The Democratic candidate for US Senate in Pennsylvania, John Fetterman, has fired back at Mehmet Oz, after a senior aide to the Republican said Fetterman might have avoided a serious stroke in May had he only eaten more vegetables.

“I had a stroke. I survived it,” Fetterman said. “I know politics can be nasty, but even then, I could never imagine ridiculing someone for their health challenges.”

The Democrat, currently Pennsylvania’s lieutenant governor, was responding to a statement to Insider on Tuesday by Rachel Tripp, senior communications adviser to Oz.

Responding to Fetterman’s mockery of a video in which Oz complained about the price of crudités, Tripp said: “If John Fetterman had ever eaten a vegetable in his life, then maybe he wouldn’t have had a major stroke and wouldn’t be in the position of having to lie about it constantly.”

Fetterman, 53, had a serious stroke in May. He returned to the campaign trail this month and has discussed the challenges of doing so.

Oz, 62, is a former heart surgeon who became a popular if controversial voice on daytime TV. In Senate testimony in 2014, for example, he admitted promoting diet pills that did not work.

Pennsylvania is a swing state, its Senate race seen as key to determining control of the chamber. But fivethirtyeight.com puts Fetterman more than 10 points ahead and Senate Republican leaders are widely reported to be moving spending elsewhere.

Donald Trump endorsed Oz but according to Rolling Stone now thinks his candidate is set to “fucking lose” – a remark Trump denied.

On Wednesday, Fetterman also released a letter signed by more than 100 Pennsylvania doctors who expressed “serious concern” about Oz’s candidacy.

The doctors said: “As physicians, we strongly believe in evidence-based medicine and sharing honest health information with the public.

“As a former daytime TV host, Dr Oz exploited the hopes and fears of his viewers by promoting unproven, ill-advised and at times potentially dangerous treatments. He has made clear that he will put enriching himself above all else, even in instances where people’s health is endangered.”

“Dr Oz’s record of spreading misinformation and sharing factually incorrect medical advice on The Dr Oz Show and otherwise is thoroughly researched and well documented.”

The letter cited British Medical Journal research and accused Oz of spreading misinformation about Covid-19.

It also raised the issue of abortion rights, under threat since the US supreme court overturned a key ruling but a threat successfully seized upon by Democrats in campaigns across the country.

The doctors said: “Dr Oz would … be another vote to criminalise abortion and he has refused to condemn efforts to ban abortion in Pennsylvania, endangering the lives of women and people who can become pregnant. He has even said that he opposes abortions in cases of rape or incest.”

The letter concluded with a statement of support for Fetterman.

In a tweet on Wednesday, Oz said: “As a doctor, I saved the lives of thousands of patients. As your senator, I plan to bring the power of change to Washington that Pennsylvania desperately needs.”