Does a Spoonful of Vinegar Make the Sugar Go Down?

What Are the Claims About Vinegar?

Apple cider vinegar has been marketed in the United States in a variety of forms, including acetic acid, apple cider vinegar plus honey cocktail, tablets, and cider vinegar. It is also combined with supplements, botanicals, and food products. Apple cider vinegar is prepared by pulverizing apples into a slurry of juice and pulp, with yeast and sugar added to provide the acetic acid. Alone and in combination with other agents, such as grapefruit or kelp, apple cider vinegar has been purported to increase weight loss and aid in other wide-ranging conditions, such as arthritis, asthma, colitis, food poisoning, and gastrointestinal and skin problems.^[1] Anecdotal reports and folklore have suggested benefits from 2 tablespoons of apple cider vinegar in a cup of water to treat symptoms of food poisoning; reduce weight; or in combination with ginger, cayenne, and citrin, reduce high cholesterol levels.^[1,2] Scientific evidence to support these claims, however, is scant.

Several mechanisms of action are suggested for the purported medicinal properties of apple cider vinegar, including an antimicrobial effect and acidity leading to a hypoglycemic effect. Although evidence from scientific controlled trials is insufficient to demonstrate benefit for the diverse medical conditions for which apple cider vinegar has been used, sufficient preliminary evidence has emerged from recent studies in patients with diabetes to warrant further investigation.

Review of the Evidence

Medicinal vinegar administered as a vinegar solution (2800 mg daily) was compared with acetic acid pills (30 mg daily), considered a placebo, or eating a pickle daily for 12 weeks.^[3]The researchers found a reduction in postprandial glucose when vinegar was given with a carbohydrate meal in persons with type 2 diabetes or insulin resistance. A significant reduction in urine pH was found in the liquid vinegar group compared with the other 2 groups.^[4] An indication of hepatic and metabolic pathway action was found, evidenced by increased aspartate transaminase levels. This group of individuals, which already had well-controlled diabetes on medications and had mean baseline A1c of 6.3%, also demonstrated a modest reduction in A1c compared with the acetic acid pill (-0.22%) and pickle (-0.38%) groups.^[5] The study authors suggested that ingestion of vinegar at mealtimes, with a minimum dose of 2800 mg acetic acid daily, may improve glycemic control in diabetics.

A dose-response association between acetic acid intake and postprandial glucose and insulin responses measured up until 2 hours after ingestion was seen when participants were given vinegar along with 50 g of carbohydrates administered as sliced white bread.^[6] Participants also reported greater satiety with increased doses of acetic acid. Another study found reduced postprandial hyperglycemia among patients with type 2 diabetes when vinegar was added to a high- (mashed potatoes and low-fat milk) but not a low- (whole grain bread, lettuce, and low-fat cheese) glycemic-index meal.^[7] The authors of this study proposed that acetic acid reduced the rate of gastric emptying, leading to slowed carbohydrate absorption, and that this effect was already present in low-glycemic-index meals. They concluded that acetic acid may be beneficial in lowering postprandial glucose in diabetics.

A small study of obese patients (body mass index ≥ 29) with well-controlled type 2 diabetes (A1c 6.7%) examined the effect of ingesting 2 tablespoons of apple cider vinegar at bedtime. This group of patients, who had a mean diabetes duration of 4.9 years, had a reduction in next-morning fasting glucose from 4% to 6%.^[8] The effect of vinegar on fasting glucose was similar for participants with A1c < 6.3%, as was seen in those with levels between 6.8% and 7.0%.

A similar reduction in postprandial glucose was reported in a study of persons with type 1 diabetes that demonstrated that 2 tablespoons of vinegar given with a carbohydrate meal reduced the postprandial spike in glucose at and after 30 minutes.^[9]

Various possible mechanisms of action for the effect of vinegar have been proposed, including slowed gastric emptying,^[10,11] inhibition of digestive enzymes,^[10,11] and inhibition of glucose uptake by muscle.^[12]

In summary, studies on the efficacy of vinegar for glucose control in diabetes remain preliminary and have small sample sizes, but proposed mechanisms of action are available to test in the future. The dose of apple cider vinegar or vinegar used in studies is 2 tablespoons 2-3 times daily. Ingestion of 2 tablespoons of vinegar with water 3 times daily seems to be safe and has not been associated with reports of toxicity.^[1] As with any food product, however, microbial contamination has been documented.^[13,14,15] Potential harm from ingesting vinegar is restricted to case reports of hypokalemia and low bone mineral density with long-term ingestion over 6 years.^[16]Given the low risk for harm, patients who would like to consider using vinegar for glycemic control may undergo a therapeutic trial with close monitoring of postprandial and morning fasting glucose and A1c to assess potential efficacy.

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