Is Coffee “Cold” or “Warm”? Why It Makes Some People Jittery (and How to Find Your Perfect Cup)

 When people try coffee for the first time, reactions usually fall into two camps: some feel warm all over after a cup, while others get a cool, almost refreshing sensation. That curious difference has sparked countless discussions—so is coffee “cold” or “warm” in nature?

Even more puzzling: one person drinks a small afternoon cup and then lies awake until dawn, while another can drink right after dinner and fall asleep instantly. To understand why, we need to look at the subtle ways coffee interacts with the body.

The Nature of Coffee: What Is It, Really?

From the perspective of traditional Chinese medicine, coffee is considered a warming beverage. It can boost circulation and stimulate the central nervous system—which is why many people feel physically warmer after a hot cup on a chilly morning.

Modern science, however, shows another side of coffee. Caffeine is a natural stimulant that temporarily increases metabolic rate, producing more body heat—this is its “warming” effect.

At the same time, coffee contains various organic acids, like chlorogenic acid and quinic acid, which may exert mild “cooling” effects in the body. This apparent contradiction helps explain why people with different constitutions experience coffee so differently.

Why Does Coffee Make You Feel Jittery?

Many people have experienced the heart-racing, hand-shaking, anxiety-like reaction that coffee can trigger. Biochemically, this is a clash inside the body.

Caffeine’s molecular structure closely resembles that of adenosine. Normally, adenosine binds to receptors in the brain and signals drowsiness—telling your body it’s time to rest. Caffeine, however, jumps in and blocks those receptors, preventing adenosine from doing its job.

As a result, the brain doesn’t get the “tired” signal and the adrenal glands release more adrenaline. That adrenaline speeds up the heart, raises blood pressure, and opens airways—preparing the body for a fight-or-flight response. For some people, that stress response is overly strong, showing up as palpitations and tremors.

Are You Sensitive to Caffeine?

Why do two people react so differently to the same cup of coffee? The key lies in individual differences in caffeine metabolism.

An enzyme called CYP1A2 metabolizes caffeine in the body, and its activity level is largely genetically determined. If your CYP1A2 activity is low, caffeine stays in your system longer and its effects are stronger—half a cup could keep you awake all night. Conversely, if your CYP1A2 activity is high, you might be able to drink coffee at night and still sleep fine. Genetic variation explains much of the ~95% difference in how quickly people metabolize caffeine, and it largely determines whether you’re caffeine-sensitive.

Coffee’s Effects Go Beyond Caffeine

While caffeine plays the lead role, coffee’s effects on the body are more complex. Coffee contains over 1,000 bioactive compounds that together shape its personality.

Polyphenols like chlorogenic acid act as antioxidants, reduce inflammation, and protect blood vessels. Compounds such as cafestol and kahweol can influence cholesterol metabolism. Trace minerals—magnesium, potassium, and others—also affect physiological responses.

These compounds interact in synergistic and sometimes opposing ways, which is why different bean varieties, roast levels, and brewing methods can produce markedly different effects in the same person.

How to Find the Right Way to Drink Coffee for You

Because responses to coffee vary so much, try these practical tips to discover what suits you best:

• Notice your reactions. After drinking coffee, do you feel alert or anxious? Comfortable or uncomfortable in your stomach? Track these responses and adjust dosing accordingly.

• Choose the right coffee. Dark roasts often contain slightly less caffeine than light roasts because some caffeine breaks down during roasting. Dark roasts also produce more N-methylpyridinium, which helps reduce stomach acid—making them gentler on the stomach for some people.

• Time your cups. Cortisol, a natural wakefulness hormone, typically peaks around 8–9 AM and has a smaller peak near 1 PM. Drinking coffee between those peaks often yields the best effect.

• Pair coffee with food. Coffee temporarily affects blood sugar regulation; drinking it with food can smooth that effect. Also stay hydrated—coffee has a mild diuretic effect.

• Start small. If you’re sensitive to caffeine, begin with a half cup and let your body adapt gradually.

Coffee is a personal relationship. Some liken it to making friends—you need time to learn each other’s rhythms and boundaries. Your experience with coffee today may differ from yesterday because your body’s state is always changing.