Some have quit in frustration. The leading nutrition scientist at the N.I.H., Kevin Hall, recently resigned, saying he was being censored. Jim Jones, the chief of the F.D.A.’s food division, quit last month, saying “indiscriminate” layoffs would make it “fruitless” for him to continue.

Robert F. Kennedy Jr., the health secretary, has called the dyes “poison” and long blamed artificial additives for chronic disease and illness in the United States.