Rise and Grind


Caffeine is a constant presence on college campuses. It wakes students up in the morning and keeps them running long into the night. It comes in coffee, energy drinks and even supplements for a direct dose.

It is an integral part of many people’s morning routine, but the chemistry behind caffeine is anything but standard.

Behind the Bean

Molly Jean Henebury is a dietetic intern at Cornell University with a master's of science in nutrition and health promotion.

“Past the stomach we go into the small intestine. That’s where the caffeine is going to get absorbed. Once it’s there, it’s very sneaky. It takes on the shape of a neurotransmitter called adenosine,” Henebury explained.

“Past the stomach we go into the small intestine. That’s where the caffeine is going to get absorbed. Once it’s there, it’s very sneaky. It takes on the shape of a neurotransmitter called adenosine.”

Adenosine builds up in the body throughout the day. It’s the chemical responsible for that drowsy feeling people get when they stay awake for too long. The adenosine levels lower during sleep, so you wake up feeling refreshed in the morning.

“Caffeine is basically the twin of adenosine. It blocks the receptor, which means adenosine keeps building up without being noticed,” Henebury said.

Adenosine normally binds to receptors in the brain and slows down activity. This is what causes feelings of tiredness and a decreased heart rate when people are awake for long stretches of time.

When the caffeine fills the receptors, the adenosine has nowhere to go, and people don’t experience the ‘buildup of sleep’ they otherwise would.

At the same time, the chemicals norepinephrine and epinephrine — the latter being more commonly known as adrenaline — begin to build up in the body.

“Epinephrine and norepinephrine are vasoconstrictors, so they are going to make your blood vessels tighter and your blood pressure is going to go up,” Henebury noted.

When blood pumps quicker through the body, more oxygen makes it to the muscles and brain. This increase in blood flow is one of the mechanics responsible for the human ‘fight or flight’ response.

This tightening of the blood vessels is why caffeine is sometimes found in medicines, like Anacin, that prevent headaches. Constricting blood vessels in the brain can help stop vascular headaches.

Dopamine, the ‘reward hormone,’ also stays around longer when caffeine is in the system. According to the National Academies of Science, Engineering and Medicine, caffeine causes small amounts of dopamine to be released into the striatum, the part of the brain that governs decision-making, motivation and reward.

The most obvious benefit of caffeine is feeling more awake and alert, but consuming too much can negatively impact sleep and increase heart rate, which can be a stressor for anxiety and nerves.

How Much Is Too Much?

Scientists at the United States Food and Drug Administration (FDA) have cited 400 milligrams a day as an amount of caffeine that does not generally have negative or dangerous effects.

Even with that number in mind, it can be difficult to gauge exactly how much caffeine is in some drinks, especially when it comes to coffee. Even the way the beans are roasted can impact the caffeine content of the drink.

“When they’re baking the beans, if they leave them out longer, there’s less caffeine than in a ‘raw’ bean, backwards of what you would think,” Henebury explained. “Unless you’re in a [chemistry] lab and you can test it, you’re not really going to know how many milligrams of caffeine are in there.”

“Unless you’re in a [chemistry] lab and you can test it, you’re not really going to know how many milligrams of caffeine are in there.”

The FDA bases caffeine content on average ranges for certain types of drinks. The average eight ounce cup of coffee can contain about 80-100 milligrams of caffeine, while energy drinks can range anywhere from 40-250 milligrams of caffeine in the same size.

Drinking four to five cups of coffee a day can keep a person comfortably within the 400 milligram range, but drinking four to five energy drinks a day can put your anywhere from well under to nearly double that.

Adding another fold to the situation, the narrowing effect that caffeine has on the blood vessels can exacerbate pre-existing heart conditions if consumed to excess. If someone is already experiencing vasoconstriction because of an underlying condition, adding too much caffeine to the equation could make things worse.

Dehydration is also a factor to consider. Caffeine is a diuretic, which means people taking it will find themselves visiting the bathroom more frequently. A person could drink energy drinks all day, but their body won’t be getting the hydration it needs despite all the liquid coming in.

Increased Concentration

Caffeine can exist in more esoteric forms than just coffee or energy drinks. Caffeine supplements are branded to appeal to many different audiences, from “Genius Caffeine” to “MuscleTech 100% Caffeine Energy Supplements.”

Some of these energy supplement suppliers have found themselves in legal trouble for deceptive marketing. In 2014, Washington State Attorney General Bob Ferguson filed a lawsuit against Living Essentials, the makers of the popular energy drink 5-hour Energy.

Two years later, a judge ruled that Living Essentials had violated the Consumer Protection Act by manipulating surveys to suggest that doctors recommended their product, and that there was no evidence to support the company’s claim that the supplement’s “synergistic” interaction with caffeine made it superior to coffee.

In April 2018, the FDA warned consumers about dietary supplements containing pure or highly concentrated caffeine. While it can be difficult to gauge exactly how much caffeine is in a cup of coffee or a energy drink, misjudging a dose of pure, powdered caffeine is much more dangerous.

The difference between safe and toxic doses of highly concentrated caffeine is very small. According to the FDA, just one teaspoon of pure caffeine powder is roughly equivalent to 28 cups of coffee.

Erratic heartbeat, vomiting, disorientation and even seizures are all signs of a potential caffeine overdose, and the more concentrated the product the easier it can be to accidentally take too much.

Caffeine has upsides, as long as it is taken in moderation. Knowing what goes into the body helps people understand what they will be getting out of the product.