The Real Question Isn't “Is Coffee Good For You?”

That question has been argued for forty years and it will never resolve, because it's the wrong question. Coffee headlines contradict each other for a simple reason: the studies keep averaging together two populations that respond to caffeine in opposite directions.

An enzyme called CYP1A2 handles roughly 95% of the caffeine you consume. A common variant in the gene that codes for it (rs762551) determines how fast that enzyme works — and it's essentially a coin flip. Carry the A/A version and you're a fast metabolizer. Carry a C and you're a slow metabolizer, which is about half of people.

This is not a small effect. In a landmark case-control study of over 4,000 adults published in JAMA, slow metabolizers who drank two to three cups a day had a meaningfully higher risk of nonfatal myocardial infarction — and the risk climbed further at four or more cups. In fast metabolizers, the same intake carried no increased risk at all. Moderate intake actually tracked with lower risk.

Same cup. Same dose. Opposite answer. Which is exactly why general advice about caffeine is close to useless — and why knowing your genotype turns it into an actual decision.

Two Genotypes, Two Different Drugs

Genotype A/A

Fast Metabolizer

Clears caffeine quickly. Coffee at moderate intake is generally neutral to favorable, and the ergogenic benefit before training is real and reproducible.

Practical read: caffeine is a tool you can use deliberately.

Genotype A/C or C/C

Slow Metabolizer

Caffeine lingers. Higher intake has been linked to increased risk of nonfatal MI and to developing hypertension — associations that do not appear in fast metabolizers.

Practical read: dose and timing stop being optional.

There's a Second Gene

CYP1A2 controls clearance. ADORA2A controls sensitivity — how strongly your adenosine receptors react. It's why some people get anxious and sleepless on one small cup while clearing it normally. Two separate questions, two separate answers.

Genes Aren't the Whole Story

Smoking speeds CYP1A2 up. Pregnancy and oral contraceptives slow it down substantially. Your genotype sets the baseline — your physiology and medications move it. That's why the genotype gets read alongside your blood pressure, sleep data, and labs, never in isolation.

~50%Are Slow Metabolizers
2–10 hrsHalf-Life Range
One TestAnswers It For Life

Three Things Worth Doing This Week

  1. Set a caffeine curfew

    No caffeine within 8–10 hours of bed. In a controlled trial, 400 mg taken six hours before bedtime still measurably degraded sleep — and the participants didn't notice.

  2. Actually count your milligrams

    Coffee, pre-workout, energy drinks, and green tea add up fast. Most people who tell me they have “a couple cups” are well past 400 mg once we total it honestly.

  3. Check your blood pressure at home

    If you're a slow metabolizer, this is where it tends to show up first. A cuff and two weeks of morning readings cost almost nothing and tell you a great deal.

Find Out Which One You Actually Are

Caffeine is one small example of a much larger idea: your body is not the average of a study population. In a free 30-minute consultation we'll talk through what's worth measuring in your case — and what to do with the answer.