Can you drink coffee while fasting?

Drinking coffee during fasting can have mixed effects depending on your goals with fasting. According to Dr. Satchin Panda and Dr. Rhonda Patrick:

1. Autophagy and Metabolism: The presence of caffeine, even in black coffee, may not fully preserve the state of a fast in terms of impacting autophagy or the metabolism related to fasting. Coffee contains compounds that can interfere slightly with fasting’s benefits, although the specific impact is still not definitive 1.

2. Circadian Rhythm: Coffee, especially with caffeine, can affect your circadian rhythm, similar to how exposure to light does. Therefore, its consumption could reset biological clocks, which is particularly relevant for timing in intermittent fasting 2.

3. Cancer Risk Studies: Some studies, such as the one by Ruth Patterson, have not categorized black coffee or tea as 'food' that breaks a fast. In these studies, the consumption of black coffee and tea was permitted during periods of fasting used to study cancer risk reduction 1.

4. Autophagy: Interestingly, irrespective of its caffeine content, coffee might increase autophagy due to its polyphenols. Dr. Guido Kroemer shares that coffee intake triggered protein deacylation, promoting autophagy in both caffeinated and decaffeinated forms 1.

In light of this, while drinking black coffee during a fasting period may not strictly break the fast, it might alter some of the fasting’s effects, especially concerning circadian rhythms and possibly autophagy. If maintaining a strict fast for autophagy or metabolic reasons, it might be more prudent to consume coffee during your eating window instead.