Coffee and cancer
- Coffee contains a variety of bio-active compounds that may have an impact on cancer risk.
- Antioxidant compounds may help to neutralise harmful free radicals and thus help to protect cells against damage that can lead to cancer.
- Specific compounds in coffee include compounds that appear to modify the processes that help eliminate toxins from the body.
- These natural detoxification processes may be influenced in some way by compounds including cafestol and kahweol.
- Studies with populations who consume coffee regularly suggest that it may be associated with reduced risks of some cancers, notably liver cancer, bowel cancer and mouth cancer.
- No adverse effect on risks of breast or ovarian cancer in women have been uncovered by studies.
- Questions about the impact on lung cancer remain unresolved, with a large study suggesting consuming two or more cups of coffee or tea was linked to more cases of lung cancer, but another study showing no correlation between coffee and lung cancer.
- To sum up the balance of risks or benefits of coffee, it appears to a reasonable choice in moderation for most people affected by cancer, with potential benefits for people at risk or with liver, bowel and mouth cancers.
When you’ve had a cancer diagnosis, or know you are at increased risk of cancer, it’s sensible to look at your lifestyle and ask if changes can be made that can support your health. Our choices of food and beverages, and lifestyle such as tobacco use and physical activity, can influence cancer risk as well as possibly impact the course of cancer after diagnosis. There is some complex and sometimes contradictory evidence on coffee with regards to cancer. Coffee is sometimes portrayed as an ‘unhealthy’ drink, but the facts suggest a more complex picture. In this article we’ll look at coffee and health risks, particularly with regards to cancer.
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Humans have been consuming coffee for centuries, since at least the 1400’s, when it was discovered in North Africa. Coffee has been cultivated and consumed in the Middle East and Arabia since then. In Europe coffee began to replace alcohol as a daily drink, which made workers more alert! When the infamous British king George III levied heavy taxes on tea in the British colony in North America, apart from triggering the war of independence, coffee became the drink of choice for many Americans1. So coffee consumption has a long thread running through human history, although its form will have changed considerably over the centuries, with different means of cultivation, processing and brewing.
Coffee is produced from the seeds that are obtained by removing the pith from coffee ‘cherries’. The seed, usually referred to as a bean, has very little taste unless roasted. Green coffee beans do contain some interesting healthful compounds, including chorogenic acids. They are antioxidant compounds that may have some cancer-prevention properties, some are transformed or destroyed by the roasting process2. We’ll look at these beneficial coffee compounds in more detail below.
Roasting coffee beans releases and develops the unmistakeable flavour. There are concerns that this process also produces acrylamides, compounds produced by high temperatures that are potential carcinogens, that is they may contribute to causing cancer. More on this topic below, and for a wider discussion about this subject of cancer-causing compounds in food, see our article Carcinogens (Link). These concerns about coffee and cancer will be unpacked in some detail and put into perspective with actual consumption.
Firstly, the Good Stuff – Coffee and Cancer Prevention
Coffee beans contain some interesting compounds including plant compounds called polyphenols which may help reduce some cancer risks. As antioxidants they may help to neutralise damaging free radicals that can cause disruption of genetic messages. Free radicals arise as part of normal cell behaviour and also from external sources such as environmental pollution, smoke and damaged dietary fats. Neutralising free radicals may help prevent them from damaging cell components, especially genetic material. Some laboratory research suggests that coffee polyphenols may act in this protective manner, and thus contribute to lower cancer risk. A myriad of compounds in the coffee bean have been identified and lab studies suggest that some can act on abnormal cells in the mouth and colon to reduce cancer risk3,4.
There appear to be other potential beneficial compounds in coffee that might act in other ways to reduce cancer risk5. Cafestol and kahweol are compounds present in the oil component of coffee that appear to affect the way that carcinogens are eliminated from the body. Our bodies have elaborate mechanisms that breakdown and eliminate compounds by processes called detoxification. They have evolved to protect us against toxins and they require nutrients to work effectively. Lab studies have examined how some compounds in coffee such as cafestol and kahweol may affect the pathways responsible for elimination of cancer-causing compounds. In the lab these two compounds were also found to have beneficial effects on prostate cells6.
As well as processing toxins, the detoxification processes in the liver also metabolise hormones such as estrogen, which promotes the growth of some cancers. Researchers have looked at whether coffee may affect the way that estrogen is broken down and eliminated. Lab studies do suggest that coffee may contain compounds that influence these mechanisms affecting hormone levels7, 8.
Laboratory studies are interesting, but actual studies of people provide more helpful real-life guidance. When populations who consume coffee are studied, firstly the results show differences for different cancer types but also some differences between ethnicities and with gender differences. Significant cancer risk reduction has been seen for bowel and liver cancer4, 5. For several other tumour types researchers have found no relationship between coffee and cancer risks, or a slight protective effect. For example two groups of researchers have each reviewed large number of studies of women and their risk of breast or ovarian cancer. They found that coffee and caffeinated beverage consumption did not increase risks of developing these cancers7, 8.
"To sum up the picture of risks or benefits of coffee, it appears to a reasonable choice in moderation for most people affected by cancer, with potential benefits for some cancers"
Potential negative aspects of coffee consumption and cancer risk
There are also some factors linked to coffee consumption that complicate the picture. For example habitually drinking very hot beverages may be linked to increased risk of esophageal cancer, and that can include coffee, but the damage is apparently linked to the heat damage that very hot beverages can cause. Also, people who drink coffee may or may not smoke tobacco, and so studies need to sort out the effects of these sol-called confounding factors. That allows the researchers to separate out a potential negative effect of smoking that can complicate the picture. Another group of cancer researchers reviewed evidence on urinary tract cancer9 and found that coffee had no impact on risk of developing these cancer in smokers. However, an international collaboration looked at long-term research covering 1.2 million American and Asian adults, following them for up to 8 years, and they did report that people having two or more cups of tea or coffee raised their risk of lung cancer, compared with people who drank neither. They suggested it was not linked to caffeine. Their conclusion was at odds with another study that showed no link between coffee and lung cancer risk10, 11. This question remains unresolved, and as with so many areas of nutrition where humans are in fact individual with different genetic constitutions and have complex diets and habits that interact.
Roasting coffee beans produces acrylamides, which are produced by high temperature treatments of many food products, especially commercially baked breads, potato chips and crackers. Acrylamides can be linked to increased cancer risk, they are considered probable carcinogens. Coffee acrylamide levels have been raised as a concern, such that some authorities have considered labelling coffee with warnings about acrylamide levels12. The amount of acrylamide per cup of coffee is very small, and in comparison with other sources of acrylamide is generally considered to be a low contribution to overall intake13.
Toxins from mould (mycotoxins) are a concern for many crops including coffee beans. Ochratoxin is produced by Aspergillus mould and controls on coffee bean harvesting storage and processing are important to minimise it14.
The way that coffee is brewed does have an impact on the composition of coffee, for example some compounds are filtered out by some processes15. Cafestol and kahweol are retained by espresso type coffee makers, and their consumption has been linked to high blood cholesterol with higher coffee consumption16. Therefore depending on your individual health concerns beyond cancer, this may influence choice of brewing method and daily coffee intake.
To sum up the picture of risks or benefits of coffee, it appears to a reasonable choice in moderation for most people affected by cancer, with potential benefits for those concerned about liver, bowel and mouth cancers.