What Drinks Won't Break Your Fast

by Rob Siabanis, M.S. Candidate, Dietetic InternNutrition
Cup of coffee in front of a sunrise

Time-restricted eating (TRE), also known as time-restricted feeding (TRF), is a form of daily fasting in which eating takes place for a limited number of hours. Usually, individuals who practice TRE daily limit their meals to an 8-12 hour window, also referred to as an eating window. The reasoning behind TRE is to align feeding and fasting with the body's innate daily rhythms. 

While the full effects of TRE in humans remain to be discovered, results from early clinical trials are more than promising. Several studies have reported that adhering to a TRE protocol for 10-12 weeks results in weight loss, improved glucose tolerance, as well as reduced cholesterol and blood pressure (1)(2). Furthermore, TRE has been associated with a reduced risk of developing several chronic diseases, including diabetes (3), breast cancer (4), and heart disease (5).

Even though the research so far points to TRE being a simple yet powerful way to improve health and wellness, many questions remain unanswered. Therefore, it is not surprising that there is confusion concerning the practical implementation of TRE in everyday life. A simple internet search to check if it's okay to drink tea during the fasting period can quickly lead one into a rabbit hole of conflicting positions, vague and unclear arguments, and uncertainty. This makes sense; most clinical trials studying TRE in humans are from 2019 onward, a relatively short time in science.

One of the most asked questions about TRE is whether certain drinks are okay to have during the fasting period or not, the concern being that they might "break" the fast. Based on the most current research available, this article will first offer some context regarding fasting and then share a list of drinks that will not break your fast.

What does it mean to break a fast?

Before we get into the list of drinks that are probably safe to drink while fasting, it is essential to understand what it means to break a fast in the first place. Depending on the definition, the list of appropriate drinks will change. Unsurprisingly, there is no clear sentiment amongst the scientific community. 

The majority defines breaking the fast as consuming any food in solid or liquid form. This definition leads us to a debate about what food is or is not. For example, black coffee is not food because it contains no or only trace amounts of calories and nutrients that the body can use to grow and function. However, some scientists have argued that some non-food items, such as coffee and non-calorie sweeteners, impact the body in various ways, negating the fast's benefits. 

For this article, we will define breaking the fast as the consumption of items that register in the body as food or may cease the beneficial biological processes that take place during a fast, even if the item is not technically food. It is vital to clarify that there is little to no research that has specifically looked at the effects of specific drinks on TRE's effectiveness. However, the scientific understanding of fasting has developed just enough in recent years to make some recommendations with measured confidence. 

What drinks will not break your fast?

Included below are the drinks that will not break your fast:

Purified Water 

Purified water is produced by processing tap or groundwater. During processing, impurities are removed, usually by reverse osmosis, and then minerals are added back into the water. Drinking purified water will not break your fast since it contains no calories or macronutrients such as protein, fat, or carbohydrates.

Spring/Mineral Water

Mineral water comes from a spring that contains various minerals, such as calcium, magnesium, and potassium. One key difference with this kind of water is that companies cannot add minerals. Spring water is also okay to drink during the fasting hours since there are no calories or nutrients that the body will need to break down and process. 

Sparkling Water

Sparkling water, also known as carbonated water, is produced by dissolving carbon dioxide (CO2) into water. Carbon dioxide is a gas and does not contain any calories, so it is safe to drink during a fast. Just keep in mind that conflicting studies show that carbonated water can increase (6) or decrease (7) feelings of hunger. This effect is not yet understood, but early findings suggest that it might have to do with the gas stimulating the digestive tract. If you feel hungry after drinking sparkling water during your fast, try switching to a different beverage and see if that helps.

Lemon-infused Water

Lemon-infused water is made by adding a few slices of lemon into still or sparkling water. According to the Nutrition Coordinating Center Food & Nutrient Database (NCCBD), two slices of lemon, the typical amount used per quart of water, contain only four calories and trace amounts of protein and carbohydrates. While lemon is technically a food, the amount used here is so tiny that, biochemically speaking, it is unlikely to impact the body's metabolism. If such amounts could break a fast, then the small amounts of toothpaste and mouthwash we inevitably swallow after brushing our teeth would also break our fast! Lemon is used instead of other delicious fruits like watermelon and strawberries because it is low in fructose, the main carbohydrate found in fruit.

Black Coffee

This is perhaps the #1 beverage people ask about when fasting. This is understandable since coffee is one of the most beloved beverages worldwide. Whether or not it breaks a fast is not crystal clear. On the one hand, black coffee only has five calories per cup, and minimal protein and fat, which are known to break one's fast and activate the body's biological clocks.

On the other hand, the much-loved caffeine in coffee has been shown in a study to affect the body's circadian rhythms, namely by shifting the biological clock forward in time (8). Notably, in that experiment, the participants took caffeine three hours before bed, so the effect might not be as strong if the coffee is consumed earlier in the day. Another concern is that the liver processes caffeine after being absorbed in the gut, potentially disrupting fasting-related processes like autophagy (9). However, the same is true for the minerals found in drinking water, such as iron, calcium, and zinc, which are absorbed, transferred, and stored in the body by various protein-dependent processes (10).

Before we hastily forbid coffee, it's essential to consider whether coffee cancels out TRE's benefits in the real world. Fortunately, three clinical trials did allow participants to consume coffee and tea. They reported that TRE still had a powerful effect on the body, improving glucose control (3), as well as reducing weight, caloric intake (11), and blood pressure (5).

In conclusion, until studies show that caffeine reduces TRE's benefits by directly comparing "caffeinated" and caffeine-free TRE, it is okay to drink coffee within reason. Keep in mind that sleep experts recommend that people avoid caffeine consumption six hours before bedtime to avoid disrupted sleep (12).

Plain Tea

Tea can be broadly divided into two categories: caffeinated and non-caffeinated. Like coffee, both kinds of tea contain very few calories and negligible glucose, protein, or fat, which can start the body's circadian clocks. Caffeinated teas, such as green and black tea, were also allowed in the clinical trials mentioned above, so as with coffee, tea does not appear to affect TRE's effectiveness. 

What about herbal tea? One short study that allowed participants to drink herbal tea but prohibited caffeinated beverages found that even after four days, participants on TRE had reduced appetite, hunger, and increased fat oxidation (13). Once again, consuming tea during TRE's fasting period does not appear to negate the fasting-related benefits. 

Conclusion

The field of circadian science has gained much traction from the scientific community and individuals that want to improve their health and wellness. One of the key benefits of TRE is its flexibility, whether that pertains to the placement of the eating and fasting windows or the beverages one can consume during the fast. Because the metabolic benefits gained from practicing TRE are so powerful, it is better to continue drinking your favorite tea and coffee to help you adhere to the protocol rather than force yourself to follow a rigid and unsustainable lifestyle. Keep in mind that long-term adherence, rather than strictness, appears to be the determining factor for success based on the current evidence.


References

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  2. Wilkinson, M. J., Manoogian, E., Zadourian, A., Lo, H., Fakhouri, S., Shoghi, A., Wang, X., Fleischer, J. G., Navlakha, S., Panda, S., & Taub, P. R. (2020). Ten-Hour Time-Restricted Eating Reduces Weight, Blood Pressure, and Atherogenic Lipids in Patients with Metabolic Syndrome. Cell metabolism, 31(1), 92–104.e5. https://doi.org/10.1016/j.cmet.2019.11.004
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  9. dePaula, J., & Farah, A. (2019). Caffeine Consumption through Coffee: Content in the Beverage, Metabolism, Health Benefits and Risks. Beverages, 5(2), 37. MDPI AG. Retrieved from http://dx.doi.org/10.3390/beverages5020037 
  10. Smith, J., Carr, T., & Gropper, S. (2016). Advanced nutrition and human metabolism (7th ed.). CENGAGE Learning Custom Publishing.
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  13. Ravussin, E., Beyl, R. A., Poggiogalle, E., Hsia, D. S., & Peterson, C. M. (2019). Early Time-Restricted Feeding Reduces Appetite and Increases Fat Oxidation But Does Not Affect Energy Expenditure in Humans. Obesity (Silver Spring, Md.), 27(8), 1244–1254. https://doi.org/10.1002/oby.22518