I was raised in a household that didn’t drink coffee for religious reasons, and so I had never had a sip of it until my twenties. I came to the realization that I had been zealously following the religion based on faith and unsound reasoning. Unburdening myself of dogma left me with several exciting questions to answer – among them, “is coffee actually good or bad for me?”
The data presented below are based on our review of every scientific study on the health effects of coffee that we could get our hands on – scroll to the end for citations. We also ran our own survey to see what Americans thought about the health of coffee, and the results may surprise you:
The Health Effects of Coffee
You can make your coffee drinking even healthier in three ways:
Always use a paper filter.
Paper filters remove harmful chemicals like cafesterol and kahweol, which increase cholesterol.
Drink coffee cooler than 158 degrees Fahrenheit (70 Celsius).
Drinking very hot liquids increases the risk of throat cancer.
Eat some food, but eat mineral-rich foods without coffee.
Coffee blocks the absorption of minerals like iron , calcium, zinc, and magnesium. Drinking coffee with some food may help with pancreatic and other cancers.
We were surprised at how good coffee seemed to be for health, and began to wonder if people in America thought coffee was good or bad for health. We asked about 1,200 Americans a simple question: if I were to drink three cups of coffee per day (the national average) would it be beneficial to my health, detrimental to my health, or have no impact on my health?
Interesting. Despite the generally positive effects that coffee has on health and overall mortality, more people think coffee is detrimental to their health than beneficial, and most people think it just doesn’t do anything. There were some interesting findings: people in the northeastern United States, for example, were far more likely to think coffee is bad for them. We then compared the age of the survey participants, and found that the younger you are, the more likely you are to believe that coffee is bad for you.
We can’t really say why, but older people on average seem to think drinking three cups of coffee is a good idea. Perhaps older people are more aware of the cognitive benefits of coffee. Maybe it’s a generational culture difference, or maybe people born in the 50s are just wise. For those wanting more than a summary, here are the health effects of coffee, complete with sources and details.
Health Benefits of Coffee
Coffee drinkers may live longer overall according to a May 2012 study, with each cup slightly reducing the risk of death among older patients.
In perhaps the largest and most revealing of coffee-related studies, over 400,000 men and women were followed for 13 years. In that time, those who drank the most coffee (more than six cups per day) were the least likely to die, those who drank less were more likely to die, and those who drank none were most likely to die. Quoting from the study, “Inverse associations were observed for deaths due to heart disease, respiratory disease, stroke, injuries and accidents, diabetes, and infections, but not for deaths due to cancer.” (Emphasis added) The authors of the study are clear: correlation does not equal causation, and they don’t really know yet why coffee drinkers are living longer.
Both a 1999 and 2008 study also found that coffee drinkers were less likely to die of heart conditions. Interestingly, the same correlation was not found with tea.
General Cognitive Performance
Many people drink coffee because it helps them feel more alert and more focused. Studies have shown, however, that this is more than a mere feeling, and that the cognitive benefits of drinking caffeinated coffee are real. The cognitive benefits of drinking coffee appear to be immediate as well as cumulative.
One study had test subjects avoid caffeine for a set time, and then take either a sugar pill or a caffeine pill. Those who received the real caffeine pill showed an increased brain function in fMRI scans.
Two separate, independent studies measured current coffee consumption and lifetime coffee consumption, and then gave patients cognitive tests. Both lifetime and current coffee consumption were positively correlated with higher test scores, after adjusting for variables. Interestingly enough, lifetime consumption of caffeine in coffee was more strongly correlated with better test scores than current coffee consumption. The results are more pronounced in older people, especially in women. This may be at least partially due to the reduction in early-stage Alzheimer’s and dementia.
No cognitive benefit has been found for decaffeinated coffee.
Lowered Risk of Alzheimer’s and Dementia
Several studies have now shown conclusively that those who drink coffee have a greatly reduced chance of developing both Alzheimer’s and dementia. Those who drank two cups or more of coffee per day were far less likely to develop Alzheimer’s disease.  In another (longitudinal) study, coffee drinkers who drank 3-5 cups per day had a 65% lower chance of developing dementia.That’s good news for coffee lovers.
Lowered Risk of Cancers
Coffee drinking has been correlated with a lowered risk of oral (mouth), esophageal (throat),pharynheal  (head/neck), colon, skin, and liver cancers. There is also some correlation to a lowered risk of breast cancer, but only in postmenopausal women.Among the more surprising studies showed that coffee drinkers (3-5 cups / 24 – 40 oz.) have a 50% lower risk of liver cancer.
Some cancers have yet to be studies in relation to coffee consumption. Overall, it seems that cancer is correlated with lower rates of cancer, though this does not appear to translate into a lower risk of dying from cancer (see studies on longevity).
Reduced Risk of Parkinson’s
Several studies have shown that coffee reduces the risk of Parkinson’s disease significantly. Researchers adjusted for education level, alcohol consumption, and smoking rates (all of which are typically higher in coffee drinkers) and found that coffee drinkers were much less likely to develop the disease. For coffee drinkers who did develop the disease, the onset was delayed by an average of 8 years. (64 vs. 72). A longitudinal study confirmed the finding that coffee reduces the risk and onset of Parkinson’s.(10.4 per 10,000 vs. 1.0 per 10,000 person-years)
Protection of the Liver
In addition to apparently protecting against cancer of the liver, drinking four or more cups (as in 8 fl. oz. – there are usually two cups in a “cup”) of coffee reduced risk of cirrhosis of the liver by about 350% for alcoholic cirrhosis, and 70% in those who had non-alcohol-related cirrhosis. Positive results were also reported for hepatocellular carcinoma.All of these studies adjusted for other demographic and lifestyle variables. Obviously the best way to avoid alcohol-related cirrhosis is still to avoid more than a drink or two per day.
Lowered Risk of Gallstones and Gallbladder Disease
This effect was found in both men and women in two Harvard studies. Thousands of men and women were studied over 20 years, and both had similar findings: those who drank less coffee were more likely to have had a “cholecystectomy” – a removal of gallstones. It is thought that coffee stimulates the gallbladder, pushing out the material that would otherwise form a gallstone.
Recent analysis of studies shows that coffee can reduce the risk of type 2 diabetes by up to 50% for coffee drinkers. The authors of one study suggest that for every 8 ounces of coffee consumed, the risk of developing type 2 diabetes dropped by 7%.
Contrary to common belief that caffeine “stresses” your heart, coffee appears to actually reduce your risk of dying from cardiovascular disease. One study with excellent methodology and huge sample sizes found that those who drank those who drank the most coffee had a 38% lower risk of cardiovascular disease for men and 22% lower for women when compared to those who drank the least coffee. Another large study attempted to adjust for caffeine intake, and found a small (but statistically significant) benefit for even decaffeinated coffee.
The consumption of coffee is inversely correlated with occurrence of gout. The same benefits are not seen at all from caffeine consumption, but only with coffee. The risk of gout in a study of 46,000 men declined as coffee consumption increased, with heavy coffee drinkers (6+ cups) having a 60% reduced risk of gout.
Hydration (Contrary to Myth)
Contrary to popular belief, coffee does not dehydrate the body or cause an electrolyte imbalance if consumed in moderation. In fact, coffee is hydrating – as hydrating as water is.    Coffee is also not a very strong diuretic, as is commonly thought. Both findings have been confirmed by at least five solid studies.
Coffee does not produce a reduced exercise heat-tolerance either. In other words, caffeine and coffee should be fine (in moderation, which varies based on tolerance) for athletes, and need not be avoided for hydration purposes. 
A decrease in the symptoms of bronchial asthma was one of the very first reported health benefits of coffee, and modern studies have verified the fact. The scientists stated that “long-term moderate coffee consumption may not only reduce symptoms, but also prevent the clinical manifestation of bronchial asthma.”
Other Potential Benefits
Dental carries and plaque may be reduced by coffee consumption.
Roasted coffee appears to have strong antioxidant properties not fully recognized in raw coffee beans. Roasted coffee protected cells from oxidative stress, improving cell survival in hydrogen peroxide by about 350%. More research is needed to determine if that translates into fewer health benefits when drinking unroasted coffee.
In addition to the cancers listed above, some studies have suggested that coffee may protect against aggressive prostate cancer and reduce the occurrence of kidney stones. Additional research is needed on these subjects.
Is coffee good for you, then? In many ways, it appears as though the answer is “yes.” We should, however, examine coffee health benefits as well as risks before making a final decision.
Coffee Health Risks
Coffee is slightly acidic, and may damage the gastrointestinal track, especially where conditions already exists. Those with previous or present gastritis, colitis, and ulcers would do well to avoid coffee and other acidic or spicy foods. Coffee has not been shown to increase the risk of ulcers, but it has been shown to increase heartburn in some individuals.
Pregnant women may be at an increased risk for miscarriages if they consume more than 200mg of caffeine per day. For reference, the average caffeine content in an 8 oz. cup of coffee ranges from about 100-140mg. Study reviewers noted that while the debate rages on, it’s probably best to err on the side of caution and limit or eliminate the consumption of caffeine.
Coffee Stains Your Teeth
Enough said.You probably already knew that.
Cholesterol (Paper Filters May Reduce Risk)
As mentioned at the beginning of this article, coffee contains chemicals that may raise LDL levels slightly.  These chemicals are removed with paper filters, but not otherwise. Those with high cholesterol risks should either not drink coffee or use paper filters. 
Coronary Artery Disease (Paper Filters May Reduce Risk)
There is conflicting information as to whether coffee contributes to the disease. One study showed that drinking more than four cups of coffee (32 oz.) caused artery inflammation. Another study found that coffee may reduce inflammation in arteries, thus lowering the risk of heart diseases.
The difference, again, may be in the use of paper filters. This hypothesis is further bolstered by a study that found no correlation in coffee consumption and coronary heart disease, and others that showed an overall decreased risk for relevant coronary diseases.  Another factor may be that some people are not able to metabolize caffeine at regular rates – namely those taking birth control and those with rare genetic anomalies.
Stupidity and Alcohol
Coffee does not reverse the effects of alcohol. Coffee might make you feel more alert and safe to drive, but it’s just a feeling – not reality. Coffee does not “sober you up.” Do not attempt to compensate for intoxication with coffee consumption. 
Mixing caffeine and alcohol may be bad for your heart, too, since one is a depressant and the other a stimulant. No significant research has been completed on the topic due to the potential risk factors involved with human patients.
Caffeine Jitters and Sleeplessness
Coffee is a stimulant, and may therefore cause difficulty sleeping or an irregular sleep cycle. Some coffee drinkers feel jittery after drinking coffee. This should not be confused with clinical anxiety. Anxiety and anxiety disorders are different from “caffeineism,” or the “coffee jitters.” While those with anxiety may have feelings of anxiety amplified by caffeine, several studies failed to find any correlation between clinical anxiety and caffeine consumption. 
Other Potential Risks
There are conflicting facts in regards to coffee and cancer of the pancreas. One study found that coffee drinkers were less likely to develop the cancer, while another found that those who had been diagnosed with cancer were more likely to be coffee drinkers (after adjusting for the variable of smoking and not drinking coffee). It has been suggested that drinking coffee and smoking may have a more negative effect on health than either activity in isolation, but more research was recommended.
While it was previously believed that coffee might cause bladder cancer in men, some studies show no impact. Researchers in a meta-analysis of studies found that researchers claiming coffee caused bladder cancer said “that the best available data do not suggest a clinically important association between the regular use of coffee and development of cancer of the LUT in men or women.” The same appears to be true of high blood pressure.
The vast majority of the studies above studied correlation. Many of the scientists who shared their findings were quick to point out that their data cannot prove that coffee is the cause of the health effect. Noting these limitations is the sign of honest science, and so we wish to do the same.
First, our survey needs more than 1,200 participants, plain and simple. The sample size needs to be a few times larger to make conclusive claims. We do think it’s a good starting point, though, that will stimulate conversation. How much are we wasting if health researchers are the only ones learning what is healthy?
While many of the studies appear to show health benefits or risks, it could very well be that a third factor is causing both. Consider this potential example: coffee shops are generally very relaxing and somewhat social. When at home, many coffee drinkers take time to read the paper and relax on the patio as they drink their coffee. The health benefits noted above could be the result of reduced stress from the experience of drinking coffee, and have nothing to do with the coffee itself. While this made-up explanation is unlikely, we can’t rule out such variables until we understand the mechanisms and study cause in more depth.
Is coffee good or bad for you? In the author’s view it appears that the health benefits of coffee far outweigh the health risks – especially with proper use and preparation. That said, coffee isn’t for everyone, and pregnant women and people with iron deficiencies, gastrointestinal problems, hypertension, etc. should probably avoid drinking large quantities of coffee. Otherwise, coffee seems to be quite healthy and quite beneficial all-around.
Though drinking coffee appears to have several benefits, these effects pale in comparison to an active lifestyle, low body fat, and eating fruits and vegetables.
Disclaimer: While the research above was thoroughly examined, it is possible that I have misunderstood the research. It’s also worth noting that I love coffee, and may have unintentionally biased my findings despite my effort at fairness. I am not a medical doctor – the information above is presented for your information only. Please consult with a medical professional before making any changes to your lifestyle.
Please let me know if you think we have misinterpreted any of the science cited in this article, or if you have located additional studies we should consider.