Does apple cider vinegar break a fast?
A tablespoon of apple cider vinegar does not meaningfully break a fast — it is roughly 3 calories and under 1 gram of carbohydrate. Its measured effects on insulin sensitivity are real but were demonstrated alongside meals, not during fasts. ACV gummies are a different product and do break a fast: they are sugar-based.
| Fasting for | Verdict | Why |
|---|---|---|
| Weight loss | Doesn't break it | Approximately 3 kcal per tablespoon. Immaterial to a deficit. |
| Autophagy | Depends | No protein and almost no energy. Acetate is metabolised, so it is not a categorical zero, and strict fasters skip it. |
| Blood work | Breaks it | Water only. It has documented effects on glucose handling. |
| Ketosis | Doesn't break it | A tablespoon of apple cider vinegar contains under 1 g of carbohydrate and will not interrupt ketosis. ACV gummies carry 2 to 4 g of sugar each and can. |
| Gut rest | Depends | Acidic on an empty stomach. It delays gastric emptying, which cuts both ways depending on your goal. |
Why
Acetic acid is the active component and it is metabolised to acetate, which supplies a trivial amount of energy at the doses used. The interesting part is that vinegar is not inert: a controlled study found vinegar improved insulin sensitivity to a high-carbohydrate meal in people with insulin resistance or type 2 diabetes, a randomised controlled trial in type 2 diabetes with dyslipidaemia measured effects on glycaemic indices and oxidative stress markers, and a GRADE-assessed dose-response meta-analysis of controlled trials has since synthesised the glycaemic control and insulin sensitivity evidence. Note carefully what every one of those studies did: they gave vinegar *with or before a carbohydrate meal* and measured the response to that meal. None of them studied vinegar during a fast, and none supports the popular claim that ACV enhances fat burning or "boosts" a fast. One more thing is worth knowing, because almost nobody answering this question mentions it: the 2024 trial most often cited for dramatic apple cider vinegar weight loss was retracted in 2025. Pages still quoting that result are quoting a withdrawn paper. The honest position is that a tablespoon is metabolically negligible, its documented benefits belong to mealtimes, and taking it fasted mostly forfeits the effect it is known for.
Approximately 3 kcal per tablespoon (15 ml).
The exceptions
This is usually where the real question lives.
- ACV gummies contain sugar — typically 2 to 4 g each — and break a fast. They are the fastest-growing version of this product and the one that fails.
- Undiluted vinegar erodes tooth enamel and can burn the oesophagus. Dilute it, always.
- The demonstrated benefits are meal-associated. Taking it during a fast gives up the effect you wanted.
- "With the mother" makes no difference to any of this.
- A widely-cited 2024 trial reporting large weight loss from apple cider vinegar in Lebanese adolescents was RETRACTED in 2025. Many pages answering this question still cite it as live evidence. It is listed in the sources below so you can see the retraction notice yourself.
Sources
- Vinegar improves insulin sensitivity to a high-carbohydrate meal in subjects with insulin resistance or type 2 diabetes — Diabetes Care, 2004PMID 14694010
- Vinegar Consumption Increases Insulin-Stimulated Glucose Uptake by the Forearm Muscle in Humans with Type 2 Diabetes — J Diabetes Res, 2015PMID 26064976
What it does not show: Vinegar was given with a meal, in people with type 2 diabetes. It does not show any effect of vinegar taken on its own during a fast.
- Effects of apple cider vinegar on glycemic control and insulin sensitivity in patients with type 2 diabetes: A GRADE-assessed systematic review and dose-response meta-analysis of controlled clinical trials — Front Nutr, 2025PMID 39949546
- The effect of apple vinegar consumption on glycemic indices, blood pressure, oxidative stress, and homocysteine in patients with type 2 diabetes and dyslipidemia: A randomized controlled clinical trial — Clin Nutr ESPEN, 2019PMID 31451249
- Retraction: Apple cider vinegar for weight management in lebanese adolescents and young adults with overweight and obesity: a randomised, double-blind, placebo-controlled study — BMJ Nutr Prev Health, 2025PMID 41789013
Retracted. This is a retraction notice. The 2024 trial it withdraws is still cited as live evidence by many pages answering this question.
What it does not show: A retraction notice is evidence about the literature, not about vinegar.
- FoodData Central — USDA Agricultural Research Service, 2026
No clinician reviews this site. Sources on this entry were verified by the author, who is not a doctor or a dietitian — what that means.
Last updated 2026-08-15.
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