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Caffeine: How Much Is Too Much?



With assistance from Northeastern graduate student Patrick H. Norwood

Caffeine is the single most widely used substance in the world over, regardless of age group or cultural background. It is known as a common stimulant. We find it in a variety of foods, including coffee, tea, soda, and chocolate. Given its popularity and social acceptance, many of us come to enjoy at least a modest serving in our daily lives; Americans consume an average of 300 mg per day -- the equivalent of about 2 medium cups of brewed coffee. What, if any, are the health implications of caffeine consumption? And what if, rather than 1 or 2, we drink 5 or 6 cups of coffee each day? Are there major concerns to be had?

The short answer is "No." Having a few cups of coffee throughout the day yields nearly the average intake. However, with that said some people may experience a particular hypersensitivity to caffeine even at moderate levels, in which case they may do better by avoiding it. Others, however, may have a naturally (or developed) tolerance that allows for moderate consumption.

Many people seek out caffeine for physiological or psychological effects, which typically include increased alertness, increased energy, and improved mood. These effects are typically noticed after consuming the standard low-to-moderate dose (200-300 mg), matching the average daily intake. Of course, exaggerated, these same effects can become quite uncomfortable, including:
  • Excessive heart rate and/or tremors
  • Restlessness
  • Delayed sleep
  • Irritability
  • Anxiety
In these cases, the same results originally sought out can become rather unpleasant. However, in most individuals, such dramatic results are not typically seen unless consuming 400-500 mg or more. To put this caffeine consumption in perspective consider the following table, which attempts to illustrate the relative quantity of caffeine in popular sources (e.g. coffee, assorted energy drinks), and what would be required to achieve a cumulative 400 mg.

Source
Caffeine per serving (mg)
Approximate servings to reach 400 mg
Red Bull (energy drink, 8 fl. oz.)
80
5
Diet or regular Coke/Pepsi (16oz.)
50-63
7- 8
AMP (energy drink, 16. fl. oz)
143
3
Monster (energy drink, 16 fl. oz.)
160
2.5
Dunkin' Donuts coffee (16 fl. oz.)
206
2
5 Hour Energy (energy drink, 2 fl. oz.)
220
2
Starbucks coffee (16 fl. oz.)
320
1.25

As listed above, approaching the upper limits of caffeine tolerance (for most) is not something accomplished in error; it takes five 8 oz. Red Bull energy drinks to reach the conservative threshold of 400 mg! Most of us can rest easy in the knowledge that we will not experience such unpleasant side effects under normal conditions.

What if it is a regular habit? For a healthy individual, caffeine typically has only a short-term impact on blood pressure; the increase is temporary, as caffeine is a stimulant that increases heart rate and inspires other similar physiological responses. The Mayo Clinic advises that those with known high blood-pressure, overweight individuals, or those older than 70 years of age should discuss their caffeine consumption with a physician.

In moderation, it can be a safe addition to the diet of an otherwise healthy individual. The following can be useful in avoiding overuse:
  • Be aware of your own caffeine sensitivity; find what amount, if any, feels right for you
  • Moderate consumption (e.g. 200-300 mg per day, depending on tolerance)
  • Avoid dehydration (i.e. don't subsist solely on coffee -- that's no good!)
With this in mind, it seems that most people can enjoy a bit of caffeine without much concern during the day!

-------------------

Patrick H. Norwood is a graduate student of nutritionist Christine Clark in the MS in Applied Nutrition program through the College of Professional Studies at Northeastern University.

Nutritionist Christine Clark works with Dining Services to provide you with tips and techniques to stay healthy during your time at Northeastern. If you have any further questions about this topic or are looking for more information about any other nutrition or diet topic, such as food allergies or sports nutrition, please contact her at christine.clark2@compass-usa.com or call UHCS at 617-373-2772 for an appointment.

References:
  1. Chawla J, Suleman A, Lorenzo N. Neurologic Effects of Caffeine. Medscape. http://emedicine.medscape.com/article/1182710-overview. Updated August 12, 2013. Accessed October 12, 2013.
  2. Caffeine Consumption Among Children and Adolescents. National Council on Strength & Fitness. http://www.ncsf.org/enew/articles/articles-CaffeineConsumptionChildrenAdolescents.aspx. Accessed October 11, 2013.
  3. Caffeine Intake by the U.S. Population. Food and Drug Administration. http://www.fda.gov/downloads/AboutFDA/CentersOffices/OfficeofFoods/CFSAN/CFSANFOIAElectronicReadingRoom/UCM333191.pdf. Published September, 2009. Accessed October 12, 2013. Updated August, 2010.
  4. Caffeine: How does it affect blood pressure? Mayo Clinic. http://www.mayoclinic.com/health/blood-pressure/AN00792. Published October 21, 2011. Accessed October 13, 2013.
  5. Freedman ND, Park Y, Abnet CC, Holenbeck AR, Sinha R. Association of Coffee Drinking with Total and Cause-Specific Mortality. N Engl J Med. 2012;366(20):1891-1904.
  6. Silverman K, Evans SM, Strain EC, Griggiths RR. Withdrawal Syndrome After the Double-Blind Cessation of Caffeine Consumption. N Engl J Med. 1992;327(16):1109-1114.
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