Coffee and cancer

Abstract

<p>You cannot imagine powering through the day without your favorite beverage being on your desk all the time. Have you ever wondered what the consequences might be? </p>

<p>It seems that even before you have opened your eyes, there’s already a kettle on the stove or the coffee machine is purring. On the way to work, you have another cup to go from the nearby coffee chop. Long meetings demand even more caffeine, and before you know it, you are at on the fourth cup of coffee, and it is just past lunchtime. It probably crossed your mind whether or not it is safe to drink so much coffee, but you have not had much time or simply, you did not want to think too much about it; caffeine addiction has developed long time ago and the willingness to cut down on the number of cups is out of reach.</p>

<p>Norway has a long tradition when it comes to coffee consumption. During the early 18th century, coffee supressed alcohol beverages as a “social lubricant” among upper class of Norwegian society. By the end of the 19th century, yearly coffee consumption in Norway had reached almost 4 kg per capita. At that time, even children drank coffee, and health authorities rose their concerns about its health effects for the first time somewhere around the 1850s. In 2016, the International Agency for Research on Cancer published a Monograph in which they have stated that coffee drinking was not classifiable as to its carcinogenicity in humans. What this means is that there is no convincing evidence that coffee consumption is harmful when it comes to risk of cancer. In fact, what the Agency further said is that coffee consumption might have a protective effect on developing certain types of cancer such as liver or uterine cancer. However, most of the research conducted was exploring the risk of drinking the amount of coffee, which would in Norway be considered as moderate. Indeed, between 1997 and 2011, average consumption of coffee in Norway was 9.4 kg/year per capita, second highest in the world, trailing only behind Finland. So what if the true effect of coffee on the risk of cancer kicks in only after consuming a high amount of the beverage? </p>

<p>The researchers from the Arctic University of Norway think they have the answer. In a recently published study, they aimed to investigate the effect of drinking more than seven cups of coffee per day on the cancer risk. They have used the information on coffee consumption that were collected during 90s from around 100 000 Norwegian women that are part of the ongoing Norwegian Women and Cancer Study. After approximately 20 years, the researchers used the information from the Norwegian Cancer Registry, and the participants’ unique ID number (confidentiality is always top priority) to identify those who were diagnosed with cancer in the meantime. Using these data and some fairly complex statistical analyses, the study authors found that even consuming large amounts of coffee on daily basis does not affect your chances of cancer, specifically bowel, breast, and cancer of the ovaries. They did find a two times increased risk of lung cancer among those women who drank more than 7 cups of coffee compared to women who drank no more than one. However, before you empty your coffee mug in a sink and call your GP for the referral to a nearest radiologist, let us put your mind at ease by telling you that this result is most likely because of smoking. Indeed, it is known that active smokers are more likely to be heavy coffee consumers, which has something to do with how caffeine and nicotine are treated by our bodies - more specifically that these substances are processed by the liver in the same way. To make a long story short, active smokers will need more caffeine compared to non-smokers in order to feel the effect of it. So, how did the researchers deal with this? Quite simple! They repeated the analyses by using only the women who had never smoked. The result – no increased risk of lung cancer even if you drink large amount of coffee. Moreover, the researchers from UiT combined the data from Norway (Norwegian Women and Cancer Study) and Sweden (Northern Swedish Health and Disease Study) to explore how coffee drinking was related to the risk of some cancer types that are rarely diagnosed. What they found in the analyses that involved almost 200 000 men and women, was that drinking more than 4 cups of filtered coffee a day was reducing the risk of pancreatic cancer for 25% compared to drinking no more than one cup of this type of coffee a day. On the other hand, coffee drinking was not influencing the risk of bladder, esophageal, kindey, and stomach cancers in any way. Finally, the researchers “lumped” together the results from all previously published scientific papers that aimed to determine if coffee drinking was affecting the risk of endometrial cancer. This specific study design when the results from the previously published studies are combined in a single statistical analysis is called “meta-analysis”. This type of analysis is of great importance in epidemiology, as it is used to summarize all of the existing evidence on some topic. The meta-analysis conducted at UiT has shown that coffee drinking was greatly reducing the risk of endometrial cancer. However, this effect of coffee seems to be apparent only in women that have body mass index over 30 (women with obesity). </p>

<p>So next morning, put on your coffee kettle on a stove, or fire up the coffee machine. On the way to work, do not fear to have another cup to go and enjoy your coffee during boring meetings. Rest assured that the coffee you have (been drinking) drunk would not affect your health, at least when it comes to cancer. However, as there are many other diseases, which still need to be researched in regards to coffee drinking, keep in mind that moderation, is always an option.</p>