Does apple cider vinegar break a fast?

What's in a spoonful

Apple cider vinegar is mostly water and acetic acid. A tablespoon (15 ml) has about 3 calories ¹. Acetic acid isn't sugar or protein, the two things that raise insulin the most ³, so a spoonful in a glass of water fits a fast as well as lemon water does.

Apple cider vinegar drinks, gummies and shots are a different matter: many are sweetened, or mixed with juice or honey. Read the label before you have one during a fast.

What studies show on blood sugar

In a Swedish study, 12 healthy volunteers ate white bread with different amounts of vinegar. The more vinegar, the lower their blood sugar and insulin in the first half hour, and the fuller they felt ⁴. A review that pooled trials found the same pattern: vinegar taken with a meal lowered the rise in blood sugar and insulin afterwards ².

Notice what those studies measured: vinegar softened the body's response to food. During a fast there's no meal to soften. If you want to try it for blood sugar, take it diluted with your first meal.

Protect your teeth and throat

Vinegar is an acid. When researchers soaked slices of human tooth enamel in different vinegars for a few hours, minerals dissolved from the surface, some vinegars far more than others ⁶. That was in a dish, not a mouth, but it's a good reason not to sip vinegar neat.

Tablets aren't a safer shortcut. After a report of injury to the gullet from an apple cider vinegar tablet, researchers tested eight brands and found they varied widely in size, acidity and content, with labels that were hard to trust ⁷.

MYTH

Apple cider vinegar melts fat while you fast.

FACT

No study shows that. In the best-known trial, the difference was 1 to 2 kg over three months, and it didn't last once people stopped ⁵. Your fast does the work; vinegar is optional.

Sources

1. U.S. Department of Agriculture, Agricultural Research Service. FoodData Central: Vinegar, cider (FDC ID 173469). SR Legacy. fdc.nal.usda.gov/
2. Shishehbor F, Mansoori A, Shirani F. Vinegar consumption can attenuate postprandial glucose and insulin responses; a systematic review and meta-analysis of clinical trials. Diabetes Res Clin Pract. 2017;127:1-9. doi.org/10.1016/j.diabres.2017.01.021
3. Holt SH, Miller JC, Petocz P. An insulin index of foods: the insulin demand generated by 1000-kJ portions of common foods. Am J Clin Nutr. 1997;66(5):1264-76. doi.org/10.1093/ajcn/66.5.1264
4. Östman E, Granfeldt Y, Persson L, Björck I. Vinegar supplementation lowers glucose and insulin responses and increases satiety after a bread meal in healthy subjects. Eur J Clin Nutr. 2005;59(9):983-8. doi.org/10.1038/sj.ejcn.1602197
5. Kondo T, Kishi M, Fushimi T, et al. Vinegar intake reduces body weight, body fat mass, and serum triglyceride levels in obese Japanese subjects. Biosci Biotechnol Biochem. 2009;73(8):1837-43. doi.org/10.1271/bbb.90231
6. Willershausen I, Weyer V, Schulte D, et al. In vitro study on dental erosion caused by different vinegar varieties using an electron microprobe. Clin Lab. 2014;60(5):783-90. doi.org/10.7754/clin.lab.2013.130528
7. Hill LL, Woodruff LH, Foote JC, Barreto-Alcoba M. Esophageal injury by apple cider vinegar tablets and subsequent evaluation of products. J Am Diet Assoc. 2005;105(7):1141-4. doi.org/10.1016/j.jada.2005.04.003