A new study on the consumption of coffee has revealed the world's most common recreational drug affects our metabolism far more deeply than we realised.
The results describe a number of knock-on effects that impact upon several important body systems, suggesting our daily coffee habit might have a complex range of benefits and risks to our health.
It seems hardly a month goes by when there's a new discovery that coffee is either good for our health and helps you live a longer life, or a potential danger and cancer risk.
In between the hype and the headlines, the truth is always more complicated. And this latest study shows us just why – it turns out the compounds in our daily cup of joe change more metabolites in our blood than previously known.
The investigation entailed 47 coffee drinkers to give up the habit for a month before throwing back four cups of coffee each day for the next 30 days. Following that, they upped their coffee intake to eight cups.
All the while, researchers were taking blood samples to analyse changes in biochemistry that result from consuming food and drink.
The resulting profile revealed 115 metabolites were impacted by the consumption of coffee. A total of 82 of those chemicals were already known, and could be mapped to 33 metabolic pathways, a number of which were completely new relationships.
The exact consequences of these changes weren't explored, but what is apparent is that we really should be paying attention.
"These are entirely new pathways by which coffee might affect health," says the study's lead author Marilyn Cornelis from Northwestern University Feinberg School of Medicine.
"Now we want to delve deeper and study how these changes affect the body."
For example, drinking around eight cups of coffee a day has a knock-on effect causing a drop in the kinds of neurotransmitters mimicked by cannabis.
In other words, where cannabis ramps up our body's endocannabinoid system, something in coffee seems to drive down the system's neurotransmitters, putting it into low gear.
Our body tends to decrease its production of endocannabinoids in times of stress, making the researchers question the relationship between coffee and how our body adapts to change.
"The increased coffee consumption over the two-month span of the trial may have created enough stress to trigger a decrease in metabolites in this system," says Cornelis.
"It could be our bodies' adaptation to try to get stress levels back to equilibrium."
That's not all the endocannabinoid system does, though. It has a hand in everything from cognition, to sleep, to appetite.
"The endocannabinoid pathways might impact eating behaviours," says Cornelis, referring to the classic link between cannabis and 'the munchies'.
Another metabolic pathway worth further investigation is the one responsible for keeping our steroids in check.
Steroids cover a variety of chemical messengers that zip around through our blood, controlling everything from growth to sexual characteristics.
In particular, the researchers found metabolites associated with the excretion of steroids went up with coffee consumption, hinting at a connection between the beverage and elimination of steroid compounds from our body.
Exactly what components of coffee are responsible for these kinds of changes is not yet clear.
The findings might go some way to explain why coffee seems to have so many health benefits, such as helping in weight management and reducing the risk of type 2 diabetes.
"This is often thought to be due to caffeine's ability to boost fat metabolism or the glucose-regulating effects of polyphenols (plant-derived chemicals)," says Cornelis.
"Our new findings linking coffee to endocannabinoids offer alternative explanations worthy of further study."
Given how popular coffee is all over the globe, it's strange to think there is so much we still don't know about its impact on our health.
Hopefully more studies like this one will help us fine tune its benefits and help us determine how to get the most out of our frequent cappuccinos.
This research was published in the Journal of Internal Medicine.