reviewing the committee's report in February, and made the list of talking points Wednesday.

Related: Senators say lean red meat belongs in dietary guidelines

In the report, the committee suggests that a healthy diet should be "higher in vegetables, fruits, whole grains, low- or non-fat dairy, seafood, legumes, and 116 nuts; moderate in alcohol (among adults); lower in red and processed meat; and low in sugar- sweetened foods and drinks and refined grains."

A footnote in the document said "lean meats can be part of a healthy dietary pattern" as demonstrated in the food pattern modeling of the Healthy U.S.-style and Healthy Mediterranean-style patterns.

In a March response letter, Senators said the report's suggestion to decrease consumption of red and processed meats "ignores the peer-reviewed and published scientific evidence that shows the role of lean red meats as part of a healthy diet."

Rep. Mike Rogers, R-Ala., questioned the secretaries' final opinions on that recommendation.

"I think it's fairly clear that there's a recognition that lean meat is and should be part of a healthy diet," Vilsack responded, noting that many Americans are simply consuming more calories than required.

"The [less lean meat] recommendation is in relationship to the overall consumption of calories," he said, "and one way to reduce the overall consumption of calories is obviously to eat less of certain things."

View the archived webcast on the 2015 Dietary Guidelines for Americans online.