During the hearing to consider his nomination to lead the Department of Health and Human Services, Robert F. Kennedy Jr. spoke at length about issues in health and medicine, including the cause of chronic illnesses, Covid-19 and ultraprocessed foods.

Here is a running list of key health claims, fact-checked by our reporters.

Chronic Disease

Mr. Kennedy’s opening statement focused on rising chronic health conditions, saying there was a crisis in children’s health in the United States. Many experts agree — though they disagree about the causes.

Forty percent of children have a chronic health condition, and the figure is higher for adolescents when obesity is included.

Roughly one in 36 children is diagnosed with an autism spectrum disorder, according to data from the Centers for Disease Control and Prevention. One in four has an allergy or eczema, and rates of Type 2 diabetes have been rising in those 19 and under every year.

And while Type 2 diabetes rates are rising, they are still low: According to the American Diabetes Association, it occurs in 0.35 percent of Americans under the age of 20.

Who Covid-19 Affects

Senator Michael Bennet of Colorado pressed Mr. Kennedy on a statement Mr. Kennedy made in 2023 in which he suggested that the coronavirus targeted and spared certain ethnic groups.

“Covid-19 is targeted to attack Caucasians and Black people,” he said in a video from The New York Post. “The people who are most immune are Ashkenazi Jews and Chinese.”

In response to Mr. Bennet, Mr. Kennedy referred to a federally funded study from the Cleveland Clinic published early in the pandemic that tried to decipher who was most susceptible to the virus.

Scientists have said that Mr. Kennedy’s interpretation of the study widely distorted the findings in the paper. While it found genetic differences that might make one individual more susceptible to Covid than another, the differences were too rare to make any generalizations about large groups of people.

Children’s Risk From Covid

During the hearing, Mr. Kennedy also asserted that 6-year-old children “basically” have “zero” risk from Covid.

The C.D.C. has noted that children with underlying medical conditions are at higher risk from severe outcomes from Covid, as well as infants younger than six months of age.

Ultraprocessed Foods and Obesity

Early in the hearing, Mr. Kennedy singled out processed food as a driver of the obesity epidemic.

“We shouldn’t be giving 60 percent of the kids in school processed food that is making them sick,” he said.

Many public health and nutrition experts say that ultraprocessed foods — which make up an estimated 73 percent of the U.S. food supply — are probably a factor in the obesity crisis in the United States, and it would be beneficial to cut back on them.

But other researchers say that the obesity epidemic is likely a result of many entangled factors, both environmental and genetic, and that the phenomenon may have started long before there were ultraprocessed foods.

The category is also wide-ranging, and it’s not clear if all ultraprocessed foods are harmful, experts say. There may be downsides to avoiding some ultraprocessed foods, like flavored yogurts and whole wheat breads and cereals, they add, because they can provide valuable nutrients.

Lindsey Smith Taillie, an associate professor of nutrition at the U.N.C. Gillings School of Global Public Health, said that it would be “transformative” to remove ultraprocessed foods from school lunches. But, she added, schools would need more resources to prepare meals from scratch.

Medicare and Medicaid

Throughout the hearing, Mr. Kennedy struggled with the nuances of Medicaid and Medicare.

He suggested “more people would rather be on Medicare Advantage” but can’t afford it because it’s more expensive. In fact, Medicare Advantage is generally less expensive on a monthly basis for beneficiaries.

He also described Medicaid as being fully federally funded. Spending is actually split between the states and the federal government. He went on to describe the premiums and deductibles as being too high when, except in very rare cases, Medicaid enrollees do not pay either of those types of fees.

Fluoride in Water

Mr. Kennedy referenced a recent study that found an association between fluoride and I.Q. — research that he felt vindicated his earlier concerns about the dangers of fluoridated drinking water.

While the description of the study’s findings was accurate, there are notable caveats.

The study, by scientists from the federally funded National Institute of Environmental Health Sciences, was an analysis of dozens of fluoride studies, which found higher fluoride exposures were linked to lower I.Q. scores.

However, researchers cautioned that none of the studies included in the analysis were conducted in the United States, where recommended fluoridation levels in drinking water are very low. At those amounts of fluoride, evidence was too limited to draw definitive conclusions.

The C.D.C. has noted that its experts “have not found convincing scientific evidence” linking community water fluoridation with adverse health effects.