The Chemistry of Your Cup

What’s in my Cup of Coffee?

Reuters reports that a 2018 National Coffee Association’s survey shows Americans are drinking more coffee than they have in years. We break down what’s in your daily cup of coffee and the effects of coffee and caffeine on your health.

By Camille Platt


Did you know black coffee is about 98.75% water? You can even count it toward your daily fluid intake. And with no carbs and no sugar, it far surpasses energy drinks, soda, juice, or sweet tea as the best option for an extra boost. The average energy drink has around 30 grams of added sugar – so even if you do add a teaspoon of sugar, coffee is still the better option. It’s easy to think so because it acts as a short-term diuretic (i.e., it causes the need to urinate), but coffee only dehydrates you if you overdo it. Studies have shown you can drink up to five cups of coffee without becoming dehydrated.


This compound is the most widely used mood-altering drug in the world. Caffeine stimulates the central nervous system by blocking the chemical adenosine in the brain. Since adenosine makes you sleepy, the end result is a short-term lift in your mood, reaction time, and overall vigilance. Caffeine can also increase your metabolic rate by up to 11%.

How much is too much: According to the Mayo Clinic, up to 400 milligrams of caffeine a day is safe for most adults. That equates to roughly four cups of coffee. Any more can cause restlessness, upset stomach, irritability, nervousness, muscle tremors, and insomnia.

How to know if you’re addicted: If missing your morning cup leaves you feeling like a wreck, you may be too dependent. Some of the most common withdrawal symptoms are headaches, sleepiness, lethargy, irritability, brain fog, depression, and difficulty concentrating.

How to quit: To make it easier on yourself, don’t go cold turkey. Begin phasing out caffeine in stages, cutting out one cup of coffee per day. Since your brain has changed its chemical makeup, fitting the caffeine neatly into cell receptors where adenosine should be, a full reset can take up to 12 days.

Natural Oils

Coffee contains the fat-soluble compounds cafestol and kahweol, also called diterpenes. In high consumption, diterpenes can raise your levels of total and LDL (bad) cholesterol. The good news is that these compounds can be retained in a paper filter.

How to avoid: If you have high cholesterol, stick with filtered coffee, as opposed to drinking espresso or using a French press or percolator. Unfiltered coffee, such as coffee made in a French press, has been found to increase LDL cholesterol levels by 10% or more.


As an important source of disease-fighting antioxidants, coffee can help reduce inflammation in the body. Overall, the antioxidants in coffee can be linked to better control of asthma symptoms, diabetes protection, a lower risk of gastrointestinal disease, improved heart health, and protection against neurodegenerative diseases like Alzheimer’s. Among the many antioxidants in coffee are chlorogenic acids (CGAs), which give coffee its distinct bitter flavor.

How they affect taste: When roasted, the CGAs in the coffee bean decompose into caffeic and quinic acid, retaining about half of the original CGAs in the amount of time it takes to achieve a medium roast. The higher the level of caffeic and quinic acid, the darker the roast and the more bitter the taste.

More than 50% of all U.S. adults drink coffee every day. Here’s how it changes your body within the first hour of draining your mug.

Your Muscles

Caffeine slows the depletion of a type of sugar called glycogen (essentially, muscle fuel), so a single cup of coffee can help you exercise for a third longer than usual. One study published in the International Journal of Sport Nutrition and Exercise Metabolism found a cup of caffeinated coffee within an hour before exercising can help you burn 15% more calories in the three hours following the workout.

Your Eyes

Caffeinated coffee activates your body’s “fight-or-flight mode” by triggering the release of adrenaline. This adrenaline, in turn, dilates your pupils and causes a temporary sharpening of vision.

Your Brain

After about 30 minutes of drinking a cup of coffee, you begin to feel more alert and focused as the caffeine begins to block adenosine. At the same time, it boosts various other neurotransmitters in your brain.

Your Teeth

While too much can stain your pearly whites and—let’s face it—wreck your breath, coffee has been shown to kill bacteria and oral plaque. But here’s the catch: you can’t add sugar, syrups, or milk. Why? When the chemicals in coffee dissolve the plaque, it gives those extra add-ins full access to the crevices between your teeth. This puts you at greater risk for cavities and decay.

Your Bowels

Since coffee speeds up digestion
and can have a bit of a laxative effect, it can leave you with an urge to run to the bathroom. It can also exaggerate symptoms of irritable bowel syndrome, Crohn’s Disease, colitis, gastritis, and other uncomfortable bowel conditions.

Your Stomach

Coffee can stimulate digestion by increasing the acidity in your stomach.  However, habitual coffee drinking—especially when done on an empty stomach—can lead to gastroesophageal reflux disease (GERD), a condition in which stomach acid travels back up to the esophagus and causes discomfort or pain.

Your Heart

Coffee’s most immediate effects on the body are cardiovascular. Within 15 minutes, your blood pressure elevates by 10 to 15% (although the exactness of this number depends on your weight, how much food you’ve eaten, and whether you are a regular coffee drinker).