UF Study Finds Specialty Coffee’s Caffeine Content Capricious

Published: October 22nd, 2003

Category: Research

GAINESVILLE, Fla. — If that take-out coffee seems more invigorating than usual today, it might not be your imagination — it may be the java’s packing a bigger dose of caffeine than you expected, even if it’s decaf.

Scientists at the University of Florida College of Medicine recently analyzed 16-ounce servings of caffeinated coffee from specialty shops and found almost twice as much caffeine in the strongest brew – Starbucks regular, at 259 milligrams – compared with the weakest, Dunkin’ Donuts regular, at 143 milligrams.

Another type of Starbucks caffeinated coffee purchased from a single Gainesville store for several consecutive days varied even more, from 259 milligrams to a whopping 564 milligrams, almost as much caffeine as three maximum-strength NoDoz, said Bruce Goldberger, an associate professor and director of toxicology with UF’s department of pathology, immunology and laboratory medicine and an associate professor with the UF department of psychiatry’s division of addiction medicine.

And while some people may think they’re bypassing the stimulant, seven decaffeinated coffees from various shops all contained some caffeine, though less than 18 milligrams per 16-ounce serving.

The results are being presented today at the annual meeting of the Society of Forensic Toxicologists in Portland, Ore., and appear in the current issue of the Journal of Analytical Toxicology.

“I don’t think people really know that there is a wide range in (coffee’s) caffeine content,” said Goldberger, who led the study and is the editor of the journal. “Our experience with specialty coffee is that it is not consistent.”

But coffee drinkers may have to live with uncertainty, an important consideration for those who monitor their caffeine consumption, he said.

Caffeine can enhance human performance by increasing alertness and speeding reaction time, but it can cause increased heart rate, blood pressure and anxiety, according to previous research cited in the UF study.

The caffeine content of Starbucks coffee varies, according to a written statement provided by spokeswoman Lara Wyss in Seattle in response to a request for comment on the UF study.

Quoting from the statement: “We emphasize that any absolute numbers reported on caffeine levels in Starbucks coffee do not reflect what a customer would receive in every cup of Starbucks coffee. There are many variables that contribute to caffeine content from cup to cup,” including the type of bean, roasting and brewing methods, and grind.

Starbucks regular drip coffees contain an average of 200 milligrams of caffeine per 8-ounce serving; their decaffeinated drip coffees contain an average of 5 milligrams to 11 milligrams of caffeine per 8-ounce serving, according to the statement. A “frequently asked questions” feature on the Starbucks Web site indicated that the company intends to add caffeine-content information to the site in a future upgrade.

Caffeine is a stimulant that naturally occurs in more than 60 plants, including coffee, according to the International Food Information Council Foundation in Washington, D.C. The average American consumes about 200 milligrams of caffeine per day, mainly from coffee. An 8-ounce cup of drip-brewed coffee typically contains 85 milligrams of caffeine.

Moderate caffeine intake, defined as 250 milligrams per day, is not associated with any health risk, according to Medline Plus, a health information Web site maintained by the U.S. National Library of Medicine and the National Institutes of Health.

Though caffeine is recognized as an addictive substance, UF experts don’t usually encounter patients seeking help for caffeine dependence, said Dr. Mark S. Gold, a distinguished professor at UF’s McKnight Brain Institute and chief of addiction medicine in the psychiatry department.

“Caffeine dependence is a non-issue for me because people won’t leave their home for it, won’t mortgage their house for it, won’t choose caffeine over their wife,” said Gold, who recently co-authored a study on coffee’s caffeine content.

The UF study was conducted in two phases by Goldberger, toxicologist Edward Cone, of ConeChem Research in Severna Park, Md., and Rachel McCusker, a UF biological scientist. Funding was provided by Goldberger’s laboratory.

The first phase included a one-time purchase of 14 caffeinated brewed coffees from six retailers in Bethesda and Severna Park, Md., including Starbucks, Dunkin’ Donuts, Big Bean, Hampden Café, Royal Farms and Einstein Bros. Six espressos and seven decaffeinated brewed coffees also were purchased. Caffeine was isolated from samples of coffees using chemical and mechanical treatments, then measured by gas chromatography.

The espressos ranged in size from 40 milliliters to 170 milliliters and contained 58 milligrams to 185 milligrams of caffeine, with the larger servings containing more caffeine.

The decaffeinated coffees all contained less than 18 milligrams of caffeine per 16-ounce serving. The U.S. Food and Drug Administration currently does not require decaffeinated coffee to be absolutely caffeine-free, an agency spokesperson said.

The study’s second phase used 16-ounce cups of Starbucks’ Breakfast Blend, a mix of Latin American coffees, purchased on six consecutive days from a single Gainesville store and analyzed by the same method. Results for the six days were, in order: 564 milligrams, 498 milligrams, 259 milligrams, 303 milligrams, 300 milligrams and 307 milligrams.

The study results demonstrate the need for retailers to inform consumers of the caffeine content in ready-to-drink coffee because many of the beverages contain so much, said Michael F. Jacobson, executive director of the Center for Science in the Public Interest in Washington, D.C.

“Until now the focus has been on coffee packages, but this study indicates the need to have caffeine-content information at coffee shops as well,” Jacobson said.


Tom Nordlie, newsdesk@ufl.edu

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