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.

In some studies, synthetic food dyes used in the United States have been associated with hyperactivity and behavioral effects in children.

ABC News’ Juju Chang speaks with Food and Drug Administration Commissioner Marty Makary on the FDA’s plan to remove artificial dyes from food and mass layoffs under Robert F. Kennedy Jr.