The idea that American children are being poisoned by the food industry, with the blessing of regulators, sounds like classic conspiracy theory. But when that is the stated belief of the man who may soon become America’s secretary of health, it is sensible to ask whether there is something to it. Robert F. Kennedy junior, Donald Trump’s choice for the job, wants to get rid of the entire nutrition division of the Food and Drug Administration, which he has accused of allowing toxic chemicals in foods. On that he may, or may not, have a point. The real story is that nobody knows.