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The health effects of coffee are controversial.

Despite what you may have heard, there are plenty of good things to be said about coffee.

It’s high in antioxidants and linked to a reduced risk of many diseases.

However, it also contains caffeine, a stimulant that can cause problems in some people and disrupt sleep.

This article takes a detailed look at coffee and its health effects, looking at both the positives and negatives.

Coffee is rich in many of the nutrients naturally found in coffee beans.

A typical 8-ounce (240-ml) cup of coffee contains (1):

  • Vitamin B2 (riboflavin): 11% of the DV
  • Vitamin B5 (pantothenic acid): 6% of the DV
  • Vitamin B1 (thiamine): 2% of the DV
  • Vitamin B3 (niacin): 2% of the DV
  • Folate: 1% of the DV
  • Manganese: 3% of the DV
  • Potassium: 3% of the DV
  • Magnesium: 2% of the DV
  • Phosphorus: 1% of the DV

This may not seem like a lot, but try multiplying it with the number of cups you drink per day — it can add up to a significant portion of your daily nutrient intake.

But coffee really shines in its high content of antioxidants.

In fact, the typical Western diet provides more antioxidants from coffee than from fruits and vegetables combined (2, 3).

Summary Coffee contains a small amount of some vitamins and minerals, which add up if you drink many cups per day. It is also high in antioxidants.

Caffeine is the most commonly consumed psychoactive substance in the world (4).

Soft drinks, tea and chocolate all contain caffeine, but coffee is the biggest source.

The caffeine content of a single cup can range from 30–300 mg, but the average cup is somewhere around 90–100 mg.

Caffeine is a known stimulant. In your brain, it blocks the function of an inhibitory neurotransmitter (brain hormone) called adenosine.

By blocking adenosine, caffeine increases activity in your brain and releases other neurotransmitters like norepinephrine and dopamine. This reduces tiredness and makes you feel more alert (5, 6).

Numerous studies demonstrate that caffeine can lead to a short-term boost in brain function, improving mood, reaction time, vigilance and general cognitive function (7, 8).

Caffeine can also boost metabolism by 3–11% and exercise performance by 11–12%, on average (9, 10, 11, 12).

However, some of these effects are likely short-term. If you drink coffee every day, you will build up a tolerance — and with it, the effects will be less powerful (13).

Summary The main active compound in coffee is the stimulant caffeine. It can cause a short-term boost in energy levels, brain function, metabolic rate and exercise performance.

Alzheimer's disease is the world’s most common neurodegenerative disease and a leading cause of dementia.

Studies have shown that coffee drinkers have up to a 65% lower risk of developing Alzheimer's disease (14, 15, 16).

Parkinson's is the second most common neurodegenerative disease and is caused by the death of dopamine-generating neurons in the brain.

Coffee drinkers have a 32–60% lower risk of Parkinson's disease. The more coffee people drink, the lower the risk (17, 18, 19, 20).

Summary Several studies show that coffee drinkers have a much lower risk of dementia, Alzheimer's disease and Parkinson's disease in old age.

Type 2 diabetes is characterized by elevated blood sugar levels due to resistance to the effects of insulin.

This common disease has increased tenfold in a few decades and now affects over 300 million people.

Interestingly, studies show that coffee drinkers may have a 23–67% reduced risk of developing this condition (21, 22, 23, 24).

One review of 18 studies in 457,922 people associated each daily cup of coffee with a 7% reduced risk of type 2 diabetes (25).

Summary Numerous studies have shown that coffee drinkers have a significantly lower risk of type 2 diabetes.

Your liver is an incredibly important organ that has hundreds of different functions in your body.

It is sensitive to excess alcohol and fructose intake.

The end stage of liver damage is called cirrhosis and involves most of your liver turning into scar tissue.

Coffee drinkers have up to an 84% lower risk of developing cirrhosis, with the strongest effect for those who drink 4 or more cups per day (26, 27, 28).

Liver cancer is also common. It is the second leading cause of cancer death worldwide. Coffee drinkers have up to a 40% lower risk of liver cancer (29, 30).

Summary Coffee drinkers have a significantly lower risk of cirrhosis and liver cancer. The more coffee you drink, the lower your risk.

Depression is the world's most common mental disorder and leads to a significantly reduced quality of life.

In one Harvard study from 2011, people who drank the most coffee had a 20% lower risk of becoming depressed (31).

In one review of three studies, people who drank four or more cups of coffee per day were 53% less likely to commit suicide (32).

Summary Studies show that people who drink coffee have a lower risk of becoming depressed and are significantly less likely to commit suicide.

Given that coffee drinkers have a lower risk of many common, deadly diseases — as well as suicide — coffee could help you live longer.

Long-term research in 402,260 individuals aged 50–71 found that coffee drinkers had a much lower risk of dying over the 12–13 year study period (33):

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The sweet spot seems to be at 4–5 cups per day, with men and women having a 12% and 16% reduced risk of death respectively.

Summary Some studies demonstrate that — on average — coffee drinkers live longer than non-coffee drinkers. The strongest effect is seen at 4–5 cups per day.

It wouldn't be right to only talk about the good without mentioning the bad.

The truth is, there are some negative aspects to coffee as well, although this depends on the individual.

Consuming too much caffeine can lead to jitteriness, anxiety, heart palpitations and even exacerbated panic attacks (34).

If you are sensitive to caffeine and tend to become overstimulated, you may want to avoid coffee altogether.

Another unwanted side effect is that it can disrupt sleep (35).

If coffee reduces your sleep quality, try quitting coffee late in the day, such as after 2:00 p.m.

Caffeine can also have diuretic and blood pressure-raising effects, though these usually dissipate with regular use. However, a slight increase in blood pressure of 1–2 mm/Hg may persist (36, 37, 38).

Summary Caffeine can have various negative effects, such as anxiety and disrupted sleep — but this depends greatly on the individual.

Another issue with caffeine is that it can lead to addiction.

When people consume caffeine regularly, they become tolerant to it. It either stops working as it did, or a larger dose is needed to produce the same effects (39).

When people abstain from caffeine, they get withdrawal symptoms, such as headaches, exhaustion, brain fog and irritability. This can last for a few days (40, 41).

Tolerance and withdrawal are the hallmarks of physical addiction.

Summary Caffeine is an addictive substance. It can lead to tolerance and well-documented withdrawal symptoms like headaches, tiredness and irritability.

Some people opt for decaffeinated coffee instead of regular.

Decaffeinated coffee is usually made by rinsing coffee beans with chemical solvents.

Each time beans are rinsed, some percentage of the caffeine dissolves in the solvent. This process is repeated until most of the caffeine has been removed.

Keep in mind that even decaffeinated coffee does contain some caffeine, just much less than regular coffee.

Summary Decaffeinated coffee is made by extracting caffeine from coffee beans using solvents. Decaf does not have all of the same health benefits as regular coffee.

There are some things you can do to maximize the beneficial health effects of coffee.

The most important is to not add a lot of sugar to it.

Another technique is to brew coffee with a paper filter. Unfiltered coffee — such as from a Turkish or French press — contains cafestol, a substance that can increase cholesterol levels (42, 43).

Bear in mind that some coffee drinks at cafés and franchises contain hundreds of calories and a lot of sugar. These drinks are unhealthy if consumed regularly.

Finally, make sure to not drink excessive amounts of coffee.

Summary It is important not to put a lot of sugar in your coffee. Brewing with a paper filter can get rid of a cholesterol-raising compound called cafestol.

Some people — especially pregnant women — should definitely avoid or severely limit coffee consumption.

People with anxiety issues, high blood pressure or insomnia might also want to reduce their intake for a while to see if it helps.

There is also some evidence that people who metabolize caffeine slowly have an increased risk of heart attacks from drinking coffee (44).

Additionally, some people are concerned that drinking coffee may increase their risk of cancer over time.

While it’s true that roasted coffee beans contain acrylamides, a category of carcinogenic compounds, there is no evidence that the small amounts of acrylamides found in coffee cause harm.

In fact, most studies suggest coffee intake has no effects on cancer risk or may even reduce it (45, 46)

That said, coffee can have important beneficial effects on health for the average person.

If you don't already drink coffee, these benefits are not a compelling reason to start doing it. There are downsides as well.

But if you already drink coffee and you enjoy it, the benefits appear to far outweigh the negatives.

It's important to keep in mind that many of the studies referenced in this article are observational. They examined the association between coffee drinking and disease outcomes but do not prove a cause and effect.

However, given that the association is strong and consistent among studies, coffee may indeed play a positive role in your health.

Though it was demonized in the past, coffee is likely very healthy for most people, according to scientific evidence.

If anything, coffee belongs in the same category as healthy beverages like green tea.