The Agriculture Department is preparing to tackle anew the question of what Americans ought to eat, with a panel of scientists that is giving some nutritionists and consumer groups waves of indigestion.

The USDA has decided to appoint a nine-member advisory committee to review comments and recommend "appropriate" changes to the government's controversial "Dietary Guidelines for Americans."

The guidelines, which call for reduced consumption of fats, cholesterol-rich foods, sugar and salt, have been under attack by the food industry since the Carter administration first issued them in February, 1980.

Five of the nine scientists who have been invited to sit on the panel have financial ties to the food industry, and three of those were involved in an earlier federal report that dismissed the notion that fat and cholesterol posed any danger to healthy Americans.

USDA officials said this week that the review panel has not been named and that it would be premature to discuss its membership. But invitations have already gone out to:

* Dr. Robert Olson of the St. Louis University School of Medicine, who has been a consultant for the American Egg Board and the National Dairy Council, among other groups.

* Dr. David Kritchevsky of the Wistar Institute, who has received funding from the American Egg Board, the National Dairy Council and the National Live Stock and Meat Board.

* Dr. Edward H. Ahrens of Rockefeller University, who testified against an earlier version of the guidelines in 1977, at the request of the meat industry, and reportedly carried the American Egg Board's standard in the controversy over the current guidelines.

* Dr. Frederick Stare of the Harvard School of Public Health, who has received retainers from the Cereal Institute and the Kellogg and Nabisco companies and has testified before Congress on behalf of the breakfast cereal and sugar industries.

* Dr. Bernard Schweigert of the University of California at Davis, a former assistant director of the American Meat Institute.

The potential panelists also include Dr. Henry Kamin of Duke University, Dr. Sanford Miller of the Food and Drug Administration, Dr. Lester Salans of the National Institutes of Health and Dr. Robert Levy of Tufts University, none of whom apparently has any connection to the food industry.

Olson and Kritchevsky served on the National Academy of Sciences' Food and Nutrition Board, which in 1980 came out with a controversial report suggesting that healthy Americans need not worry about fat and cholesterol in their diets.

Ahrens was one of three scientists who reviewed that report, which was made public shortly after the dietary guidelines appeared.

The choice of panelists, the Center for Science in the Public Interest told Agriculture Secretary John R. Block last month, "is a clear sign that USDA does not intend to objectively review those dietary recommendations."

The center would prefer that Block not tinker with the guidelines. But if he does, it suggested excluding members with ties to the food industry and providing a "semblance of balance" by including members from health and citizens groups.

Miller of the FDA yesterday characterized the guidelines as "relatively mild recommendations. They don't promise nirvana and immortality." But he said he hadn't heard anything further from the USDA about the advisory panel since he received his agency's approval to be on it.