You can stop blaming being tired.
This Essay article is part of a Narcity Media series. The views expressed are the author’s own and do not necessarily reflect the views of Narcity Media.
"It’s in your genes." We throw this phrase around all the time. Maybe we’re talking about eating habits or athletic ability — or even whether or not coffee makes you poop. For some traits, like eye colour, the connection is straightforward and uncontroversial. Blue-eyed parents, blue-eyed kids. Well, usually anyway. For others, like cancer rates or political leaning, the connection is complicated, maybe even contentious, but it's there. Yes, this includes the politics you regretted bringing up at Thanksgiving dinner.
In fact, there is a genetic connection to almost all of our biology but it’s never simple. Understanding the complexity may help us appreciate what genetics can — and can’t — tell us.
Is coffee drinking in your genes?
Let’s look at one of my favourite examples — coffee drinking. Can your genetics tell us something about how much coffee you are likely to drink? Absolutely. As in, your genetics could suggest that you probably like to drink a lot of coffee. Can those genetics tell us how much coffee you do drink? Absolutely not. Probabilities, not precise predictions. Genetics, and biology in general, is like that and coffee drinking is a good model of how our biology works.
How does coffee interact with your body?
When we down a cup of the magic elixir we call coffee, the caffeine it contains wakes us up by displacing a natural messenger of sleepiness called adenosine. But some of us wake up more than others — and our genetics can explain this.
The wake-up is caused by caffeine binding to a receptor in our brains called A2A. That receptor protein is a product of the A2A gene. We all have the latter, but different people have different forms of the gene, called alleles. Different alleles code for slightly different proteins and some bind adenosine — and caffeine — more strongly than others. In general, the stronger the binding, the stronger the effect. It's these alleles and these differences that give us, in part, our personal caffeine and coffee, biology.
But, binding is only half of the coffee biology. Your body also breaks caffeine down. As in metabolizes it. Digests it. The breakdown, driven by a liver enzyme called CYP1A2, is part of a broad detoxifying network. This detox is why we aren’t accumulating toxic levels of caffeine as we sip double espresso after a pumpkin spice latte. So, yay CYP1A2!
Also, but unrelated, don’t drink pumpkin spice lattes.
How do genetics impact coffee preference?
CYP1A2 alleles are often used to predict if someone is a fast or slow caffeine metabolizer, by personal genomics websites, for example. Fast metabolizers tend to drink more coffee. Tend to, when you look at thousands of people.
My personal CYP1A2 genotype suggests I drink "slightly" more coffee than average. I’d say this was an underestimate. I own over 100 coffee makers. I drink a lot of coffee. Translating a broad population-level trend to "you will drink more coffee" is a tricky and untidy business at best.
One reason for this messiness is that genes, and proteins, interact. Looking at only CYP1A2 or even both CYP1A2 and A2AR, won’t give us the complete story. More proteins are involved, but we’re still working to figure out which of the other twenty thousand-ish genes in our genome impact our response to the dark beloved beverage.
The other reason is that genetics influence our biology but they don’t determine it. While genetics play a role in things like height, eye colour, or even coffee consumption, biology is convoluted and genetics generally explains only a small percentage of that complexity. Often only 10% or less.
What else influences coffee consumption?
Receptor binding and enzyme breakdown absolutely play roles in how much coffee you drink, but so does your lifestyle. Is this your first cup of the day? How much coffee do you typically drink? What is the rest of your diet like — do you also consume other caffeinated bevies? How much sleep did you get last night? These all play a role.
Then there is also just good old random chance. Biology, and genetics, absolutely do roll the dice. For example, whether you're a typical “righty”, or one of the less than 15% of us who isn’t, likely comes down to genetics – and a flip of the metaphorical coin. How that second espresso shot hits you in the morning, causes productive wake-up or distracting jitters, may just come down to a biological coin flip.
Welcome to the world — the real world — of biology. It’s complex.
In the coffee version of that field, and elsewhere, what's in your genes, or jeans for that matter, is only the starting point and never the whole story.
Is "it" in our genes? For many, many, things the answer is yes, but a complicated yes. Our complex biology means that genetics can tell us something about the probabilities of risks involved, but genes are not the only players in the game. For things more life-impacting than coffee drinking, disease susceptibility or treatment responses come to mind, common sense and practical decisions are as important aspects of quality care and prevention.
This article's cover image was used for illustrative purposes only.