Vinegar Lowers Blood Sugar
The blood sugar–raising effect of high-carbohydrate foods may be blunted by adding vinegar to the meal or by serving the meal cold, report two new studies in the European Journal of Clinical Nutrition 2005;doi:1038/sj.ejcn.1602197 and doi:1038/sj.ejcn.1602238).
Disorders of blood sugar regulation, such as metabolic syndrome—a group of metabolic abnormalities that increase the risk of heart disease, stroke, and diabetes—may be influenced by dietary changes. The glycemic index (GI) is used to describe the blood sugar–raising effects of different foods. White flour, potatoes, sugar, and white rice have high GIs, which means they raise blood sugar levels more than foods such as beans and whole grains. Limiting the intake of high GI foods helps to keep blood sugar more stable and may also curb the appetite. This has served as the rationale behind several popular weight-loss diets, including the Zone and South Beach diets.
The GI of foods may be affected by the addition of certain acids to the food and the method of preparation and storage. For example, refrigeration increases the resistant starch content—the portion of carbohydrate that is not absorbed by the intestines—of boiled potatoes. As the resistant starch fraction of a food increases, its GI decreases. Undigested resistant starch that reaches the colon also increases the production of butyric acid by cells of the colon—a factor thought to protect against colon cancer. The new studies examined the effects of the addition of acetic acid (from vinegar) and refrigeration on the metabolic responses to different carbohydrate-rich foods.
In the first study, 12 participants ate each of the following meals at one-week intervals: white wheat bread, bread with 18 grams of vinegar, bread with 23 grams of vinegar, and bread with 28 grams of vinegar (about 6 teaspoons). The meals were preceded by a blood draw to test fasting levels of glucose and insulin. Blood samples were also taken during the two hours following the meals to assess changes in blood sugar and insulin levels in response to the varying amounts of vinegar. The participants also rated their feeling of fullness or satisfaction (satiety) after a meal.
Blood sugar levels were significantly lower at 30 and 45 minutes and satiety was significantly greater at 30, 90, and 120 minutes after the meal with the highest amount of vinegar than after the plain bread meal. In general, the higher amount of vinegar in the meal, the greater the satiety and lower the levels of blood sugar and insulin.
In the second study, 13 participants were given each of the following meals at one-week intervals: three fresh boiled potatoes, boiled potatoes that were refrigerated before serving, boiled and refrigerated potatoes with a vinaigrette sauce containing 28 grams of vinegar and 8 grams of olive oil, and white bread.
Blood samples were taken after an overnight fast and during the two hours after the meal to measure levels of glucose and insulin. The GI and insulin index, a measure of the ability of a food to increase insulin levels in the blood, were also calculated.
The GI and insulin index of the refrigerated potatoes with vinaigrette were significantly lower than the values for the freshly boiled potatoes. (A lower insulin index is desirable, as higher insulin levels may be associated with heart disease development.) The insulin index of the refrigerated potatoes was 28% lower than that of the fresh boiled potatoes. Blood sugar levels were also significantly lower at most time points following a meal of cold potatoes with vinaigrette than after eating freshly boiled potatoes.
The results of these studies suggest that adding vinegar and possibly olive oil to high-carbohydrate meals may help limit elevations in blood sugar from these foods. Refrigerating boiled potatoes is an easy way to lower the GI of this popular vegetable.
Kimberly Beauchamp, ND, earned her bachelor’s degree from the University of Rhode Island and her Doctorate of Naturopathic Medicine from Bastyr University in Kenmore, WA. She cofounded South County Naturopaths in Wakefield, RI. Dr. Beauchamp practices as a birth doula and lectures on topics including whole-foods nutrition, detoxification, and women’s health.
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