It seems nobody likes the government to tell us what to eat.

In the face of a federal push to restrict salt in food production, the industry’s trade association has launched a pro-salt campaign that it describes as its most aggressive challenge ever to federal research.

Food industry groups have fought for decades to shape federal nutritional guidelines. In the past several months, salt advocates have taken aim at the government’s methodology, joining a chorus of doctors and dietitians who have long questioned the scientific basis of many federal dietary recommendations.

The Salt Institute is arguing that the government’s understanding of salt is entirely flawed and is requesting a clinical trial to evaluate the health effects of a low-salt diet.

“The root cause of all these problems is that the dietary guidelines are faulty,” said Lori Roman, president of the Salt Institute. “We are concerned that if the government acts further to try to force people into an unnaturally low amount of sodium that we could hurt people.”

Many doctors and scientists have long questioned the independence of the dietary guidelines process, which since the 1970s has been managed by the Department of Agriculture, the same agency charged with promoting American agriculture.

Just last week the Senate approved legislation to counter proposed limits on potatoes served in school lunchrooms after spud growers spent months lobbying the department and lawmakers.

Every five years, the Agriculture Department works with the Department of Health and Human Services to update the nutritional guidelines. A federal advisory committee is tasked with compiling a scientific report, which department employees distill into a policy paper and graphic. Health policy experts outside the government acknowledged that the deliberations of the 2010 panel were more transparent than ever, but they were wary of an anonymous eight-member independent scientific review board tasked with evaluating the final product.

Earlier this year, the Department of Agriculture replaced the long-standing food pyramid with a “my plate” image describing the suggested proportions of a meal.

“How they got from the advisory committee’s research report to the plate is a complete mystery,” said Marion Nestle, a professor of nutrition, food studies and public health at New York University who served on the 1995 dietary guidelines advisory committee. “I want to know whether those were scientific decisions or political decisions. You can’t know that unless you know who those members are.”

The Physicians Committee for Responsible Medicine filed a lawsuit earlier this year alleging that the department uses deliberately obscure language when describing foods consumers should avoid because the department has a mission to protect and promote agricultural products such as cheese and meat.

“You need to speak clearly when you write these recommendations, rather than talk in circles around the issue,” said Susan Levin, a Physicians Committee dietitian who followed the development of the guidelines. “Solid fat, for example” — which is a term in the new guidelines — “I don’t even think scientists know what that means. It’s almost like a term they came up with because they don’t want to say, ‘Don’t eat cheese.’”

The Department of Agriculture is responsible for the marketing of the guidelines, including the production of the graphic that serves as the public face of nutrition.

“The protein drives me crazy,” Nestle said, referring to an element of the “my plate” graphic. “It’s nutritionally incorrect because grains have protein and dairy has protein.”

Activist eaters are also joining the fray.

The Healthy Nation Coalition, a fledgling organization made up of dietitians, nutrition doctorates and “Paleolithic eaters” — who shun modern industrial foods — is working to extract the process from the department entirely.

Adele Hite, the group’s policy director, filed a Freedom of Information Act request for the names of the review board members. She has not heard back.

“They all come back to this idea that people need access to healthy, affordable food, but they use a definition of healthy that is based on a political process,” Hite said. “If there is no outside influence, if there are no shenanigans, if this is exactly clear and above board, then why is it such a big secret?”

Robert Post, the deputy director of the Agriculture Department’s Center for Nutrition Policy and Promotion, said the panel is made up of nutrition and health educators and often includes former advisory committee members, but he declined to reveal the names of the board members. He refuted the notion that the process was subject to outside influence and pointed to the department’s new online library of research as an example of increased transparency.

“We don’t have a need to hand out their names,” he said. “Their’s is not an influential process.”

But a 2004 memo from the Office of Management and Budget on peer review policy said that “in general, an agency conducting a peer review of a highly influential scientific assessment must ensure that the peer review process is transparent by making available to the public the written charge to the peer reviewers, the peer reviewers’ names, the peer reviewers’ report(s), and the agency’s response to the peer reviewers’ report(s).”