Many of us brew coffee to begin the day. This daily ritual is said to help boost brain function, raise energy levels, and offer us motivation to tackle the day.
And yet, it seems like few things in the diet and nutrition world are more controversial than coffee. Conflicting online information says it’s extremely harmful to your health one week, and it’s reducing your risk of cancer the next.
As usual, the truth lies somewhere in the middle of these two extremes. High-quality scientific research supports that coffee seems to be neutral to beneficial for most people’s health. But there are nuances to this on an individual basis, especially when someone is more sensitive to caffeine or has a compromised gut.
In this article, we’ll discuss how coffee is processed and the potential benefits of black coffee for the liver, brain, gut, and more. We’ll also address the possible side effects from consuming coffee and a few other concerns around gluten and mycotoxins in coffee.
Let’s start from the beginning: the coffee bean.
A Closer Look at the Coffee Bean
The coffee production process begins with a fruit called a coffee cherry. Seeds from the coffee cherry are harvested and roasted to become what we know as coffee beans. Two popular types of coffee beans are Arabica and robusta — Arabica produces a more mild coffee while robusta is earthier and more bitter.
Caffeine is present in both types of beans, and we typically connect this stimulant with black coffee consumption. But giving you extra energy to start your day isn’t coffee’s only benefit. Coffee also contains a few other key nutrients, such as :
- Vitamin B2 (riboflavin)
- Vitamin B3 (niacin)
Coffee doesn’t contain significant amounts of these nutrients, but those who drink several cups of coffee daily may receive a larger daily intake.
Antioxidants in Coffee
Coffee contains several antioxidants in the polyphenol family, including caffeic acid, chlorogenic acid, and ferulic acid, all of which are very beneficial for human health .
The antioxidants in coffee may not be as well known as those in foods like green tea or berries, but they still offer protection against inflammation and developing chronic disease. Chlorogenic acid in coffee may even help us generate new nerve cells (neurons) .
For many Americans who don’t prioritize or can’t easily access fresh produce, coffee may be their greatest source of daily antioxidants.
Health Benefits of Black Coffee
Fortunately, the worldwide human obsession with coffee has given us many high-quality systematic reviews and meta-analyses on the benefits of black coffee. These analyses give us synthesized data of multiple studies at once, allowing us to find commonalities and patterns on a larger scale (and dismiss low-quality evidence).
Still, these studies are mostly population-based observational studies that only tell us about associations between coffee consumption and health rather than cause and effect. And we always want to keep in mind that drinking coffee should be included as part of an overall healthy diet and lifestyle — coffee isn’t a panacea or a miraculous elixir.
That disclaimer made, these large-scale studies found the following potential benefits of black coffee:
Coffee and Longevity
An umbrella meta-analysis found that consuming 2 to 4 cups of black coffee per day was associated with a significantly lower risk of all cause mortality.
Coffee and Cardiovascular Health
With regards to heart disease specifically, moderate coffee consumption (3-5 cups per day) was found to lower risk. However, over six cups per day was not associated with any change in risk for heart disease .
A minimum of three cups per day was associated with a small decrease (3%) in risk for high blood pressure .
However, another umbrella meta-analysis showed inconclusive evidence that coffee was associated with higher blood pressure (due to caffeine intake) and cholesterol .
Both caffeinated and decaffeinated coffee drinkers showed reduced risk of type 2 diabetes by 6% with each additional cup per day. Dose-response studies showed that the lowest risks for diabetes were associated with about 4-5 cups of coffee per day [3, 8].
Coffee and Brain Health
One umbrella meta-analysis found a reduced risk of Parkinson’s disease with moderate coffee consumption. The lowest risk was associated with between 4-5 cups of coffee per day .
At the same consumption, coffee was also associated with protection against Alzheimer’s disease. However, another systematic review found no significant relationship between coffee drinking and a lower risk of Alzheimer’s or dementia [3, 9, 10].
Coffee and Liver Health
A combination of umbrella meta-analyses and systematic review and meta-analyses found that coffee consumption was significantly associated with reduced risk of liver cancer. Heavy coffee drinkers reduced their risk of developing liver cirrhosis by 50% compared to those who did not drink coffee at all.
Coffee drinkers also lowered their risk of non-alcoholic fatty liver disease (NAFLD) by 29% compared to non-coffee drinkers. And patients who already had NAFLD and drank coffee had a 30% lower risk of developing liver fibrosis [11, 12, 13, 14].
Is Coffee Good for Your Gut Health?
We don’t have quite as much scientific evidence connecting coffee and gut health, but there are some promising studies suggesting that regularly consuming coffee can help improve the composition and diversity of your gut microbiome. However, these studies were conducted on animals and in laboratory environments, so they may not exactly translate to humans [15, 16, 17].
You should always pay attention to your body’s response to coffee and make a judgement from there on whether it’s right for you, especially if you have a sensitive digestive system.
For example, research is mixed on the effects of coffee on those with heartburn or GERD. One Japanese study suggested no link between coffee consumption and risk for these conditions , but additional research points to an increased risk of reflux with regular coffee consumption for those who are prone to the condition [19, 20].
Coffee might not be the best idea for those with diarrhea-predominant IBS (IBS-D) either, since it is known to stimulate gut motility. In other situations, this is an advantage, such as for temporary constipation after surgery . But for people with overactive GI systems, it’s not so great.
One study showed that caffeinated coffee stimulated colonic motility similar to consuming a meal, and its effects were 23% stronger than decaf coffee and 60% stronger than water .
If you’re working on improving your gut health, it may be helpful to cut back on or avoid coffee for a while. But there’s no reason that you have to cut it out completely or feel deprived if you enjoy drinking coffee. Once you’ve regained a healthy gut, lowered inflammation, and rebalanced the microbiome, you can absolutely reintroduce coffee and reap its potential benefits.
Possible Side Effects of Coffee
One of the main concerns with coffee is that everyone reacts differently to caffeine. For fast caffeine metabolizers, the caffeine content in coffee doesn’t affect them or only gives them a slight lift in energy. For others, the amount of caffeine in just one cup of coffee can cause jitteriness, increased heart rate, and a general sense of their nervous system being hyperalert.
If you’re wanting to introduce black coffee for its wellness benefits, it’s best to slowly increase your consumption over time to reduce any possible caffeine side effects. If you know you’re sensitive to caffeine, you could also start with a decaf or half-caf blend.
Coffee is also a known diuretic — it makes you urinate more frequently. You may have heard that coffee is dehydrating for this reason. But research shows that moderate consumption does not cause dehydration in healthy individuals. Unless you’re consuming over six cups a day, there’s no reason to be concerned about dehydration as a possible side effect to coffee drinking .
Who Should Avoid Coffee?
Besides those with gut health issues, some people should avoid coffee. Specifically:
- Pregnant women should avoid consuming more than 200 mg of caffeine daily (whether from coffee, chocolate, or tea) due to weak evidence that higher doses of caffeine can cause preterm birth, low birth weight, and miscarriage [3, 4].
- People with type 2 diabetes could alter their glucose response by consuming caffeine. One study showed that the caffeine equivalent to 4-5 cups of coffee had stronger glucose responses after eating and higher average day time glucose concentrations . But this study was quite small, and each individual response probably varies. If you are diabetic, note how your blood sugar responds when you consume caffeine and make any necessary adjustments to your intake.
- People who are genetically predisposed to caffeine sensitivity may experience anxiety, hyperactivity, or a jittery feeling when they consume coffee [25, 26].
Does Coffee Contain Gluten?
If you are celiac or sensitive to gluten, good news — you don’t have to worry about coffee. Researchers looked at many coffee samples and tested for cross-reactivity with gluten. Most of the samples were cleared, minus a few highly processed instant coffee products. As long as you stay away from highly processed versions, coffee should not present a problem for gluten intolerances [27, 28].
Choosing freshly ground coffee or whole beans to grind yourself also reduces the risk of any gluten contamination that may occur during the manufacturing process if that is a concern .
Mycotoxins in Coffee
Some people have raised questions about the presence of mycotoxins — toxins produced by mold such as aflatoxins — in coffee. Mycotoxins can be damaging to human health and have been linked to cancer, immune issues, and liver damage. But while there are trace amounts of some mycotoxins found in coffee, they don’t seem to be at a level that would be cause for concern.
A 2015 Spanish study found that 53% of all coffee samples tested contained traces of mycotoxins, but these levels were not high enough to cause mycotoxin illness for consumers .
Still, everyone is different, and if you have been exposed to mycotoxin illness in the past, you may be more sensitive to these trace amounts. If you want to play it safe, purchase whole beans from a trusted coffee retailer and store them in a cool and dry environment.
Coffee While Fasting
Luckily for those who practice intermittent fasting, coffee can be consumed whether you are in a fasting period or not. Typically, I recommend drinking freshly ground black coffee for any coffee drinker, but a splash of plant or dairy milk shouldn’t hurt if you need to make it more palatable.
Adding MCT or coconut oil to your coffee can also help you feel fuller for longer while fasting and has the added benefits of medium chain triglycerides. Animal and human studies show that these fatty acids support glucose metabolism and improve insulin resistance [30, 31, 32].
Again, consuming coffee with added fat may worsen symptoms for those with IBS-D, so pay attention to what your body tells you about what foods you can or can’t tolerate.
The argument about whether coffee is good for you or not is still debated, but the scientific evidence suggests that it actually has some health benefits for many people. If you enjoy coffee or you’re curious about its potential benefits, enjoy moderate consumption daily. Your coffee tolerance or sensitivity may change over time, so it’s always good to take breaks if you think you need to and reintroduce coffee later on.
Like anyone else, coffee drinkers can benefit from a healthy diet and lifestyle. For further guidance on the right therapeutic diet for you, reach out to us at the Ruscio Institute for Functional Medicine and schedule a consultation.