Question: What should patients know before taking vinegar to help lower their blood sugar?
Answer : Vinegar has been used for millennia as a food, drink, medicinal, preservative, and disinfectant. Fruit juices are fermented with yeast into wine, which is further fermented by acetic acid bacteria into vinegar. Various types of vinegar are made from apples (cider vinegar), grapes (wine vinegar, balsamic vinegar), cereals such as barley (malt vinegar), sugar, and other products. Distilled vinegar (white vinegar) is made from dilute distilled alcohol.
The US Food and Drug administration requires products labelled "vinegar" to contain at least 4% acetic acid. Cider and wine vinegars contain 5% to 6% acetic acid; white vinegar ranges from 4% to 7%.
Vinegar has been used as a folk remedy for various conditions, including hypertension, weight loss, leg cramps, osteoarthritis, cancer prevention, jelly fish stings, and warts. Before the availability of pharmacologic glucose-lowering therapy, vinegar was used as a home remedy for diabetes.
Research to support the potential use of vinegar to lower blood sugar dates to 1988 when Japanese researchers showed that vinegar containing 5% acetic acid reduced insulin response in seven healthy volunteers. In 1995, research in five healthy study participants who ate lettuce salad with white vinegar (5% acetic acid) as a salad dressing ingredient and white bread showed a reduced glycemic response. Salad dressings prepared with vinegar neutralized with sodium bicarbonate or a salt solution did not significantly affect the glycemic response. Other research in small numbers of healthy subjects (N ≤ 14) also showed postprandial antihyperglycemic effects.[6-8] The proposed mechanism for this effect is delayed gastric emptying.
Two studies of patients with type 1 diabetes are available. In a study of 10 patients with type 1 diabetes and diabetic gastroparesis, ingestion of 30 mL apple cider vinegar in 200 mL of water further delayed gastric emptying. In the second study, which was a randomized controlled crossover trial published as a research letter, 10 men with type 1 diabetes drank vinegar (30 mL vinegar plus 20 mL water) or placebo (50 mL water) 5 minutes before a meal of bread, cheese, turkey ham, orange juice, butter, and a cereal bar. Rapid-acting insulin was given on the basis of each patient's insulin-to-carbohydrate ratio. Vinegar reduced blood glucose by 20% compared with placebo.
Most research on vinegar for hypoglycemic effects has focused on type 2 diabetes and prediabetes (insulin resistance). Several small studies involving eight to 16 patients have shown mixed results of the effects of vinegar on glucose in patients with prediabetes and type 2 diabetes.
In patients with type 2 diabetes controlled with metformin or diet, vinegar appears to lower postprandial glucose following a high-glycemic, but not a low-glycemic, meal. In studies of patients with type 2 diabetes or prediabetes, vinegar reduced postprandial insulin levels and increased muscle glucose intake following a meal of bread, cheese, turkey ham, orange juice, butter, and a cereal bar.Contrary to the positive results found with vinegar given before a meal, administration of vinegar before a 75-g glucose beverage did not affect blood glucose.
The limited available research suggests that vinegar taken before a meal may lower blood glucose from 20% to 33%. 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.
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.