“Most big pharma companies don’t know squat about how to reverse your diabetes,” the video says.

Mr. Huckabee, who lost more than 100 pounds after being diagnosed with Type 2 diabetes in 2003, says in the video, “Techniques just like you’re going to find in this kit worked for me.”

Asked this month at an appearance in Iowa if he had used cinnamon and chromium picolinate to reverse his diabetes, he said he had not. “No, I reversed it by taking better care of my health,” he said. Pressed about the dietary supplements promoted by the company he endorses, for which he was paid an undisclosed fee, he said: “I’ll do anything that promotes good health. Yes, sir.”

Mr. Huckabee’s spokeswoman, Alice Stewart, said his contract to promote the diabetes cure ended the first week in March. “It was something created several months ago, back in 2014, but due to possible future plans, they have concluded the relationship,” Ms. Stewart said.

Yet, as of this week, the maker of the Diabetes Solution Kit, Barton Publishing of Brandon, S.D., still prominently featured Mr. Huckabee’s endorsement on its website. Its chief executive, Joe Barton, seemed to contradict the statement that his deal with Mr. Huckabee had ended. “We are abiding by all terms set forth in the contract which is confidential in nature,” he said in an email message.

He disputed that there was a scientific consensus that cinnamon, a spice, and chromium picolinate, a mineral, were ineffective in lowering blood sugar levels associated with diabetes. “It flat-out works for people!” he wrote.

Although supplements line the shelves of pharmacies and supermarkets, scientific organizations say the evidence for their help in treating diabetes, the seventh leading cause of death in the United States, comes up short.

The American Diabetes Association advises, “Research has not been able to prove that dietary or herbal supplements (including omega-3 supplements, cinnamon and other herbs) help to manage diabetes.”