Have you ever had a late-night study session with your friend where you both grab a cup of coffee? You finish your quad-shot Americano expecting to get a productivity boost. Instead, your friend is energized and focused, while you’re jittery, anxious, and eventually staring at the ceiling at 3 a.m. The next morning, they ace their exam, yet you can barely keep your eyes open, your head goes blank, and you struggle through the test. So why did the same cup of coffee affect you so differently? The answer lies not only in the chemistry of your coffee, but also in the biology of you and your friend.

To understand why coffee affects us differently, we first need to look inside the cup. Coffee contains hundreds of chemical compounds, including caffeine (1,3,7-trimethylxanthine), trigonelline, which contributes to the bitterness, chlorogenic acids (CGAs), and various molecules that contribute to its characteristic flavor and aroma (Saud & Salamatullah, 2021). However, the chemistry of coffee does not start and end with the bean itself. During roasting, heat triggers reactions such as the Maillard reaction, a chemical process between amino acids and reducing sugars, as well as the degradation of naturally occurring compounds. These processes produce many of the volatile molecules that are responsible for the distinctive smell and taste of coffee (Pajuelo-Muñoz et al., 2026). Out of all these compounds, caffeine is particularly important for its effects on the brain. Rather than directly providing energy, caffeine acts as an adenosine receptor antagonist, competitively occupying A1 and A2A receptors (A2AAR) and preventing adenosine from exerting its usual effects (Do et al., 2021). Since adenosine accumulation naturally promotes feelings of fatigue and sleepiness, blocking its signaling reduces the perception of tiredness and promotes alertness instead (Reichert et al., 2022). Long story short, your coffee does not necessarily give your brain more energy; it temporarily makes it harder for your brain to notice that it is tired.

But if caffeine interacts with the same adenosine receptors in everyone, why can its effects vary so much from person to person? Part of the answer may lie in our genes. One important gene is CYP1A2, which encodes cytochrome P450 1A2, a liver enzyme that metabolizes about 95% of the caffeine you consume (Mahdavi et al., 2023). Genetic variation in this gene can contribute to differences in how quickly caffeine is broken down and cleared from the body. For example, the AA genotype of the CYP1A2 rs762551 variant has been associated with higher CYP1A2 activity and faster caffeine metabolism compared with AC or CC genotypes, although this relationship is also influenced by environmental factors like smoking (Popa et al., 2025). In general, people who metabolize caffeine more slowly may maintain higher caffeine concentrations for longer and may be more likely to experience effects such as jitteriness or sleep disruption after consuming caffeine.

While CYP1A2 influences how quickly your body clears caffeine, another gene, ADORA2A, encodes the adenosine A2A receptors involved in caffeine’s effects on the brain. Variations in this gene have been associated with differences in psychological responses to caffeine, including anxiety and sleep disruption (Rahimi et al., 2024). For instance, studies of the ADORA2A rs5751876 variant have found that individuals with the C/T or T/T genotypes had a lower risk of sleep complaints compared to C/C carriers, particularly among moderate caffeine consumers (Erblang et al., 2019). Nevertheless, our DNA is only one piece of the puzzle. The amount of caffeine consumed, habitual coffee consumption, medications, smoking, age, and individual physiology can also influence how long caffeine remains in our body and how strongly we experience its effects (Rauf et al., 2025). Therefore, your response to coffee is not determined by a single “coffee gene”; it is the result of genetics interacting with the environment and your individual biology.

If our biology can influence how we experience coffee, what about the coffee itself? Biotechnology raises an interesting question: could we engineer coffee to better suit different needs? One example is the development of low-caffeine or caffeine-free coffee. Caffeine is produced through a series of biosynthetic reactions in which enzymes called methyltransferases progressively methylate xanthine-related compounds, ultimately producing caffeine (Jiang et al., 2025). Leibrock et al. (2022) identified XMT and DXMT, which encode enzymes involved in successive methylation steps of caffeine biosynthesis, as potential targets. By using CRISPR-Cas to knock out one of these genes, the pathway could be disrupted, thereby reducing or potentially preventing caffeine production in the coffee bean. The researchers proposed introducing the CRISPR-Cas system into coffee cells through Agrobacterium tumefaciens-mediated transformation, although producing a commercially viable caffeine-free coffee plant would still require further development. Aside from caffeine, biotechnology could also modify flavor-associated metabolites, such as sugars and aroma compounds, while controlled fermentation using selected microorganisms, such as Saccharomyces yeasts or Lactobacillus bacteria, could similarly alter the compounds that shape the final flavor profile (Todhanakasem et al., 2024). In this way, “better coffee” does not necessarily mean stronger coffee; it could mean coffee with characteristics designed for a specific purpose.

So, what would the perfect cup of coffee look like? Would it have no caffeine, or have a specific flavor profile designed around your preferences, or just enough caffeine to keep you awake without making you question every life decision? Could we eventually produce beans with greater consistency, plants that are more resilient to our changing climate, or coffee specifically tailored to different physiological responses? Perhaps the future of coffee is not about finding one “perfect” cup, but creating coffee that works better for different people and purposes. From the chemistry of the bean to the biology of the drinker, biotechnology could help us understand, and eventually shape, what makes coffee work differently for each of us. So the next time your friend orders a triple-shot espresso and sleeps like a baby while you’re wide awake at 3 a.m., remember: “Maybe it’s not the coffee, maybe it’s your DNA.”

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