Caffeine: Are You Consuming Too Much?

Ah caffeine, one of the only drugs you have to explain NOT using. It's estimated that 85% of the U.S. population consumes at least one caffeinated beverage a day, with the majority coming in the form of coffee, tea, and soda. However, the increasing popularity of highly caffeinated energy drinks and preworkout supplements has contributed to an increased concern over “excess” caffeine consumption and its potential negative health effects. Many people have experienced the feeling of being uncomfortably "wired" on caffeine, so how much is too much?

Broadly speaking, the FDA, Health Canada, and European Food Safety Authority have all agreed that daily caffeine intake of 400mg or less is generally safe for most adults. While caffeine consumption is extremely widespread, an understanding of the caffeine content of common sources is not. Many people have no idea how much caffeine they actually consume, so to provide reference, 400mg of caffeine is equivalent to:

-16.6 servings of green tea

-4.2 servings of regular brewed coffee

-1 Venti Starbucks

-5.2 espresso shots

-5 Red Bulls

-2.5 Monster energy drinks (16oz)

-11 cans of Coke (12oz)

-2 5-Hour Energy shots

The reality is, most people are consuming far less than 400mg of caffeine per day. The U.S. Department of Health and Human Services estimates average caffeine consumption ranges from 110mg-260mg per day. So no, your two cups of joe a day are probably not going to give you a heart attack any time soon.

Ok, but what about the hardcore caffeinators? The coffee slammin', preworkout sippin', energy drink poppin' go-getters out there? The 400mg recommendation is based on "average" body size, but research gathered by the International Society of Sports Nutrition (ISSN) suggests a more individualized guideline of 6mg of caffeine per kilogram of body weight is safe for those with "normal" caffeine sensitivity.

That means if someone is 180lbs (82kg), their upper limit of safe consumption would be 491mg per day! So even if you love your preworkouts or go through more than one energy drink a day, you're likely still in the clear as far as an immediate cause for concern.

So What's the Big Deal?

With that said, is it really a good idea to be maxing out your caffeine quota each day? Probably not, and to understand why requires a better understanding of how caffeine functions in the body. The common conception is that caffeine "gives" someone energy, when that is simply not the case.

When we consume caffeine (most often through some type of beverage) it's quickly and easily absorbed into the bloodstream through epithelial tissue. In fact, 99% of caffeine is fully absorbed within 45 minutes of consumption. After absorption into the bloodstream it's transported to the liver, where it's broken down into three distinct compounds (theophylline, theobromine, and paraxanthine). However, some circulating caffeine does make its way to the brain, where it does some interesting things.

Caffeine molecules are similar in shape to adenosine, a neurotransmitter produced in the brain that has a direct effect on the sleep/wake cycle. When enough adenosine molecules bind to their receptor sites in the brain, we begin to feel tired and a signal is sent that it's time for sleep. Due to their similar shape, caffeine molecules bind to those same receptor sites, blocking adenosine from doing its job of making us feel sleepy. In short, caffeine is not "giving" someone energy out of thin air, it's simply blocking the tired signals from the brain.

Ever wondered why you feel addicted to caffeine? The blocking of adenosine receptor sites by caffeine also leads to an increase in dopamine release, which reinforces the compulsion to habitually consume more caffeine. This is part of why lack of motivation, fatigue, and difficulty concentrating are symptoms of caffeine withdrawal.

In addition, when excess adenosine cannot bind in the brain, it backs up in the bloodstream. This backup triggers the release of adrenaline from the adrenal glands. Chronically elevated adrenaline levels can lead to undesirable effects like weight gain, insomnia, and irritability. 

Other symptoms that could signal you're pushing your caffeine limit include:

-Headache

-Nervousness

-Frequent urination

-Rapid heartbeat

-Muscle tremors

The Bottom Line:

When kept in moderation, caffeine consumption poses little risk to most people. With that said, there is such a thing as consuming too much caffeine, too often. The dosages listed above represent guidelines that are appropriate for many, but your individual sensitivity to caffeine may vary based on genetic factors, medical history, and history of use.

Any time we are consuming an exogenous (outside) compound that affects our body chemistry there is cause for some degree of caution. In the case of caffeine however, when weighing potential benefits versus possible negative side effects, it's likely a net positive for most.