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Acidic Foods

Another Way to Control Blood Glucose

By David Mendosa

Most of us know that when we eat protein, fat, or fiber our blood glucose levels won’t go up. Yet few of us are aware of other foods that will actually reduce these levels.

All you need is a little acid. But it matters a lot what type of acid.

Slowing your stomach.

Acetic acid seems to be the most effective. You don’t eat or drink acid? Actually, acetic acid is the chief acid of vinegar.

The best types to use are red or white wine vinegars. The most common vinegar, white, is cheap but somewhat harsh-tasting, so it’s not a good choice for most recipes. The other common vinegar, cider vinegar, is milder and less acidic. The less common but well-known balsamic vinegar is much sweeter and would probably be a poor choice. So too is rice vinegar, which has a sweet flavor and light acidity.

Vinegar is a key ingredient in several different dishes. Typically, it is used together with oil to dress salads and vegetables. Its presence in pickles is also noticeable.

Lemon juice is just as powerful as vinegar, Jennie Brand-Miller says. Lime juice is likely to work just as well.

A surprisingly small amount is effective. A typical vinaigrette dressing of oil and vinegar works well and can taste wonderful. Add mustard powder, garlic, and your favorite spices.

In one study the glucose response with vinegar was 31 percent lower than without it. In another study vinegar significantly reduced the glycemic index of a starchy meal from 100 to 64 (where white bread = 100).

Fermented foods also reduce blood glucose levels. The natural fermentation of starch and sugars by a yeast starter culture that produces lactic and propionic acid is what makes sourdough bread. In a third study the glycemic index of sourdough bread was 68 compared 100 for non-sourdough bread.

All these foods will help you hold your blood glucose in check. They do that by slowing the speed with which your stomach empties.

Your best bet is to include a side salad with an olive oil and vinegar or lemon dressing in as many meals as possible. Your body will thank you.

Primary References:
Liljeberg H, Bjorck I. “Delayed gastric emptying rate may explain improved glycaemia in healthy subjects to a starchy meal with added vinegar.” Eur J Clin Nutr. 1998 May;52(5):368-71.

Liljeberg HG, Lonner CH, Bjorck IM. “Sourdough fermentation or addition of organic acids or corresponding salts to bread improves nutritional properties of starch in healthy humans.” J Nutr. 1995 Jun;125(6):1503-11.

Brighenti F, Castellani G, Benini L, Casiraghi MC, Leopardi E, Crovetti R, Testolin G. “Effect of neutralized and native vinegar on blood glucose and acetate responses to a mixed meal in healthy subjects.” Eur J Clin Nutr. 1995 Apr;49(4):242-7.

Secondary Reference:
Brand-Miller, Jennie, Kaye Foster-Powell, and David Mendosa. “What is the advantage of vinegar, lemon juice, and sourdough bread?” in What Makes My Blood Glucose Go Up…and Down? New York: Marlowe & Company, 2003, p. 141-2.

This is by far the most extensive discussion of the advantage of acidic foods in the popular literature. 


Kay Schmidt suggests a similar way to reduce the blood glucose levels of some fruits and vegetables. It uses a process called lacto-fermentation, which she explains:

“I manage my insulin dependent type 2 mom, using Dr. Richard Bernstein’s philosophy of low carb. Mom misses some of her favorite foods, and I have been searching for ways to make it possible to let her enjoy some foods again.

“Recently, I learned about lacto-fermentation (pickling using whey instead of vinegar), and its health benefits. I made lacto-fermented pickled beets, apple slices, zucchini, and yellow summer squash. I then had mom eat samples—about 1/4 cup each—and checked her blood sugars every 1/2 hour for 2 hours. I could not believe the results. The pickled beets and apples did not budge mom’s sugars. Ordinarily, beets and apples will cause mom’s sugars to spike too high. I even cooked the fermented apples into an apple sauce, and this didn’t budge mom’s blood sugar. Zucchini and yellow summer squash normally has only a small effect on mom’s sugar, but the lacto-fermented samples didn’t budge her blood sugar.

“Lacto-fermentation is different than just eating acidic foods. The lacto-fermentation process actually uses carbs in the food, converts it to lactic acid, and lowers the carb content. Fermented foods are a condiment, not a side dish, and so large amounts are not eaten at a time. Despite the seemingly small serving size, the fermentation adds enzymes and nutrients. Canned, cooked, or frozen vegetables and fruits lose nutrients. Most lacto-fermented foods are still considered raw food, so enzymes and nutrients are retained, and have the added benefit of nutrients being added back in by lacto-fermentation. Pickled beets are an exception…The beets are dry baked in the oven first before pickling. Not all foods are suitable for lacto-fermentation. I tried doing fruit juice, but it was ineffective for controlling the post-prandial sugar spike.

“It is easy to lacto-ferment veggies and suitable fruits. Wash thoroughly, cut into slices or small pieces, and pack tightly into a jar or crock. If using quart jars, add 4 tbs whey, 1 tbs natural sea salt (not iodized), spices, and water—filtered or distilled (not plain tap water). Water should to be added to within an inch of the top. Jars need to be sealed tightly...just a canning lid and ring…but it doesn’t have to be put in a canner or water bath...just tightly sealed. Set in a warm place for 2-3 days, then store in a dark, cool place. It’s not uncommon for the ‘brine’ to bubble and hiss as the fermentation process continues.

“The food needs to be kept submerged in the liquid. Foods tend to float up, and the top part is no longer in the brine, which is not an ideal situation. I haven’t figured out a good way when using quart jars to prevent this from happening. I guess that’s why crocks are used…the opening is large enough to put some sort of weight on top of the food to keep it below liquid level. And, there are specially designed crocks now that have lids that create an airtight seal using water. The one drawback with this crock design, the water needs to be carefully watched so it can be replenished to maintain the airtight seal.

“Vegetables will last a long time…a year and more. Fruit should be eaten within a few months, because they can become ‘hard’ fairly easily. Lacto-fermentating of fruit juice can easily cause it to become vinegar.

“One way to obtain whey is by draining yogurt. One quart of yogurt will produce about a pint of whey, and the yogurt used should have live cultures. It takes about 24 hours for yogurt to fully drain. When the whey is drained out of yogurt, yocheese is made as a ‘by-product,’ which can be used in place of cream cheese in recipes, or eaten, flavored with Davinci syrups, or even without flavoring. I’m not necessarily advocating yogurt or yocheese for people with diabetes. With this, YMMV on how one’s blood sugar responds.

“Lacto-fermentation seems to augment the effect of the spices. People need to experiment with quantity to suit their taste buds. Also, one can use any spices in their favorite recipes when lacto-fermenting.

“Sally Fallon’s book, Nourishing Traditions, (NewTrends Publishing, 1999) is an introduction to lacto-fermentation. Other books include Klaus Kaufmann and Annelies Schoneck’s Making Sauerkraut and Pickled Vegetables at Home (Alive Books, 2002), and Sandor Ellix Katz's Wild Fermentation (Chelsea Green Publishing, 2003).”


Yogurt, kefir, and buttermilk is another group of low-carbohydrate foods where the sugar is converted to lactic acid. These foods are so important that they are a major part of one “corner” of The Four Corners Diet by Dr. Jack Goldberg, Dr. Karen O'Mara with Gretchen Becker (New York: Marlowe & Company, 2004).

Because lactic acid doesn’t raise blood glucose levels the way lactose and other sugars do, you don’t need to count all the carbohydrates on the food labels of these “probiotic foods,” they say. In fact, you can subtract 1 gram of carbohydrate for each ounce of these foods.

“Thus, for a standard 8-ounce container of plain yogurt, which usually says it has about 12 grams of carbohydrate, you need to count only 4,” the book continues. “This is not just speculation. Dr. Goldberg has actually measured the carbohydrate content in his own laboratory.”

Another Update

New research confirms that vinegar can reduce blood glucose. It may also help us lose weight. Diabetes Care just published the results of a study, “Vinegar Improves Insulin Sensitivity to a High-Carbohydrate Meal in Subjects With Insulin Resistance or Type 2 Diabetes,” by Dr. Carol Johnston and two associates in the department of nutrition at Arizona State University in Mesa, Arizona.

About one-third of the 29 volunteers in the study had been diagnosed with type 2 diabetes, another third had signs that they could become diabetic, and the rest were healthy. Dr. Johnston and her associates gave each participant 20 grams of apple cider vinegar in water and sweetener or a placebo to drink immediately before they ate a high-carbohydrate breakfast consisting of orange juice, a bagel, and butter. A week later, each volunteer came back for the opposite premeal treatment and then the same breakfast. After both meals, the researchers sampled blood from the participants.

Although all three groups in the study had better blood readings after meals begun with vinegar cocktails, those with prediabetes had the best results. Vinegar cut their blood-glucose rise in the first hour after a meal by about half, compared with readings after a placebo premeal drink. But those with diabetes were about 25 percent better.

Dr. Johnson writes me that the vinegar group in her testing lost an average of 2 pounds. “This was an unexpected finding — and is unpublished. We need to conduct a trial to examine this more closely. The purpose of the 4 week trial where we noted weight loss was to explore the effect of vinegar on blood cholesterol — we measured weight to control for this variable. There was no change in the placebo group and an average of 2 pounds weight loss in the vinegar group. It’s all so interesting.”

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