Carol Johnston, a professor in the School of Nutrition and Health Promotion at Arizona State University has been studying vinegar and its health effects for more than a decade.
While her own research efforts have not linked vinegar ingestion to significant weight loss, a 2009 study from Japan found that swallowing two tablespoons of diluted apple cider vinegartwice a day with meals helped people lose about four pounds after 12 weeks.
Johnston says she buys the Japanese team’s findings because there’s good animal and lab research to suggest that vinegar could lead to metabolic changes that support weight loss. “There’s some evidence that the acetic acid in vinegar may turn on fat metabolism,” she explains. “It just hasn’t been examined adequately in humans, so we don’t have good evidence that it’s effective.” (Another study linked vinegar with reduced appetite—but only because swallowing the stuff made people feel nauseated.)
There’s better data to show that diluted vinegar can promote healthier blood-sugar levels.
“For those in a pre-diabetic state, you see this surge of blood glucose after a meal,” Johnston says. Even among healthy people, eating starch-heavy foods like pasta or pizza leads to a spike in blood glucose that may promote cardiovascular disease, she says. But by blocking the gut’s absorption of starchy foods, the acetic acid in vinegar appears to calm this unhealthy swell of blood sugar, Johnston’s research shows.