The limited available research suggests that vinegar taken before a meal may lower blood glucose from 20% to 33%.[10,12] The response may depend on the type of glucose load—that is, a more pronounced response with a high-glycemic vs low-glycemic meal or glucose-containing beverage.[11,14]
Large amounts of vinegar can be irritating to the stomach and may cause nausea. Hypokalemia (theoretically through renal potassium loss that occurs with bicarbonate production from acetate in vinegar) has been reported with long-term ingestion of 250 mL of vinegar per day. Erosion of dental enamel also has been reported. Patients should limit consumption to a maximum of 1-2 tablespoons of vinegar diluted with water twice daily. Drinking through a straw may increase palatability and reduce contact with the teeth. A more palatable way to consume vinegar is to combine it with olive oil as a salad dressing.
Vinegar tablets also are available, but they may contain varying amounts of acetic acid. Patients should avoid very concentrated vinegar tablets; concentrations of nonneutralized acetic acid greater than 20% can damage the esophagus.
For patients who want to add vinegar to their daily diet, blood glucose should be checked more frequently and medication regimens may need to be adjusted accordingly. Vinegar could reduce postprandial hyperglycemia and delay gastric emptying, so the dose of preprandial, short-acting insulin may require an adjustment. In patients with insulin-dependent diabetes and gastroparesis, blood glucose must be monitored more frequently to prevent hypoglycemia.
It should be emphasized to patients that the use of vinegar should not replace healthy eating habits, exercise, or any glucose-lowering medications.\