Both medical and public opinions on coffee — and specifically the compound that’s behind its enduring popularity, caffeine — have swung back and forth dramatically for centuries. For an interesting tour through the historical coffee debate, check out this CNN article.
At the moment, experts agree that consuming a reasonable amount of caffeine (up to 400mg, or roughly three to four 8-ounce cups of coffee) has no harmful health impacts on most people. They do caution, however, that drinking a lot of coffee has been linked to increased risk of premature births and stillbirths, so pregnant women should stick to no more than one cup a day. Studies have indicated that drinking coffee may provide health benefits ranging from better cardiovascular health and reduced risk of Type 2 diabetes to a longer life.
But, that all being said, the fact is that caffeine is a chemical that’s having a pronounced effect on your body every time you consume it. So, putting aside the centuries-old roller coaster of debate, let’s take a look at what we actually know about how and why caffeine affects you.
Caffeine is a drug
Caffeine has been called “the most popular psychoactive drug in the world,” a dubious-sounding distinction it shares with alcohol. It is a naturally occurring substance that can be found in over 60 plant species worldwide. The most common sources used by humans include coffee beans, tea leaves, kola nuts (used to flavor cola drinks), and cacao pods (used to make chocolate). Synthetic caffeine has also been developed for use in medicines and as a food additive in popular “energy” products.
Caffeine is classified as a central nervous system stimulant of the methylxanthine class. Because it is both fat- and water-soluble, it readily crosses the blood-brain barrier where it produces its famous effects by blocking adenosine receptors — essentially becoming a roadblock to the brain’s normal shutdown mode.
By interfering with some of the chemical processes that make you sleepy, caffeine temporarily tricks the brain into thinking it’s not so tired after all. But, it doesn’t just keep you from sleeping. It’s a stimulant, so it actually reverses the process by exciting neural activity, which most people experience as mental clarity and a lifting of the “brain fog” that often accompanies exhaustion. It also causes blood vessels in the brain to constrict instead of dilating as they do when you’re preparing to sleep. This effect can help relieve some types of headaches, which is why caffeine is paired with mild pain killers in over-the-counter drugs like Anacin and Excedrin.
It also increases the production and release of other chemicals and neurotransmitters in the brain, two being dopamine (the “reward” chemical that is responsible for that little happy dance you sometimes do in the car) and serotonin (the “feel good” chemical that serves as the brain’s natural antidepressant.)
Caffeine’s stimulating effects go beyond the brain, too, as the blocking of adenosine receptors sets off a powerful chain reaction. The pituitary gland interprets increased neural activity as a sign of potential danger, so it activates the “fight or flight” response, flooding your bloodstream with adrenaline. As a result:
- Your pupils dilate
- Your airways open wider
- Your heart rate increases
- Blood flow near the surface decreases
- Blood flow to the muscles increases
- Blood pressure rises
- Your liver releases sugar into the bloodstream for an added boost of energy
Everything happening here is designed to give you the best chance of outrunning or otherwise surviving an encounter with whatever wild animal just appeared in your paleolithic cave. You can see better in low light, you’re less likely to bleed to death, and more likely to have the speed and agility needed to fight or flee.
Of course, when you’re sipping coffee while sitting at your desk and typing an email, you just register all those effects as “that little pick-me-up” you needed.
Yes, you are addicted
As is the case with many drugs that produce a pleasurable effect, caffeine is habit-forming, physically, mentally, and emotionally. And, like other addictive substances, many people need to consume more over time to achieve the same effects they used to get with a smaller dose.
As addictive drugs go, however, caffeine’s hook is very mild. If you usually start your day with one or two cups of coffee and something prevents you from doing so tomorrow, you’ll probably notice a headache around the forehead and temples within an hour or two of your normal daily “hit”. You’ll feel groggy and possibly irritable as well. But, that’s usually as far as it gets. And, if you decide to forego coffee from then on, you’ll most likely get past withdrawal within a week.
There is such a thing as too much
While it’s not easy to do by drinking coffee, it’s definitely possible to overdose on caffeine if you combine various sources throughout the day. Caffeine pills are especially dangerous because of their concentration. It’s important to note that caffeine has a half-life of about six hours. So, if you consume 200mg of caffeine at 8:00 am, you still have roughly 100mg in your system at 2:00 pm. That’s why some people have difficulty sleeping if they drink a cup of coffee anytime after mid-afternoon.
As with all drugs, the amount required changes based on body weight. The lower the body weight, the less of the drug it takes to cause damage. So, children and underweight adults are especially vulnerable to caffeine overdose.
More than 150-200 milligrams of caffeine per kilogram of body weight is considered lethal. For a 100-pound child or young adult, that comes out to about 9 grams of total caffeine. That would require drinking upwards of 45 cups of coffee or roughly the same number of caffeine pills. Double that for a 200-pound adult, and that explains why it’s so rare.
However, consuming just 3 milligrams per kilogram of body weight beyond the recommended daily intake (about 400mg for an adult, less for a child) can produce adverse results. To put this in perspective, our 100-pound teenager would exceed the adverse-effect level by drinking just one energy drink or energy shot after having had a cup of coffee. It’s very easy to do this with caffeine pills if you take more than the stated dose.
Drinking coffee has real health benefits
Most of the studies exploring the effects of caffeine have used coffee as the medium because it’s the overwhelming favorite among significant sources. Likewise, studies investigating the health benefits of drinking coffee generally use caffeinated coffee. So, it’s actually difficult to determine which positive benefits derived from the caffeine and which can be traced to other components in coffee.
Studies have shown that drinking caffeinated coffee can help relieve pain, reduce or relieve migraine headaches, reduce asthma symptoms, and elevate mood. As a mental stimulant, it increases alertness, cognition, and reaction speed. Because it combats fatigue, it improves performance on tasks that require vigilance like driving, flying, solving simple math problems, and data entry.
Studies also indicate other impressive benefits:
- 80 percent drop in risk of developing Parkinson's disease
- 20 percent drop in risk for colon cancer
- 80 percent drop in the chances of developing cirrhosis
- 50 percent drop in the risk of developing gallstones
Mice who received high doses of caffeine were protected from developing Alzheimer’s disease and saw a reduction in precancerous cell division. And, as noted earlier, many studies suggest that a daily coffee habit can even help you live longer.
As is the case with all nutritional guidelines, moderation is the key. There’s nothing wrong with enjoying your morning java and appreciating the jolt of energy and alertness it provides. Just monitor your reaction, make sure the habit isn’t interfering with proper sleep, and that it doesn’t become a vehicle for tons of extra calories you’re not accounting for. In the end, (unless they suddenly discover something brand new tomorrow,) you can do so guiltfree.