Registered dietitian Carol Johnston, a professor of nutrition and an associate dean in the College of Health Solutions at Arizona State University, has been studying the effects of acetic acid, the main component of vinegar, on diabetic blood glucose levels, since 2004.

“If I was to show that vinegar slows progression to diabetes, then I would need hundreds of people and millions of dollars to do the studies, because diabetes has a lot of causes, including genetics,” Johnston said.

But studies do show acetic acid can be used as one tool in helping people lower blood sugar. A 2019 randomized clinical trial found “a 10 point decrease in fasting glucose concentrations,” Johnston said. “They used two ‘spoons’ of vinegar in a glass of water twice a day.”

In Johnston’s research, the people who benefited most from the use of vinegar were insulin-resistant, a condition called prediabetes. “In those with prediabetes, it was too good to be true,” she said. “It fell a good bit and stayed that way. It may be this is the group that could benefit the most.”

It’s not just apple cider – the antiglycemic response can be induced by any sort of vinegar: red and white wine vinegars, pomegranate vinegar or even white distilled vinegar.

“Basically, what acetic acid is doing is blocking the absorption of starch,” Johnston said. “If my study subjects eat a starch and add vinegar, blood glucose will go down. But if they drink sugar water and add vinegar, nothing happens. So if you’re having bacon and eggs, don’t bother. It only helps if you are consuming a starch.”

“If you’re taking a diabetes drug, the vinegar could amplify the effects of your meds,” she warned, “and your doctor might want to adjust your dosage.” Studies show the vinegar can reduce blood pressure, triglycerides and total cholesterol in rodents fed a high-fat, cholesterol-rich diet. But full-blown studies have not been conducted in humans.

Freeman, who serves on the American College of Cardiology’s prevention board, said there could be some benefit because of its antioxidant properties, like other heart-healthy fruits and vegetables, such as broccoli and blueberries.