The practice of fasting is resurfacing in a big way, and people across the globe are integrating this ancient method into their modern lifestyles. However, despite the mounds of evidence highlighting its benefits on health and longevity, there are still a lot of logistical questions left unanswered.

As coffee lovers and students of fasting, we wanted to explore the million dollar question: Does coffee break a fast?

The short answer? Probably not, but... It’s complicated. 

Read on to learn more about whether or not you should drink coffee during a fast.

What "Breaks a Fast"?

Before we can answer the question of whether or not coffee breaks a fast, we first have to define what "breaking a fast" actually means.

It turns out, the answer is not as black and white as you might think. Defining what breaks a fast depends on how you define fasting. Technically, if we define fasting as the complete abstinence from all food and beverages, even water would “break” a true fast. 

Practically, however, there are many different ways to fast other than strict dry fasting. These range from short-term intermittent fasting to alternate day fasting, liquid fasting (e.g. juice or bone broth), water fasting, and beyond. These different techniques provide a varying degree of benefits, and which type of fast you practice is ultimately up to you.

Most experts seem to agree that to get the most out of your fast, you should avoid consuming (more than a few) calories. But what about zero-calorie beverages or supplements? Or extremely low-calorie ‘fasts’ with bone broth or juice? When it comes to these nuanced substances, even the top fasting experts have come to different conclusions. 

  • Dr. Satchin Panda, whose research is in circadian rhythms and Time-Restricted Eating, theorizes that anything aside from water will break a fast, because the liver must metabolize it. 
  • Dr. Jason Fung, a nephrologist and diabetes expert, believes that zero-calorie beverages like coffee and tea will not break a fast because they don’t cause a blood glucose response.
  • On the other hand, Dr. Valter Longo’s research on longevity highlights the ability to still reap most of the benefits of fasting—even autophagy and cellular cleansing—while consuming a small amount of calories. As a result of his research, Longo coined the Fasting Mimicking Diet (FMD), a low-calorie, high-fat short-term eating protocol that’s been scientifically proven to mimic the benefits of fasting.

While these contradictions might seem strange or confusing, it is simply because each of these experts are utilizing fasting for different purposes and different beneficial outcomes in their practices.

Which brings us to the main point: Whether or not something ‘breaks a fast’ ultimately depends on 1) how you define fasting, and 2) what benefits you’re seeking from a fast.

While some may need to be more strict with their fast, others can get away with having a few calories because they will still get the benefits that they are seeking.

So let’s dive into the topic of conversation: Can I drink coffee while I fast?

For the purposes of simplicity, we’ll first discuss whether or not black coffee breaks a fast.

Does (Black) Coffee Break a Fast?

Although fasting is an ancestral practice, modern research on the topic is still in its infancy. The scientific literature does not yet answer with complete certainty if coffee breaks a fast, however there are many studies that show the benefits of fasting even in the presence of coffee and caffeine in general. 

Understanding the role that coffee plays during a fast is best done by examining the different goals of fasting individually.

Fasting for Body Composition

One of the most common reasons fasting has become so popular is because of its ability to dramatically impact body composition and promote fat loss. Due to its ability to suppress hunger and increase fat oxidation, coffee actually assists in mobilizing fatty acids and may enhance fat loss. Coffee has also been shown to activate the Nrf2 pathway, which is a genetic pathway that turns on over 200 genes, many of which are related to detoxification and fat loss.

  • Verdict: Black coffee probably doesn’t break a fast, and likely enhances the benefits.

Fasting for Energy and Mental Clarity

The energy and mental clarity that comes from a ketotic state during fasting is only emphasized with coffee. It’s no surprise that caffeine provides the body with an energy boost, but studies show that it also provides a cognitive boost that includes improved alertness, attention, and concentration. Due to its impact on energy levels, it is worth noting that consuming coffee late in the day will likely have a negative impact on sleep quality. Considering that sleep quality is a strong predictor of energy and mental clarity the following day, as well as overall health, we suggest consuming your coffee within the first half of the day, so that you can reap all the benefits and still achieve deep, restorative sleep.

  • Verdict: Black coffee probably doesn’t break a fast, and likely enhances the benefits.

Fasting for Gut Health

Fasting can make your gut stronger by giving it a rest from digestion, boosting its resilience against stress, increasing levels of good bacteria, and killing off harmful microbes. It’s no surprise that what we eat also influences our microbiome, and the latest science suggests that coffee, tea, and even wine might actually have a beneficial effect on your microbiome. The consumption of coffee (even decaffeinated) has been linked to a reduction in leaky gut as well as a more diverse colony of bacteria in the digestive tract. Coffee is also rich in polyphenols, which are antioxidants that act as fuel for microbes

However, if you experience any adverse effects from drinking coffee on an empty stomach, such as heartburn or acid reflux, you may want to forego the coffee during your fast (or opt for a cleaner coffee!).

  • Verdict: Black coffee probably doesn’t break a fast, unless you experience gastrointestinal issues from drinking it on an empty stomach.

Fasting for Longevity and Cellular Health

The health benefits of coffee on long-term health are well-studied and show promise for daily coffee consumers. However, is coffee safe to drink during a fast when your goal is autophagy? It seems as though the science, while lacking in definitive long-term studies on humans, may point to yes. 

A recent 2014 study conducted on mice showed that the consumption of both caffeinated and decaffeinated coffee triggered autophagy in vivo. In other words, not only does coffee likely NOT break a fast when it comes to longevity, it may even ENHANCE the anti-aging effects (probably due to the polyphenols in coffee, not the caffeine).

  • Verdict: Black coffee probably doesn’t break a fast, and likely enhances the benefits.

Fasting for Boosting the Immune System

Fasting itself is well-known to have potent beneficial effects on the immune system. But does coffee hinder these effects? 

Although caffeine is generally anti-inflammatory, its impact on the immune system can vary from person to person. The relationship between coffee and inflammation is not yet clear, but studies suggest two autoimmune disease risk genes (NAT2 and HLA) may be involved in determining if coffee is helpful or harmful when it comes to healing or aggravating autoimmunity. For this reason, people suffering from autoimmune disease are advised to initially remove coffee from their diet and then reintroduce it later on. Note that the quality of coffee plays a huge role on the impact of coffee and inflammation, which is why you should always invest in high-quality, organic coffee beans.

  • Verdict: It depends on your personal health history. If you know you experience negative effects from caffeine or coffee, or have an autoimmune disease, you might want to avoid coffee during a fast.

Fasting for Improved Insulin Sensitivity

Coffee is known to produce a small rise in blood glucose in certain individuals when consumed in a fasted state. This is due to the caffeine in coffee spiking cortisol, which triggers the liver to release stored glycogen. While it sounds negative, this temporary glucose spike can actually be useful if you time coffee consumption properly

When this glucose is released during a period where the body is active, it’s able to be burned as a quick source of energy. In someone who is sedentary and predisposed to blood sugar issues, however, a spike in glucose that is not followed by physical activity could contribute to insulin resistance. So if you’re consuming coffee pre-workout, for example, coffee would not derail (and might even improve) insulin sensitivity. If you’re drinking a coffee and then sitting at your desk all morning, you may be causing hormonal damage if you’re already susceptible to insulin resistance.

Fasting itself has been linked to improved insulin sensitivity in humans, particularly when the feeding period is kept earlier in the day. While longer term studies show beneficial effects on insulin sensitivity and diabetes prevention, the whole picture regarding caffeine and insulin sensitivity is not yet clear. Certain short-term metabolic studies showed that caffeine intake can acutely lower insulin sensitivity and increase glucose concentrations in certain people, revealing that the impact of caffeine on insulin sensitivity is indeed highly individual.

  • Verdict: Not yet clear. It likely depends on your activity levels, the timing of coffee consumption, and your personal sensitivity to insulin.

Fasting As A Spiritual Discipline

Fasting is one of the oldest rituals found in all ancient religions. Well-known examples include Lent for Christians or the season of Ramadan for Muslims, but fasting is also found in Buddhism, Judaism, Taoism, Jainism, and Hinduism traditions. 

While fasting for religious purposes is done in various ways, these disciplines and traditions are often rooted in spiritual ‘purity’ and therefore typically involve abstaining from worldly conveniences such as coffee. However, there are no studies on whether or not coffee breaks a fast in terms of spiritual purity—that is up to the individual to decide.

  • Verdict: Fasting as a spiritual discipline is a highly personal experience, and therefore it is up to the individual to determine “what breaks a fast” in this context.

Bottom Line: For most intents and purposes, black coffee does not break a fast.



Does Coffee With Other Stuff Break a Fast?

While it's a bit outrageous to think about, it's indeed a fact of life that not everyone drinks their coffee black. So we'll indulge you stranger folk with the secondary question of "does coffee with X break a fast?" next.

Coffee with Fats (Butter, MCT Oil, Heavy Cream, etc.)

Since fats are calorie-dense, including them in your coffee would technically “break a fast” in the most technical terms. 

That being said, some of the benefits of fasting are still present with fatty coffee, most notably mental clarity and energy, as fats provide the brain with fuel in the form of ketones. Weight loss may still be possible with fatty coffee, but results will vary from person to person (for some individuals, incorporating too much fat in their diet can actually lead to weight gain).

  • Verdict: Fatty coffee probably doesn’t break a fast if you’re going for mental clarity, energy, and (maybe) body composition.

Coffee with Protein Powder or Collagen

The amino acids found in protein powder and collagen upregulate growth pathways (like IGF1 and mTor), which would prevent some of the benefits of fasting, specifically autophagy. However, amino acids can support muscle maintenance, boost cognitive function, promote recovery, improve sleep, and even suppress hunger while fasting. Therefore, the benefits of adding protein or collagen to your coffee can outweigh the cons if you’re fasting for the purposes of improving energy, mental clarity, improving body composition, or trying to maintain muscle or athletic performance.

  • Verdict: Coffee with collagen likely doesn’t break a fast, unless you’re fasting for longevity/maximum autophagy benefits.

Coffee with Sugar 

Since sugar contains calories and is well-known to spike blood sugar, it’s best to leave it out of your coffee during a fasting period. Although certain natural sugars can definitely have a place in a healthy diet, they can interfere with many of the benefits of fasting, so it’s best to avoid all sources including refined sugar, coconut sugar, maple syrup, and yes, even honey.

  • Verdict: Coffee with sugar likely breaks a fast in most scenarios.

Coffee with Natural Zero-Calorie Sweeteners (Monk Fruit, Stevia, etc.)

Preliminary studies on non-nutritive low-calorie sweeteners like monk fruit and Stevia seem to indicate they have a generally low-glycemic impact, however the science is limited and conflicting. These hyper-sweet extracts may have anti-inflammatory, antioxidant, and anti-cancer properties, but more research is needed before the long-term impact of these non-nutritive low-calorie sweeteners are known. 

If you’re playing it safe during your fast, you may want to avoid adding them to your coffee until definitive research is conducted. However, small amounts will likely not hinder most of the benefits of fasting. 

  • Verdict: Coffee with small amounts of natural zero-calorie sweeteners probably won’t break a fast, but the science is still inconclusive.

Coffee with Artificial Sweeteners (Sweet n Low, Equal, Splenda, etc.)

Although artificial sweeteners snuck their way into the ‘dieting’ world as a healthy alternative to sugar not that long ago, the latest science suggests that they are actually having the opposite effect. Despite being zero-calorie, artificial sweeteners have been linked to gut dysbiosis, increasing the likelihood of metabolic disease and even insulin resistance

So although the connection between artificial sweeteners and fasting is not entirely clear, they will likely have a negative impact on essentially every benefit of fasting from weight loss and longevity. Therefore, it’s best to avoid them.

  • Verdict: Artificial sweeteners have a negative impact on just about every fasting benefit, so they should be avoided.

Coffee with Herbs and Spices

In normal doses, herbs and spices contain negligible calories, and will not interfere with any of the benefits of fasting. In fact, due to the high amounts of vitamins, minerals, and polyphenols they contain, adding herbs and spices into your coffee may even enhance the benefits of a fast (and the taste, too!).

  • Verdict: Coffee with herbs and spices will likely not break a fast.

Coffee and Fasting: How to Do It Right

Although the science is inconclusive in some areas, it's possible to infer that black coffee—for the most part—does not harm a fast, and in fact it may actually enhance certain beneficial processes that take place during fasting.

As we have explored, coffee can help:

  • Improve body composition and weight loss efforts
  • Boost energy and mental clarity
  • Benefit the microbiome
  • And even enhance longevity through boosting autophagy

It’s important to note, however, that not all coffee is created equal, and that the quality of coffee you consume has an impact on your fasting experience and overall health.

Most conventionally-grown coffee contains high levels of pesticides, mold and mycotoxins, and acrylamide—things you typically don't want in your body while you're fasting—and can often lead to jitters and an gastrointestinal distress when consumed on an empty stomach.

So if you’re going to drink coffee during your fast, you're better off drinking organic, mold-free coffee that provides pure, clean energy and high levels of polyphenols, without the jitters or upset stomach.

That's exactly why we've worked to source some of the healthiest coffee possible, Kion Coffee, to support you during your fast, and everyday thereafter!


*Fasting is not recommended for everyone. Please consult a qualified healthcare practitioner before starting a fasting practice.

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