You probably think taking a baby aspirin daily will reduce your risk of getting a blood clot. You’ve likely heard that a thousand times. It’s one of those pieces of medical common knowledge. But here’s the thing: it doesn’t work in about a third of people, and doctors don’t know why. It’s a phenomenon called aspirin resistance, and people who have it don’t get the anti-blood-clot benefits from the drug. But for people who do respond to aspirin, it works pretty well.
At the individual level, aspirin resistance is really important, obviously. But big randomized controlled trials suppress these important individual factors, leading to generic conclusions that don’t apply to a large swath of patients. Let’s simplify things a bit in attempt to discern how this works, then we’ll consider some other individual factors that don’t get captured by broad research conclusions.
What we’ve started to realize over the last few decades is just how unique each person really is. And we don’t have good systems in place for taking into account these individual factors in health research. Not long ago, scientists assumed that once we’d figured out the human genetic sequence, miraculous medical feats would become commonplace and amazing drugs that cured everybody would be rapidly developed. Well, we found the human genome sequence in 2001, and we still haven’t developed those miracle cures.
Part of the problem, scientists now realize, has to do with what we call epigenetics. Epigenetic processes regulate the real-world effects of our genes by modulating the rate at which genes are changed into proteins. Even identical twins, whose gene sequence is shared, often turn out quite different because of epigenetics. How we respond to a given medication has a lot to do with epigenetics too.
Many factors influence epigenetics — what you eat, your environment, what medications you take, etc. But there’s one factor that makes this issue more complicated: a person’s microbiome also influences his or her epigenetics. Your microbiome consists of all the non-human organisms in and on your body. You’re composed of at least as many non-human cells as you are human cells.
And here’s where it get’s bewilderingly complex: the cumulative genome of the microbiome, called the metagenome, is way, way bigger than the human genome, and it’s influenced by its own epigenetic processes.
What this all means is this: there are no two individuals on the planet whose genetics, epigenetics, microbiome, metagenome, and meta-epigenetics all match exactly. And all of these things influence how we respond to medications.