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.

Kennedy Jr. and FDA Commissioner Marty Makary said on Tuesday that the agency plans to remove petroleum-based synthetic food dyes from the U.S. food supply by revoking authorizations of some and working with industry to voluntarily remove others.

Experts have linked the dyes - which are found in dozens of foods, including cereals and candy - to neurological problems in some children.