Intermittent fasting involves alternating periods of eating with periods of abstaining from caloric intake to promote various metabolic benefits. A frequent concern is whether taking necessary medications or supplements in capsule form compromises the fasted state. The gelatin shell surrounding many supplements raises questions about caloric intake and whether this small amount of material is enough to halt the beneficial metabolic processes of fasting.
Defining a Broken Fast
Fasting benefits stem from a shift in the body’s fuel source, moving away from burning glucose to utilizing stored fat for energy. This metabolic change, known as ketosis, occurs when insulin levels remain low for an extended period. The consumption of any food or drink that triggers a substantial insulin response effectively ends the fasted state. Even small amounts of protein or carbohydrates can stimulate insulin release, signaling that the fast is over.
For those fasting for metabolic health or weight loss, a common practical threshold is often cited as fewer than 50 calories. The type of calorie is the more important factor, as carbohydrates cause a rapid insulin spike, while fats have a minimal impact. If the goal is to maximize cellular cleansing, known as autophagy, the criteria are much stricter, and even minimal caloric intake or amino acids can be disruptive.
Analyzing the Gelatin Shell
Gelatin capsules are constructed from gelatin, a protein derived from the collagen found in animal connective tissue. A single empty gelatin capsule shell contains a negligible amount of calories, typically estimated to be between one and five calories. These calories come almost entirely from the protein content of the gelatin.
The primary concern with consuming protein during a fast is its ability to activate the mTOR pathway, a cellular signaling mechanism that promotes growth and cell building. Activating mTOR essentially puts a temporary stop to the process of autophagy. While the tiny amount of protein in a single capsule is unlikely to affect fat-burning or ketosis, it does introduce amino acids that could slightly impair the more sensitive autophagy process. Therefore, the shell alone generally does not break a fast for metabolic goals, but it is not compatible with a strict autophagy-focused fast.
Why Capsule Contents Matter More
The material housed inside the capsule is significantly more likely to break a fast than the gelatin shell itself. Many common supplements contain ingredients that are caloric or highly insulinogenic. Softgel capsules, for instance, often contain fat-soluble vitamins or omega-3s suspended in an oil base, and this oil contributes a substantial number of calories.
Contents like branched-chain amino acids (BCAAs) are problematic because the amino acid leucine is highly insulinogenic and directly activates the mTOR pathway. Furthermore, many powdered supplements use fillers, binders, or excipients to improve texture or shelf life. Ingredients such as maltodextrin, sugar, or fruit juice concentrates are common and will spike insulin, immediately breaking a fast.
Navigating Supplements During a Fast
Individuals who need to take supplements or medications while fasting have several options to minimize the risk of metabolic disruption. One strategy is to take supplements during the designated eating window, especially fat-soluble ones like Vitamins A, D, E, and K, as they are absorbed much better with food. For supplements that must be taken during the fasted state, looking for alternatives to gelatin is advisable.
Vegetable cellulose capsules, often labeled as “veggie caps” or HPMC (hydroxypropyl methylcellulose) capsules, are a plant-derived alternative. They contain non-digestible fiber, making them non-caloric and fasting-friendly. Another approach is to empty the contents of a powdered capsule directly into water, but this only works if the contents themselves are non-caloric and non-insulinogenic. The most important action is to scrutinize the ingredient list for hidden sugars, maltodextrin, or other caloric fillers that are the actual fast-breakers.