Coffee is a hugely popular drink, but many people are concerned that it may cause cancer. Others claim that drinking coffee offers health benefits and may even prevent cancer. So, what does the evidence say?
Cancer is a complex disease, and it is not always easy to determine its cause. Researchers have investigated many different substances to find out if they increase a person's risk of cancer. Substances that can cause cancer are known as carcinogens.
The International Agency for Research on Cancer (IARC) reviewed more than 1,000 studies in humans and animals and did not find adequate evidence to indicate that coffee is a carcinogen.
However, more research into the link between coffee and cancer is necessary. A 2017 study suggests that drinking coffee may, in fact, lower the risk of developing specific forms of cancer.
Although older studies did sometimes find a link between drinking coffee and developing cancer, the cause was often smoking rather than coffee. People who smoke also tend to drink coffee.
Roasted coffee beans contain a substance called acrylamide, which is a byproduct of the roasting process.
The IARC classify acrylamide as a Group 2A probable carcinogen. This means that there is substantial evidence suggesting that acrylamide can cause cancer in animals. However, more research is necessary to determine if it also increases the risk of cancer in people.
Coffee does not contain acrylamide unless it has come from roasted coffee beans. People who are concerned about acrylamide can choose an alternative type of coffee.
Acrylamide also occurs in:
- cigarette smoke
- industrial processes, such as making plastic, paper, and dyes
- starchy foods that need cooking at a high temperature, for example, fries and potato chips
- food packaging and some adhesives, in small quantities
People can limit their exposure to acrylamide by being aware of cooking methods and not smoking. They can roast or bake potatoes instead of frying them and toast bread until it is light rather than dark brown.
There is also a link between drinking very hot liquids and cancer of the esophagus, or food pipe. Drinking coffee that is hotter than 149ºF may increase a person's risk of developing esophageal cancer. Therefore, it is best to allow coffee to cool slightly before drinking it, particularly if it does not contain milk.
Most cancers occur due to a combination of factors, including people's genes, environment, and lifestyle.
Some key risk factors for cancer include:
- being overweight
- an unhealthful diet
- drinking alcohol
- sun exposure
- workplace risks, such as exposure to certain chemicals and radiation
- specific inherited genes, although this is a relatively uncommon cause
These risk factors can combine to increase the likelihood of a person developing cancer. For example, someone may have an unhealthful diet and not do enough exercise.
Drinking coffee as part of a healthful lifestyle is unlikely to be a health risk, but excessive coffee consumption can cause health problems. Coffee contains caffeine, which is a stimulant that makes the brain more alert and temporarily increases blood pressure.
People who have heart problems may choose to avoid coffee if they experience heart palpitations after drinking it. Coffee can also cause acid reflux in some people and may irritate the stomach.
Drinking coffee in the evening can disrupt sleep, and a good night's sleep is essential for health. It might be beneficial to replace coffee with a decaffeinated version or a herbal tea later in the day.
Roasted coffee beans contain some acrylamide. Coffee drinkers can avoid this chemical by choosing unroasted coffee beans, although these do taste very different. A variety of unroasted coffees are available to purchase online.
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Doctors generally also suggest that women who are pregnant or breast-feeding limit their caffeine consumption. However, the guidelines on this vary and can be difficult to follow because coffee strength differs too. People trying to limit their coffee intake may wish to seek medical advice or cut out coffee and other caffeinated products completely.
If a person wants to reduce the amount of coffee that they drink, they should do so slowly. Cutting down on caffeine can cause headaches. Replacing coffee with tea, decaffeinated coffee, water, or herbal teas can reduce a person's caffeine intake. Black teas and some herbal teas, such as green tea, do contain caffeine but usually less than a cup of coffee.
The study compared people who drank no coffee with people who drank the following amounts of coffee each day:
- approximately 4–7 cups
- about 1–3 cups
- one extra cup
The researchers found that all the groups drinking coffee had a lower rate of cancer than those who did not drink any coffee. People who drank more coffee had a reduced risk of developing the following cancers:
The study did not find a strong link between coffee consumption and the following cancers:
Other benefits of drinking coffee included a lower risk of death from all causes and a lower risk of heart disease, liver disease, and Parkinson's disease. The researchers found that drinking 3–4 cups of coffee per day gave the most benefit.
Coffee also contains antioxidants. These are substances that may stop or slow down cell damage. There is a need for more research on the potential health benefits of antioxidants.
Current research suggests that coffee is unlikely to cause cancer. It may reduce the risk of developing certain types of cancer, but there is not yet enough scientific evidence to confirm this.
As part of a healthful diet, coffee is likely to be beneficial. Drinking up to 4 cups of coffee a day should not pose any risks to health and may reduce the risk of certain diseases.