Coffee and Caffeine — How Much Should You Drink?

Coffee contains hundreds of bioactive compounds. In fact, it’s the single largest source of antioxidants for many people (1, 2).

Studies also show that coffee drinkers have a lower risk of conditions like type 2 diabetes, neurological disorders, and liver diseases (3).

However, you may wonder how much coffee is safe to drink, and whether excess intake has any risks.

This article explains how much coffee you can safely drink.

How much caffeine is in a cup of coffee?

Caffeine, an active ingredient in coffee, is the most commonly consumed psychoactive substance in the world (4).

Coffee’s caffeine content is highly variable, ranging from 50 to over 400 mg per cup.

A small home-brewed cup of coffee could provide 50 mg, while a 16-ounce (475-ml) Starbucks grande packs over 300 mg.

As a general rule, you can assume that an average 8-ounce (240-ml) cup of coffee offers around 100 mg of caffeine.

Several sources suggest that 400 mg of caffeine per day — the equivalent of 4 cups (945 ml) of coffee — is safe for most healthy adults (3, 5).

However, many people drink much more than that without any issues.

Keep in mind that many other sources of caffeine exist, including tea, soft drinks, energy drinks, chocolate, and certain medications (6, 7).

The caffeine content of your morning joe can range from 50 to over 400 mg. Many sources recommend 400 mg of caffeine per day as the safe upper limit for healthy adults.

Short-term symptoms of excess intake

If you drink too much coffee over a short period, you may experience mental and physical symptoms, including:

• restlessness
• anxiety
• dizziness
• upset stomach
• irritability
• insomnia
• fast heartbeat
• tremors

If you experience such symptoms after drinking coffee, you may be sensitive to caffeine and should consider cutting your intake or avoiding caffeine altogether.

While it’s possible to die from a caffeine overdose, this is next to impossible from coffee alone. You would have to drink more than 100 cups (23.7 liters) in a single day.

However, there are a few rare cases of people dying after taking caffeine supplements (8).

Ingesting too much caffeine can cause various symptoms, mostly related to your brain and digestive system.

People tolerate varying amounts

Caffeine affects people in different ways. Many genes have been discovered that affect people’s sensitivity to this stimulant (9, 10).

These genes affect the enzymes that break down caffeine in your liver, as well as receptors in your brain that are affected by caffeine.

The effects of caffeine on sleep are also genetically determined. Some people can drink coffee and go to sleep immediately, while others are kept awake throughout the night.

Depending on your genetic makeup, you may tolerate a lot of caffeine — or very little. Most people are somewhere in the middle.

Your acquired tolerance is also very important. Those who drink coffee every day can tolerate much more than those who drink it rarely.

It’s also important to realize that medical conditions can affect sensitivity to caffeine.

If you have anxiety, panic disorder, heart arrhythmia, high blood pressure, diabetes, or other medical conditions, you may tolerate less caffeine. If you want to know more about your tolerance, speak to your medical provider.

Sensitivity to caffeine is highly variable and depends on genes and receptors for caffeine in your brain.

Coffee and longevity

While high caffeine intake causes adverse side effects, coffee is associated with many health benefits. It has even been linked to increased longevity.

In one study in 402,260 people ages 50–71, those who drank 4–5 cups of coffee per day had the lowest risk of death over the 12–13-year study period (11).

Two other reviews backed similar results (12, 13).

However, research is mixed. One recent study found that drinking 4 cups or more per day was linked to an increased — not decreased — risk of death in people under age 55 (14).

Note that these and most other studies don’t specify whether “cup” refers to a standard 8-ounce (240-ml) cup or just a generic vessel that people may use to drink coffee, independent of volume.

Nonetheless, variations in volume between differently sized coffee cups are generally not very great.

Although the evidence isn’t settled, several studies suggest that coffee drinkers live longer — with the optimal amount of coffee being around 4–5 cups per day.

Coffee and disease risk

Coffee has also been linked to a reduced risk of various illnesses, including:

• Type 2 diabetes. The more coffee people drink, the lower their risk of type 2 diabetes. One study found a 7% decrease for each daily cup (15).
• Liver cirrhosis. Drinking 4 cups or more of coffee daily brings the greatest reduction — up to 84% — in liver cirrhosis, a severe consequence of some liver diseases (16, 17).
• Liver cancer. Your risk of liver cancer is reduced by 44% for every 2 cups daily (18).
• Alzheimer’s disease. In one study, 3–5 cups per day were linked to a 65% decreased risk of Alzheimer’s disease (19).
• Parkinson’s disease. Coffee is associated with a reduced risk of Parkinson’s, with the greatest reduction seen at 5 cups or more per day (20).
• Depression. Studies have shown that 4 cups or more of coffee per day are linked to a 20% lower risk of depression and a 53% lower risk of suicide (21, 22).

Thus, aiming for 4–5 cups of coffee per day seems optimal.

As all of these studies were observational in nature, they cannot prove that coffee caused the reduction in disease — only that coffee drinkers were less likely to get these illnesses.

Yet, these results are worth bearing in mind.

In most cases, decaf coffee should have the same beneficial effects. An exception is for Parkinson’s disease, which seems to be primarily affected by the caffeine.

Coffee consumption has been linked to a reduced risk of many diseases, with the greatest effects seen at around 4–5 cups per day.

Caffeine during pregnancy

In pregnant women, caffeine can cross the placenta and reach the fetus. However, the fetus has problems metabolizing caffeine.

Some studies link high caffeine intake during pregnancy with an increased risk of miscarriage, stillbirth, premature delivery, and lower birth weight (23, 24, 25, 26).

It is generally recommended that pregnant women limit their intake to 100–200 mg of caffeine per day — about 1–2 cups (240—475 ml) of coffee.

However, many experts recommend avoiding coffee completely during pregnancy. If you want to be absolutely safe, this is a smart choice.

Concerns have been raised about caffeine’s effect on the developing fetus, so it’s generally recommended to avoid or minimize coffee intake if you’re pregnant.

Recommended intake

Evidence indicates that 4–5 cups of coffee per day may be the optimal amount.

This amount is linked to the lowest risk of premature death, as well as a lower risk of numerous common diseases, some of which affect hundreds of millions of people.

Of course, this doesn’t mean that you have to drink coffee.

People who are caffeine-sensitive, have certain medical conditions, or simply don’t like this beverage, should definitely avoid it.

What’s more, if you like coffee but find that it tends to give you anxiety or sleep problems, you may want to reduce or eliminate your intake.

Furthermore, you can easily negate the benefits of coffee by adding sugar or other unhealthy, high-calorie ingredients to it.

Still, it’s possible to optimize your java to obtain the maximum benefits.

Evidence suggests that 4–5 cups of coffee per day is associated with the greatest health benefits. However, if you’re sensitive to caffeine, you should aim for lower amounts or avoid coffee altogether.

The bottom line

For people who enjoy coffee, there’s very little evidence of harm — and plenty of evidence of benefits.

While 4–5 cups per day may be optimal, many people can tolerate more than that without any problems.

If you like drinking a lot of coffee and don’t experience side effects, there’s no reason to stop drinking it.