Many of us tend to view coffee as a fairly unhealthy habit, even if it is something that we need to get us through the day. However, research has been increasingly showing us that this assumption is mostly incorrect.
In fact, instead of being bad for us, coffee is associated with a number of health benefits. For that matter, coffee even manages to be the main dietary source of antioxidants for many people, although that’s partly because we drink so much of it.
The site Warrior Coffee offers some interesting insight into the advantages and disadvantages of coffee.
Now, many of the benefits of coffee do make a lot of sense, like the idea that it offers more energy and can help to improve mood (1). But, some of those benefits are less obvious, such as the connection between coffee and skin cancer.
That connection has been identified in a number of different studies, yet it hasn’t been entirely clear whether there truly is an association between coffee and skin cancer risk or why this would be the case.
One research study published in 2016 (Liu et al., 2016) examined the outcomes of the various studies into coffee intake and risk of malignant melanoma. They did this by conducting a meta-analysis, which aims to look at studies within a given area and determine the current level of information on the topic.
Some Underlying Principles
In this paper, the authors looked at a total of 7 different studies into the connection between coffee and skin cancer. Of these studies, 5 were considered cohort studies, while the remaining 2 were case control studies.
Collectively, the cohort studies involved a total of 844,246 participants, while the case-control studies used 1,689 participants.
A cohort study is a type of observational study, which looks a group of people (called a cohort). Typically, information is gathered from this cohort at the beginning of the study, which can include data like eating habits and levels of exercise.
The group is then followed for a period of time, with follow-up questions often administered. At the end of the study, measurements are typically taken, including information like weight and disease development.
Typically, such a study will be large in scope and may consider many different areas of health and wellbeing. Then, individual researchers will examine different sets of outcomes, such as the possible connection between coffee and skin cancer. Because of this, you may often find multiple studies that use data from the same cohort study.
The other type of study considered in this meta-analysis was a case control study.
A case control study tends to be less common but it is also a type of observational study. Here, subjects within two groups are compared to one another. In this situation, the process involved comparing people with malignant melanoma (the cases) to those who did not (the controls).
Both of these designs can be effective at determining patterns in the population, especially as cohort studies tend to involve a large number of people.
However, the designs are also limited when it comes to cause and effect. Specifically, both types are considered observational studies. This means that the authors compared patterns between groups or over time but they did not manipulate any variables.
Observational research is often essential when it comes to studying diseases, as it is unethical to put people in a treatment that could increase their risk of disease development.
In general, observational research tends to be great at seeing patterns but doesn’t have the ability to test cause and effect. As such, all of the studies that the meta-analysis looked at could only make educated guesses about the nature of the connection between coffee and skin cancer.
Outcomes of the Meta-Analysis
When considering the cohort studies collectively, the authors found this pattern:
The graph considers the risk of malignant melanoma, with 1 being the baseline risk level. With this graph, lower numbers indicate a lower risk of cancer. The relevant line to consider is the one that does not contain any breaks. The other two lines are indications that the observed relationship was statistically significant.
The authors found that there was a dose-specific response. This means that as coffee consumption increased, the relative risk of malignant melanoma decreased.
While this pattern was found for caffeinated coffee, a similar pattern was not present with decaffeinated coffee, suggesting that caffeine plays a role in the overall effect.
When the genders were considered separately, the authors found that coffee significantly decreased malignant melanoma risk in women but not in men.
Evidence Connecting Coffee to Skin Cancer
Overall, the meta-analysis supported the idea that caffeinated coffee can help to protect against malignant melanoma. The effect appears to be caused either by the caffeine or by the interaction between caffeine and coffee, as this was not observed in decaffeinated coffee.
The authors argued that this outcome may be because of bioactive compounds within coffee, including polyphenols and other classes of compounds.
This perspective is supported by other research, which suggests that coffee can help to protect against prostate (2), endometrial (3) and liver cancer (4). Likewise, coffee may help to product from some brain diseases (5,6,7).
At the same time, coffee is a complex drink that contains a large number of different compounds, many of which we don’t fully understand.
As such, it is very possible that some of these compounds could be having an effect on cancer development, in conjunction with the caffeine.
Nevertheless, despite these outcomes, it is important to note that the research thus far is fairly preliminary and relies entirely on observational studies. This means that there’s no way to be confident that the effect truly is what it appears to be.
Even so, other authors have discussed the implications of coffee for cancer. For example, the site Caffeine Informer talks about 10 different studies in this field.
More research still needs to be undertaken to learn more about the connection between coffee and skin cancer risk, including the precise mechanism behind this action.
But, in the meantime, this study is one more piece of evidence that says coffee truly is good for you, even if you are drinking multiple cups of it per day.
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