A study published in January 2014 involving over 40,000 people defines beverage caffeine intakes in the US, revealing the amounts of caffeine consumed and from what source per age group. As your Green-Eyed Guide, I’m going to explain what it all means.

The following is a scientist to non-scientist translation of the article “Beverage caffeine intakes in the U.S.”, published in Food and Chemical Toxicology 63 (2014) 136-142, which is available HERE.


Thirty-Second Overview

  1. Goal = Assess beverage* caffeine intakes in US population age 2 and up*
  2. Who = Nutrition Sciences Dept at Penn State and 42,851 study participants*
  3. How = 7-Day Diaries of all beverages consumed*
  4. When = 1 year from October 2010 through September 2011*
  5. What = Findings*:
  • 85% of the population consume at least 1 caffeinated beverage per day
  • People age 50-64 consume the most caffeine, averaging 226 milligrams per day
  • Less than 10% of all caffeine consumers drink energy drinks

Green-Eyed Insight: Details(*) that Make a Difference

Any time you read a science journal article, remember that top paragraph is called an “Abstract” because IT’S NOT THE WHOLE PICTURE. Notice all those asterisks in the Thirty-Second Overview? Lawyers call it “fine print”; I call it “triggers for analytical thinking”. One by one, let’s consider the details that make a big difference.

Note this can from my collection uses a Supplement Facts panel - this product has been reclassified as a beverage so current products feature a Nutrition Facts Panel, and the label has been updated to say 1 Serving per Container.
Note this can from my collection uses a Supplement Facts panel – this product has been reclassified as a beverage so current products feature a Nutrition Facts Panel.

1*: Energy drinks with “Supplement Facts” panels are not considered “beverages”, but they are still counted in this “Beverage Caffeine Intake” study. Caffeine-containing fruit juices, flavored waters and sports drinks were all counted in the “energy drink” category.  What ISN’T counted at all is the caffeine from medication, pills or food like dark chocolate.

RELATED READING: Monster Energy Switches from Supplement to Beverage and What That Means and Why Putting Caffeine in Gum is a Bad Idea

1*continued: Parents filled out the diaries for study participants under age 12. This isn’t an issue for those under age 6 but what about those between age 6 and 12? When you were that age, did you ever tell your parents what they wanted to hear instead of the truth? (Confession: I still do that sometimes)

It’s possible some of these 6-12 year olds stop at the 7-11 en route to school and buy beverages their parents have no knowledge about. It’s difficult to say how this “minor problem” affects the accuracy of the beverages reported for this age group, but it’s something to keep in mind as we review the rest of the data.

2*: Penn State got 42,851 surveys but they reported the response rate at approximately 15%. That means 17 out of 20 people they asked refused to participate, even though they’d be given monetary compensation for completing the survey.

Sleepless.and.StressedThe Million Dollar Question – How many people opted not to participate because they felt they’d be too busy? Aren’t those “super-busy” people most likely to consume caffeine?  Again, this isn’t tangible or credible criticism; it’s just something to think about as we review the rest of the data.

3*: If someone in the study left any days blank or reported less than 21 entries total, their information was not counted. That might seem harsh but stop and think how many times in 7 days you consume liquids. Even if you only ever consume water and nothing else, water at breakfast, lunch and dinner is 3×7=21. This survey requirement is crucial because it limits the risk of incomplete surveys skewing the results.

4*: The surveys were sent out in waves so data was collected over a whole year. This staggered timing is important to minimize any seasonal bias of where people are getting their caffeine (i.e. from hot coffee in winter; from ice-cold soda in summer). The dates are also important to note because news stories about caffeine can have a dramatic effect and change otherwise normal caffeine consumption habits. Note: the Four Loko Incident in Washington state occurred October 2010; Anais Fournier passed December 2011.

5*: Findings in the abstract are considered the most important, the most relevant or the most interesting. However, with a population study like this there’s a plethora of useful consumer data so it’s well-worth the time to dig through the details.

To Be Continued – Green-Eyed Guide reviews the rest of the data in this study and explains:

1-The Battle of the Sexes: Caffeine Consumption by Gender

2-Coffee Inconsistencies: What You Don’t Know About Joe

3-Decepticon: Deceptive Contents of a Data Table

4-Analysis Paralysis: What To Do When All the Info You’ve Ever Dreamed of is in One Handy Chart

5-Key Takeaways: Truly Understanding Caffeine Habits for Tweens, Teens and College Kids