Intermittent fasting (IF), a dietary pattern that cycles between periods of eating and fasting, has gained popularity for its potential to support metabolic health and weight management. As people seek ways to optimize their fasting window, a common question arises regarding the consumption of low-calorie additions. Apple cider vinegar (ACV) is a frequently discussed supplement due to its purported health benefits. The advice of health educators like Dr. Eric Berg, a prominent voice in the keto and fasting communities, is often sought to clarify whether this liquid can be included without interrupting the fasted state.
Dr. Berg’s Specific Recommendations on ACV
Dr. Berg explicitly states that consuming diluted apple cider vinegar during a fasting window does not break the fast. He encourages its use as a tool to support fasting goals. The reasoning centers on the negligible caloric and carbohydrate content in a typical diluted serving, which is insufficient to trigger a significant metabolic response.
A primary benefit he highlights is ACV’s ability to stabilize blood sugars, which helps to keep insulin levels low. By promoting better blood sugar management, ACV can enhance the metabolic state of fat-burning and help suppress hunger and cravings. He also suggests that its properties may support deeper fasting benefits, such as ketosis and autophagy, by reducing insulin resistance.
The Scientific Basis of ACV During Fasting
The scientific rationale supporting the use of ACV during a fast is rooted in its chemical composition, which is primarily water and acetic acid. A single tablespoon of pure ACV contains approximately 3 calories and less than 0.1 grams of carbohydrates, making the energy contribution virtually non-existent. The minimal presence of trace carbohydrates is a result of the fermentation process, which converts natural apple sugars into acetic acid.
Acetic acid, the compound responsible for vinegar’s sharp taste, is metabolized in a way that avoids stimulating a significant insulin spike. Since the goal of fasting is to keep insulin levels low, ACV’s minimal impact on this hormone makes it acceptable. Studies suggest that acetic acid may improve insulin sensitivity, an effect that complements the metabolic goals of fasting. The introduction of this acid does not trigger the hormonal response that would signal the body to exit the fat-burning state.
Clarifying What Ends a Fast
Understanding what truly constitutes “breaking a fast” is essential for those pursuing metabolic benefits like fat burning and cellular autophagy. For most intermittent fasting protocols, the fast is considered broken when a food or drink causes a significant rise in the hormone insulin. Insulin is the primary signal that tells the body to switch from a fat-burning state to a fuel-storage state.
While a strict water-only fast is technically broken by consuming anything with calories, the metabolic goal of IF is to maintain low insulin levels. The consumption of carbohydrates or proteins, which stimulate insulin release, is the main event that halts the metabolic process of ketosis and cellular clean-up. Therefore, small amounts of substances like ACV are often permitted because they have a negligible or beneficial effect on blood sugar and insulin, and do not interrupt the desired metabolic state.
Usage Guidelines for ACV During Intermittent Fasting
To ensure ACV supports, rather than hinders, a fast, proper consumption methods must be followed. The recommended dosage is typically one to two tablespoons of ACV, mixed into a large glass of water (8 to 16 ounces). This dilution is crucial, as consuming undiluted vinegar can damage tooth enamel and irritate the esophagus due to its high acidity.
It is recommended to use raw, unfiltered ACV that contains the cloudy sediment known as the “mother.” The mother is a complex of beneficial bacteria and enzymes that forms during fermentation.
Protecting Teeth and Avoiding Sweeteners
To further protect teeth, drinking the diluted mixture through a straw is suggested, followed by rinsing the mouth with plain water. Most importantly, avoid adding any form of sweetener, including sugar, honey, or artificial sweeteners, as these can trigger an insulin response and break the fast. The ACV drink can be consumed at any point during the fasting window to help manage appetite or support digestion.