is coffee bad for you

Is Coffee Bad For You: Can Drinking Coffee Be Bad For You?

Is Coffee Bad For You?

At Black Ink, we drink around five or six cups (8 fluid ounces) of coffee every day. we have often wondered, is this a good thing or a bad thing for our health? As humans, we tend to focus on the bad, so let's do that. So, is coffee bad for you?

For those that require the too long, didn't read version, and want to know if coffee is bad for you, let us do our best to simplify it. Coffee can be both good and bad for you depending on a few variables, like how much caffeine in a cup of coffee based on your brewing method.

Typically, most research has toted that coffee (caffeine) is good for you in moderation as it can improve health, mental alertness, mental performance and physical performance. For those with preexisting heart conditions, it would be wise to consult with a doctor for the best way to proceed.

Of course, as coffee geeks, we like to know just how much coffee (caffeine) we can consume and what is actually happening within the body. Especially for those of you that enjoy drinking caffeine in the form of espresso shots. Personally, I could drink ten lattes a day! So, let's look at the scientific evidence behind whether drinking coffee is good for you or bad for you.

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What Does Caffeine Do?

sleeping dog

For starters, what does caffeine do? Well, as you might know, coffee contains caffeine and caffeine is a natural stimulant which blocks one of the neurotransmitters in the brain called adenosine.

Adenosine is unique because it's an inhibitory neurotransmitter, its main action is to dampen down brain activity. Since caffeine remains in your system for a long time, it is safe to say that these neurotransmitters will remain blocked for quite a while. Even though most of our caffeine comes from coffee or tea, you should be aware that you may be consuming it elsewhere, like from dark chocolate.

When caffeine blocks adenosine, that actually increases overall neuronal firing in the brain and that increases the activity of other neurotransmitters, like dopamine, which ultimately stimulates changes in our energy, mood and attention.

Coffee has a few other components within it, other than just caffeine. However, because coffee is mostly caffeine, which causes the positive and negative effects, we will focus on that. Coffee's most famous effect is that it enhances our mental performance and it does that in three main ways.

Mental Alertness

girl coffee

Cognitive Functions 

Studies have shown that coffee improves cognitive function in terms of alertness and vigilance. There was a study conducted in 1987 where they gave 20 healthy male volunteers different doses of caffeine which showed that just 32 milligrams of caffeine, which is less than half a cup of coffee, or half a shot of espresso, was enough to increase their auditory vigilance.

In this study, they were more aware of the auditory stimuli around them and also there was an increase in their visual reaction. Lastly, they were able to respond to tasks quicker. Does this sound like you after you've had your morning cup of coffee?

Second, there was a scholarly paper from the European Food Safety Authority that reviewed 22 randomized, double blind, placebo controlled studies on the effect of caffeine and attention. They said that overall there was a cause and effect relationship between a 75 milligram serving of caffeine, which is approximately one regular cup of coffee, or a single shot of espresso, and increased attention and alertness.

Interestingly, they concluded that caffeine increases both selective attention and sustained attention. Selective attention is focusing on one thing at a time. Sustained attention is being able to focus for extended period of time (which is obviously very useful) and were studying or trying to be productive in any kind of way. We will discuss in more depth below related to how long caffeine lasts in your system, but it is important to note that you should be monitoring your caffeine consumption daily.

On top of that, there was a review from 2013 where they looked at 66 double blind placebo controlled trials which concluded that simple and complex attention tasks were consistently affected by caffeine consumption. Caffeine affected both reaction times and the accuracy on a variety of simple tasks, but also, it had the potential to enhance higher order processes involved in active monitoring and coordination of behavior such as task switching, response inhibition and interference.

Overall, they concluded that caffeine has clear beneficial effects on attention and that the effects are even more widespread than previously assumed. So we've got all this evidence that says caffeine, and therefore coffee as a whole, improves our alertness. We can certainly attest to that as it is how we get through most of my days and it is our go-to when we need to be focused and alert.

But, we already knew that, right? Anecdotally speaking, like whenever we have our cup of coffee, we feel like we are more alert and that you can actually focus more on the thing that you are doing. If you really want to get the most out of your cup of coffee, pair it with the keto lifestyle and you'll be as sharp as a tack!

Mental Performance

memory workout


There is a fair amount of evidence in scholarly literature that suggest that coffee improves our memory and recall. For example, there was a study from 2009 where they gave a high amount of college students six lists of 15 words each to memorize.

In some tests they gave the coffee drinkers the caffeine beforehand and in others they gave them a placebo. Overall, they found that the students who had caffeine were more able to recall the words in the list than the students who'd been given the placebo.

However, this study was quite interesting because the students who had caffeine were also able to recall the wrong words, like words that weren't on the list they'd been asked to memorize. These words were sort of related to the words there, just not quite.

So this wasn't a fully conclusive 100 percent study. But the authors did conclude that caffeine appears to intensify the strength of connections among list words, thereby enhancing both true and false memory. If memory is something that you struggle with, we still recommend doing more than just being a coffee drinker.


There is also some evidence that caffeine enhances the consolidation of memories. There was a study from Johns Hopkins University in 2014 that tested this exact hypothesis. While the majority of studies give people caffeine before they get asked to learn words, and then get tested on them, this study did the opposite.

This was a double blind, placebo controlled and randomized study that involved 160 students that they asked. After, they tested the performance of the groups. After 24 hours, the caffeine group and the placebo group were asked to learn the words. They concluded that caffeine enhanced performance 24 hours after administration, according to an inverted U-shaped dose response curve, this effect was specific to consolidation and not retrieval.

They also concluded that caffeine enhanced consolidation of Long-Term Memories in humans. However, it also says that they concluded that a dose of at least 200 milligrams is required to observe the enhancing effect of caffeine on consolidation of memory, which is about two regular cups of coffee. So, two cups of coffee a day, says John Hopkins University, is pretty legit, frankly, for improving the consolidation of memory.


Finally, the scientific evidence suggests that coffee can actually improve mood on top of all the other things that it does. Harvard University conducted a study in 2011, they used 50,000 female volunteers and it was a long attitudinal study over a 10 year period. Initially, at baseline, these women in the study didn't have any kind of severe symptoms of depression or clinical depression.

The study looked at what the correlation was between that coffee consumption and the subsequent risk of developing depression. They said that the risk of depression decreased in a dose dependent manner with increasing consumption of caffeine (coffee). This basically led them to conclude that the more coffee you drink, the less likely you are to be depressed. The actual causation aspect of that is probably a little bit dubious, but it's an interesting study nonetheless. This leads me to wonder how long caffeine would remain in their system for until they started to show signs of depression.

In 2016, we had a meta analysis of some studies that looked at 346,913 different people and they showed that 300 milligrams of caffeine, which is about three or four cups of coffee, could be helpful for those suffering with, or at risk of, depression. Personally, I've noticed that when I'm drinking caffeine, it really gives me a mental boost and it helps me get out of any slumps that I may be in. These 300 mg of caffeine are pretty close to the daily recommended amount of caffeine as the caffeine will remain in your system for over a day. However, when in doubt, you could always just look for some chocolate to boost your mood!

Physical Performance


physical performance

So those are some of the effects of coffee on a mental performance. We've talked about how it increases alertness, vigilance, memory, recall and even mood. Let's now talk about the effects of coffee on physical performance. The way this works is that, as we said, coffee contains caffeine and caffeine is an adenosine antagonist. It blocks the actions of the inhibitor, your transmitter, adenosine overall causing more neuronal firing in the brain.

When there's more neuronal firing in the brain, the brain feels the need to increase the amount of adrenaline in our body. As a result, our bodies produce more adrenaline, the adrenaline increases blood flow to our muscles, which then increases the heart rate. In a way, it makes us more pumped up, like we are essentially working out.


There is evidence that caffeine consumption can increase the amount of time you can exercise for until you become exhausted, which is known as stamina. There was a study from 1978 where they had nine competitive cyclists to basically cycle as much as they could until they were physically exhausted and couldn't cycle anymore.

In one of the tests, they gave a group coffee with caffeine beforehand. As for the other group, they gave them decaffeinated coffee. They found that in the caffeinated coffee group, they were able to exercise for 90.2 minutes before collapsing of exhaustion. However, the decaffeinated coffee group could only exercise for 75.5 minutes before they collapsed of exhaustion.

So, the fact that they drank coffee that contained caffeine, versus coffee that didn't contain caffeine, helped increase their performance time. This gain in performance (running) was about 20 percent, which are great results. Imagine two athletes that typically perform the same but then all of a sudden one of them does 20% better. Imagine Usain Bolt being 20% faster than he already is?


There's some research that suggests that coffee can reduce our perception of tiredness during exercise. For example, in 2015, the European Food Safety Authority published their official scientific opinion on the safety of caffeine, and that was a meta analysis of 23 randomized controlled trials looking at caffeine and sports performance. They concluded that a cause and effect relationship has been established between the consumption of caffeine and an increase in endurance capacity. Just remember, caffeine can remain in your system for a long time, so it is important to keep track of how much it you put into your body

Coffee Make Me Tired

It is not so much that coffee makes you tired, it is that you are starting to come down from the caffeine high, or sugar rush for those that like it sweet. As we mentioned, the caffeine is what helps blocks the adenosine receptors in our brains, which tricks us into being alert. When these start to wear off, not only will you start to feel more drained, it'll happen pretty quickly where you will feel tired and probably need a nap.

The next reason why you may be feeling tired, is from dehydration. Drinking a lot of coffee can dehydrate you which will make you feel drowsy. It is always recommended to drink twice as much water as you do coffee. And no, the water in the coffee doesn't count!

Last is sugar. For the people that load their coffee with sugar, you are most likely tired from the sugar rush followed by the crash. Mix these three together and it is no wonder why you are in a self induced coma at 3 PM in the afternoon after your second Starbucks pumpkin latte.


Next, we have some evidence that coffee can actually help a recovery from exercise as well. For example, there was a study from the University of Illinois which showed that caffeine consumption can reduce DOMS, or delayed onset muscle soreness, which is that pumping kind of pain that you get in your muscles a day or two after exercising. Although these are awful, the best thing to do is to go for a run or to repeat the exercise that caused them!

For the study, they had 18 men and split them up into two groups. One was a caffeine group and the other one was a placebo group. Naturally, they got these men to do loads of bicep curls at the gym. Next, they assessed how sore their muscles were a day, two days, three days, and five days after doing the bicep curls. They found that the group that had caffeine beforehand had significantly less sore muscles on day two and day three, which is when DOMS typically kicks in. Those that had caffeine had less sore muscles than those who didn't have caffeine.

Also, they did a final kind of test set where they did as many reps of bicep curls as they could until failure, most of us know this as a super-set, and the caffeinated group managed to get more reps than the placebo. Overall, they said that the decreased perception of soreness in the days after a strenuous resistance training workout may allow individuals to increase the number of training sessions in a given time period. This is just one of the many studies we found that suggests that caffeine might help our recovery time.

Banning Caffeine

Between 1984 and 2004, the World Anti-Doping Authority said that caffeine had such an effect on physical performance that they banned high quantities of caffeine from Olympic events. Then, in 2004, they said that caffeine actually didn't meet the criteria as an unfair performance enhancer. Now, everyone probably has coffee before an event because they know that caffeine improves your physical performance. If they aren't drinking coffee, they are most likely taking a caffeine-rich supplement. I would be interested to test how much caffeine these elite athletes are putting into their systems as they probably have so much caffeine, it stays in their systems for weeks!

Health Benefits

health benefits

So far, we've discussed that the studies generally show that coffee has a positive effect on our mental alertness, mental performance, and on our physical performance. There are some studies that show a link between coffee consumption, or caffeine consumption, and a reduction in long term health problems. Like most things, especially caffeine since it may remain in your system for quite some time, moderation is important. When safely consumed, the health benefits are quite impressive.

Micronutrients and Antioxidants

We know that coffee contains some key micronutrients like vitamins, B2, B3 and B5, which are naturally found in coffee beans. On top of that, coffee contains natural antioxidants as well. Antioxidants are useful chemicals that help fight the reactive oxygen species that form when our mitochondria respire and produce energy. There was a study from the Journal of Nutrition that showed that coffee was the single biggest source of antioxidant intake in the body when compared with a lot of other foods, including fruits, vegetables and cereals.

Neurodegenerative Conditions

Studies have showed that coffee consumption is negatively correlated with a bunch of long term health problems. For example, coffee is inversely correlated with the development of some neurodegenerative conditions. There was a systematic review and a meta analysis of 26 studies that were done in 2010. In these, they found that 300 milligrams of caffeine per day, which is three or four cups of coffee, reduced the risk of developing Parkinson's disease by 32 percent which is quite a large number. The authors from these studies came to the conclusion that there was an inverse association between caffeine intake and the risk of Parkinson's disease, which can hardly be explained by bias or uncontrolled confounding.

Alzheimer's Disease and Dementia

In relation to Alzheimer's disease, there was a study from 2010 that looked at 1409 individuals aged between 65 and 79. The study examined them over a 21 year period, which is a really long period of time and a whole lot of coffee! The participants showed that coffee consumption reduced the risk of developing Alzheimer's disease and dementia. The elderly were the lowest risk, which was a 65 percent decrease found in the groups that had between three and five cups of coffee per day.


There is also a negative correlation between coffee intake and type 2 diabetes. Looking at a meta analysis from 2018, with over 1 million people in total analyzed, the analysis showed a statistically significant inverse correlation between coffee consumption and the development of Type 2 diabetes. To quote from the study, they said that the risk of Type 2 diabetes decreased by 6 percent for each cup per day increase in coffee consumption, and those consuming five cups of coffee per day could reduce their risk by 29 percent.

Cardiovascular Disease

There is some evidence that moderate coffee consumption can help reduce cardiovascular disease. For example, there was a review in 2017 that says habitual consumption of three to five cups of coffee per day is associated with a 15 percent reduction in the risk of cardiovascular disease. Also, higher coffee consumption has not been linked to elevated cardiovascular disease risk. What this says is that the more coffee you drink, the lower your risk of cardiovascular diseases. They have not been able to show any links between drinking too much coffee and getting more cardiovascular disease.


Looking at a meta analysis from 2011, in which they looked at 11 prospective studies, that had over 10,000 cases of strokes occurring, there were over 450,000 participants. These studies showed the correlation that drinking two cups of coffee per day reduced your risk of stroke by 14 percent and drinking three cups of coffee per day reduced your risk of stroke by 17 percent. Although correlational does not equal causation, the data looks pretty good.


Finally, and probably most importantly, we found some evidence that coffee drinkers may be at a lower risk of certain types of cancer. The International Agency for Research on Cancer (IARC) published a review of over a thousand studies looking at the links between coffee and cancer. They found that there was no direct correlation between drinking coffee and you developing cancer. In fact, they found an inverse relationship between drinking coffee and developing certain types of cancer.

Originally there was some evidence that coffee was linked to reduced risks of liver cancer. However, the IARC said that a response analysis revealed a significant linear response relationship between coffee consumption and liver cancer risk. The subgroup analysis, stratified by variables like gender, geographic region and various factors indicated similar results within individual subgroups. Our meta analysis suggested that coffee consumption is inversely associated with liver cancer risk.

So, now that you know there is a negative correlation between the amount of coffee you drink and the likelihood of developing liver cancer, drink up!

Well, is it good for you?

coffee woman

Although coffee is good for you, we probably shouldn't get carried away and start drinking gallons of it because there are a few caveats that we have to keep in mind. I know most of you probably want a simple answer whether coffee is good or bad for you, but if you haven't learned by now, it's a little of both. Let me explain the negative side effects of drinking too much coffee.


Although we know that coffee can increase alertness and vigilance, we've got some evidence that says that too much coffee can cause anxiety, restlessness and agitation. For example, there was a review from 2010 that concluded that, at low doses, caffeine improves hedonic tones and reduces anxiety. While at high doses, there is an increase intense arousal, including anxiety, nervousness and a jitteriness. We all know, if you drink too much coffee, you get quite jittery, which could potentially be bad.

Sleep and Insomnia

Secondly, there is a lot of evidence that when we have caffeine, especially later in the day, that it can really negatively impact our sleep. So, for example, we've got this study from 2013 and they gave different people a 400 milligram dose of caffeine. So about four and a bit cups of coffee, either 0 3 or 6 hours before bedtime compared to a placebo group who had, well, a placebo pill. And they showed that this moderate dose of caffeine, whether you had it just before or three hours before or even six hours before bedtime, that had a significant negative impact on quality of sleep. And overall, we know that caffeine can remain in our system for up to nine hours. And so like people generally suggest and I start following this advice that you shouldn't drink any coffee after 2:00 p.m. because that like if you sleep at 9:00, 10:00 or 11:00 p.m., that could still have a negative impact on your quality of sleep.

How Long Does Caffeine Last

coffee cup

One thing we didn't mention very much on was how long does caffeine last in our systems, especially those that are wondering why coffee makes them tired. It turns out that caffeine has a half life of 4-6 hours, so that double espresso you gulped down at 8 AM will feel like a single espresso to your brain by noon. Although it takes caffeine roughly 45 minutes to be absorbed into your system, it can take a day or two for it to completely leave your system. Regardless of how long caffeine lasts in our system, the health benefits we receive from it are unprecedented.

Benefits of Coffee

So overall, is coffee good for you? Well, we've looked at some of the evidence, and the evidence does suggest that coffee does reliably improve alertness, vigilance, memory recall and even mood provide. Just don't have too much of it because having too much of it can then cause anxiety, jitteriness and restlessness. It is safe to say that the benefits of coffee outweigh the negative side effects.

There is some pretty good evidence that coffee is associated with an increased physical exercise output and also reduces muscle soreness and our perceived fatigue during exercise. More interestingly, we've got all of this correlational data that shows that coffee consumption tends to be linked to a decrease in things like dementia, Parkinson's, Alzheimer's disease, cardiovascular disease, strokes, diabetes and a few others.

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