The intriguing metabolic impact of acetic acid, derived from vinegar, was first characterised in this column in July 2005. Since then, a number of scientific revelations have addressed inferences made from the earlier studies.
In a study among persons with type 2 diabetes, nondiabetic insulin resistant (NDIR), and 'normal' subjects, an artificially sweetened solution containing apple cider vinegar (20g) consumed prior to a meal produced significant improvements in post-meal blood glucose and insulin dynamics, yet only among the NDIR subjects.1 A notable, clinically significant improvement was observed among the diabetic subjects but did not achieve statistical significance.
This same group presented a study earlier this year where chronic (eight weeks of daily use) ingestion of vinegar (red raspberry; 30ml, thrice daily) was compared to a placebo drink (pure unsweetened cranberry juice; 22ml, thrice daily) among a sample of overweight to obese subjects.2 Based upon their previously unpublished findings of weight loss (approximately 1kg) among persons drinking a red raspberry vinegar (RRV) beverage daily for four weeks, compared to pure cranberry juice (CJ),3 this group sought to assess the impact upon body composition, blood lipids and whole body insulin sensitivity.2
Of the 27 subjects who were initially randomised to receive either beverage, only four and five subjects, in the RRV and CJ groups, respectively, completed the two-month intervention period. From this small sample size, no differences were noted between groups.
The findings of this group suggest that compliance with ingesting a high-dose vinegar beverage is challenging, even when it is derived from a fruit vinegar, and that weight/fat loss remains to be confirmed.
However, other studies examining the effect of vinegar ingestion underscore the promise of its influence on carbohydrate metabolism. The Swedish research group that has made seminal contributions on this topic found that co-ingestion of vinegar with white bread produced a decrement in blood insulin and glucose excursions.4
A sample of 12 young, nonoverweight, nonsmoking subjects was given four different test meals centred around a serving of white-wheat bread (50g of available carbohydrate), soaked in a serving of 18, 23 or 28g white vinegar, or the bread alone. Blood glucose and insulin, and self-scored satiety responses, were measured during the two hours following each test meal. Overall, dose-dependent reductions in glucose and insulin excursions were noted, complemented by dose-dependent increases in self-reported satiety.
Because of the lowering of the glucose and insulin response, these data suggest that vinegar/acetic acid slows down the rate of emptying from the stomach and/or decreases the rate of carbohydrate digestion. Similar findings were noted in a study with 11 young, nonoverweight subjects who followed the aforementioned protocol described in reference one.5 However, in this latter study, self-recorded food intake records for the remainder of the day (following the test meal) did not differ significantly from the meal without the vinegar beverage.
Acetic foods? These studies highlight the challenge of exploiting these data: how to create an ingestible consumer product that delivers a metabolically effective payload of acetic acid/vinegar and exhibits a high hedonic score to foster enduring compliance?
Numerous traditional foods and condiments have acetic acid as a core constituent, such as Japanese sunomono (vinegar-treated vegetables), sumeshi (vinegar-treated rice for sushi), potato salad (whose glycaemic blunting effects may be magnified by cold storing the potatoes/salad before consumption, for at least 24 hours),6 mustard, fish and chips, plus the traditional condiment of malt vinegar, and any vinegar-based dressing.
In certain Asian countries like Taiwan and Japan, fruit vinegars have emerged as a health beverage. Short-term ingestion studies with vinegar beverages suggest they are safe,7 but enduring, consumer-relevant efficacy remains to be explored.
1. Johnston CS, et al. Vinegar improves insulin sensitivity to a high-carbohydrate meal in subjects with insulin resistance or type 2 diabetes. Diabetes Care 2004; 27:281-2.
2. Gerber J, et al. Impact of daily vinegar consumption on body composition and insulin sensitivity in overweight, healthy adults. FASEB J 2006; 20:A579-A580.
3. Johnston CS. Strategies for healthy weight loss: from vitamin C to the glycemic response. J Am Coll Nutr 2005; 24:158-65.
4. Ãstman E, et al. Vinegar supplementation lowers glucose and insulin responses and increases satiety after a bread meal in healthy subjects. Eur J Clin Nutr 2005; 59:983-8.
5. Johnston CS and Buller AJ. Vinegar and peanut products as complementary foods to reduce postprandial glycemia. J Am Diet Assoc 2005; 105:1939-42.
6. Leeman M, et al. Vinegar dressing and cold storage of potatoes lowers postprandial glycaemic and insulinaemic responses in healthy subjects. Eur J Clin Nutr 2005; 59:1266-71.
7. Fushimi T, et al. Investigation of safety of drinks containing vinegar. J Urban Living Health Assoc [Japanese] 2005; 49:267-78.
Anthony Almada, MSc, is president and CSO of IMAGINutrition. Respond: [email protected]