Coffee: Good or Bad?

Posted on March 3rd, 2015 by Seth Nickinson

Coffee is the most consumed beverage in the world. But is it good for you or bad for you? On balance, the latest research suggests that for most people, coffee is more beneficial than harmful.

Coffee Impacts: Summary

The most comprehensive and comprehensible review of reliable coffee studies we’ve found is this Harvard School of Public Health Research Summary. Here are some takeaways:

  • Drinking up to six cups a day of coffee is not associated with increased risk of death from any cause, or death from cancer or cardiovascular disease.
  • Some people may still want to consider avoiding coffee or switching to decaf, especially women who are pregnant, or people who have a hard time controlling their blood pressure or blood sugar.
  • It’s best to brew coffee with a paper filter, to remove a substance that causes increases in LDL cholesterol.
  • Coffee may have potential health benefits, but more research needs to be done.
pros and cons of coffee


What Counts As A Cup?

An important note from the scientific work. When they say “a cup,” they mean an 8 oz. cup of regular coffee with about 100 mg of caffeine. That’s not a 16 ounce grande brewed coffee at Starbucks, which has about 330 mg of caffeine.

The US Food and Drug Administration (FDA) finds the average amount of caffeine consumed in the US is approximately 300 mg per person per day – the equivalent to between two and four cups of coffee. This is considered to be a moderate caffeine intake, which according to many studies, can promote a variety of health benefits.

Maximum Dosage

The Mayo Clinic reports that generally, up to 400 milligrams (mg) of caffeine a day appears to be safe for most healthy adults. That’s roughly the amount of caffeine in four cups of brewed coffee, 10 cans of cola or two “energy shot” drinks.

Mortality Impacts: Probably Positive

As part of one of the largest population studies ever, 130,000 individuals were tracked on all kinds of health habits for several decades between their 40s and 70s.  Researchers “did not find any relationship between coffee consumption and increased risk of death from any cause. For the general population, the evidence suggests that coffee drinking doesn’t have any serious detrimental health effects.”

Rather, in the largest study of older adults – over 400,000 — done to date, the NIH found:

“Coffee drinkers were less likely to die from heart disease, respiratory disease, stroke, injuries and accidents, diabetes, and infections.”

These are simple associations, not causal connections, but still they are important. As NIH researchers said, “The mechanism by which coffee protects against risk of death — if indeed the finding reflects a causal relationship — is not clear, because coffee contains more than 1,000 compounds that might potentially affect health.”

Positive Coffee Impacts

Consumed plain, coffee is calorie-free beverage brimming with antioxidants, flavonoids, and other biologically active substances that may be good for health.

Most studies find an association between coffee consumption and decreased overall mortality and possibly cardiovascular mortality, although this may not be true in younger people who drink large amounts of coffee.

Research over the past few years suggests that coffee consumption may protect against type 2 diabetes, Parkinson’s disease, liver cancer, and liver cirrhosis. It also appears to improve cognitive function and decrease the risk of depression.

Coffee Benefits Infographic


The bulk of research suggests that coffee likely has health benefits, but more research needs to be done to definitively state the extent of those benefits.

Cancer and Coffee

In 2013, Medical News Today reported on a study suggesting that consuming three cups of coffee a day may reduce the risk of liver cancer by 50%, while another study suggests that drinking four cups a day could halve the risk of mouth and throat cancer.

Mental Health and Coffee

A study from the Harvard School of Public Health suggested that drinking between two and four cups of coffee a day may reduce suicide risk in adults by as much as 50%, while more recent research found that ingesting 200 mg of caffeine each day may boost long-term memory.

A caffeine habit in your 40s and 50s — three to five cups daily of the high-octane stuff, not decaf — seems to reduce by up to 70 percent the risk of Alzheimer’s and dementia in your 70s, a 2009 University of South Florida study found. A related study indicates that regular caffeine consumption can slow the rate of cognitive decline in older adults, especially those who already have a slight bit of cognitive impairment.

2 coffee cups

Source: Flickr user chichacha

Negative Impacts

Caffeine Is a Drug

Many of us forget that caffeine is a psychoactive substance – a drug that crosses the blood-brain barrier to stimulate the central nervous system

The effects of caffeine can vary in each individual, which may explain why there are mixed messages surrounding whether caffeine is good or bad for us.

If you’re drinking so much coffee that you get tremors, have sleeping problems, or feel stressed and uncomfortable, then obviously you’re drinking too much coffee.

Individuals with anxiety disorders are more susceptible to the “anxiogenic” effects of the compound.

Cigarette smokers metabolize caffeine twice as fast as non-smokers, meaning they can consume more with less effect. However, “caffeine metabolism is slower among infants, pregnant women and individuals with liver disease. In addition, some medications slow caffeine metabolism,” according to Dr. Steven Meredith of Johns Hopkins.

If you are a pregnant female, have difficulty controlling diabetes or high blood pressure, or if coffee gives you tremors or palpitations, you may wish to avoid it.

Ultimately, the effects of caffeine are different for different people.

caffeine parody poster

Source: Flickr user elizabethrs


High consumption of unfiltered coffee (boiled coffee, French press, Turkish) has been associated with mild elevations in cholesterol levels. Coffee contains a substance called cafestol that is a potent stimulator of LDL cholesterol levels. Cafestol is found in the oily fraction of coffee, and when you brew coffee with a paper filter, the cafestol gets left behind in the filter.  Espresso is somewhere in the middle; it has less cafestol than boiled or French press coffee, but more than paper filtered coffee.

Heart Disease and Metabolism

Some studies found that two or more cups of coffee a day can increase the risk of heart disease in people with a specific — and fairly common — genetic mutation that slows the breakdown of caffeine in the body. So, how quickly you metabolize coffee may affect your health risk.

The weight of evidence on whether coffee increases the risk of heart disease or certain cancers is clearly leaning toward suggesting the negative ramifications are associated with the other habits of coffee drinkers and not the coffee consumption itself.

Pregnant Women: Be Careful

For pregnant women, the jury is still out on whether high coffee or caffeine intakes increase the risk of miscarriage, but we know that the caffeine goes through the placenta and reaches the fetus, and that the fetus is very sensitive to caffeine; it metabolizes it very slowly. Therefore, even though the impacts are not definitive, it seems prudent for pregnant women to limit caffeinated beverages to one cup per day.

Sensitive Tummy

The AARP, looking out for our bellies, tells us:

  • Coffee’s not your friend if you’re prone to heartburn. Coffee is highly acidic and is irritating to the gastrointestinal tract. Switching to decaf won’t help: In fact some research has found that decaf increases stomach acid even more than caffeinated coffee. Neither will switching methods of brewing or roasting. Avoiding coffee is the only solution.
  • Caffeine’s not your friend if you have acid reflux. Caffeine seems to be the main culprit by relaxing the sphincter muscle that normally keeps stomach acid from bubbling up the esophagus. Decaf coffee has significantly less of a reflux effect, studies have found.

It Ain’t Just the Coffee

The “problem with coffee” is as much about the other things people tend to do while consuming it:

  • People who drink coffee are less likely to exercise and use dietary supplements, and they tend to have a less healthy diet.
  • Drinking coffee commonly happens while smoking cigarettes, which would negate pretty much anything positive you are doing at the same time.
  • Adding sugar, milk, creams, and syrup – which most coffee drinkers do – can boost the calorie count high enough that drinking coffee regularly leads to weight gain and a greater risk for Type 2 diabetes.


The data show that coffee has both overarching and specific positive health impacts, all of which need to be studied more closely as to how they work Some individuals need to watch out more than others for the negative impacts of coffee drinking, which are largely tied to metabolism of caffeine and all the stuff we add to or do while drinking coffee. So as we always say here at Project ACT, use moderation, and know your own body. But enjoy that morning cup of Joe.


Fun Coffee Facts

This part of the post is just for fun.

For instance:

  • There are about fifty different species of coffee. In different parts of the world, these coffee beans are grown naturally. Only the state of Hawaii produces coffee commercially in the US.
  • Coffee is the second most traded commodity around the world. Coffee stands second only to fuel oil.
  • According to legend and possibly history, coffee was first discovered by a herd of goats. An Ethiopian herder discovered a bean making his goats crazy in 9th century which was later termed as coffee beans.
  • New York inhabitants consume 7 times more coffee than people from any other US city.
coffee facts infographic