Sometimes referred to as "survival juice" or a "liquid hug for your brain" by its fans, coffee is the second most consumed beverage in the world after good old H2O.
A myriad of scientific research studies have endeavored to explore the impacts of coffee on health: is it good for you? If so, in what quantities? How much coffee is too much coffee? Is coffee linked to certain health outcomes? And so on and so forth.
Typically, these studies take an observational format where investigators monitor study subjects without intervening or assigning a "treatment" so to speak. In coffee research, this essentially means coffee drinkers are compared to non-coffee drinkers for a variety of parameters.
Observational studies carry methodological limitations and can produce misleading results. In a study published in Clinical Nutrition, expert epidemiologist Elina Hyppönen and team at the Australian Centre for Precision Health turned to genetics to dig deeper into the impact of coffee consumption on health outcomes.
"Globally, we drink around three billion cups of coffee each day, so it makes sense to explore the pros and cons of this on our health," Hyppönen said.
What's a MR-PheWAS?
The scientists conducted a Mendelian randomization phenome-wide association study, or MR-PheWAS for short. This method is complementary to the wider known genome-wide association study approach, or GWAS. In a MR-PheWAS, the association between single nucleotide polymorphisms (genetic variants) and a large number of phenotypes is statistically estimated.
Here, the scientists used information from up to 333,214 participants of the UK Biobank to explore the causal association between genetically instrumented habitual coffee consumption, created a genetic risk score and screened for associations with disease outcomes.
"In this study, we used a genetic approach - called MR-PheWAS analysis - to establish the true effects of coffee consumption against 1117 clinical conditions," said Hyppönen.
A cautionary message
The overall results of the study demonstrate that moderate coffee consumption is mostly safe.
However, support for a possible causal relationship between habitual coffee consumption was obtained for four distinct diseases, including osteoarthrosis, arthropathy and obesity.
"Excess coffee consumption can lead to increased risks of certain diseases," Professor Hyppönen said. "For people with a family history of osteoarthritis or arthritis, or for those who are worried about developing these conditions, these results should act as a cautionary message."
She continued: "While these results are in many ways reassuring in terms of general coffee consumption, the message we should always remember is consume coffee in moderation - that's the best bet to enjoy your coffee and good health too."
Nicolopoulos, Mulugeta, Zhou and Hyppönen. (2020). Association between habitual coffee consumption and multiple disease outcomes: A Mendelian randomisation phenome-wide association study in the UK Biobank. Clinical Nutrition. DOI: https://doi.org/10.1016/j.clnu.2020.03.009.