President Trump gave tentative support on Sunday for Robert F. Kennedy Jr.’s plan to remove fluoride from public drinking water across America.

“Well, I haven’t talked to him about it yet, but it sounds okay to me,” Trump told NBC News.

Trump’s comments come after Mr. Kennedy posted to X on Saturday that, “On January 20, the Trump White House will advise all U.S​. water systems to remove fluoride from public water. Fluoride is an industrial waste associated with arthritis, bone fractures, bone cancer, IQ loss, neurodevelopmental disorders, and thyroid disease.”

This policy declaration over social media caused a flurry of criticism and support. Mr. Kennedy’s opposition to fluoridated water, like his stance on vaccines, is controversial.

Mr. Kennedy made similar comments about fluoride in drinking water when he spoke with the Sun at an event at Philadelphia last month. “I think fluoride is a poison,” Mr. Kennedy said. “It causes cancers. Of course it causes your bones to deteriorate. And it causes severe IQ loss.”

Health officials at the Centers for Disease Control and Prevention disagree, calling the country’s community water fluoridation program that started in the 1940s “one of the ten great public health interventions of the 20th century.”

Fluoride strengthens the enamel in teeth and prevents cavities, according to the CDC. There is no federal mandate for water fluoridation, though some states have their own laws requiring it. Hawaii is the only state that bars fluoride from being added to public drinking water.

The movement to stop fluoridating water was once fringe, but it is gaining some traction — and Mr. Kennedy is now its public face. 

The National Toxicology Program, part of the Department of Health and Human Services, released findings in August that with “moderate confidence” higher levels of fluoride exposure “are associated with lower IQ in children.”

The study tested levels at twice the limit of fluoride levels in American water systems. Many European countries stopped fluoridating their water decades ago. Fluoride can now be found in many other sources like toothpaste.

Mr. Kennedy is promising to shake up the nation’s health and food industries if Trump wins a second term. The fluoride controversy comes as Trump and Mr. Kennedy continue to campaign together under the MAGA-MAHA banner, with Trump promising that Mr. Kennedy will “have a big role in health care” and that he will let him “go wild on health.”

“I’m going to let him go wild on the food. I’m going to let him go wild on medicines,” Trump said at his rally at Madison Square Garden.