MONTGOMERY, Ala. (AP) – A new study shows that citrus-flavored sodas often have a higher caffeine content than the most popular colas. The research also found that caffeine content can vary widely from brand to brand, and even within a brand.

The researchers – along with consumer advocates – say labels on packaging should give the caffeine content to help buyers make informed choices. While most cans and bottles of soda don’t give caffeine amounts, some national brand beverage companies are already heading in that direction.

“I don’t really take a stand on whether caffeine is good or bad, but I do think the consumer has a right to know what they’re getting,” said Leonard Bell, one of two food researchers who conducted the study at Auburn University.

The Food and Drug Administration does not limit the amount of caffeine in foods. FDA spokeswoman Veronica Castro said a 0.02 percent caffeine content is generally recognized as safe for cola-type beverages.

For a 12-ounce soft drink, that’s about 72 milligrams of caffeine.

The study by Bell and co-author Ken-Hong Chou found caffeine content in 12-ounce sodas ranged from 4.9 milligrams for a store brand of cola to 74 milligrams in Vault Zero, a citrus drink.

David Schardt, senior nutritionist at the Center for Science in the Public Interest, said the Washington-based nonprofit first asked the FDA 10 years ago to require that food and drink labels show the caffeine content.

“People should be able to monitor their intake and to make informed choices because it can affect their sleep and can make some people jittery,” Schardt said.

Rather than deterring shoppers, labeling might have the opposite effect on those seeking more caffeine, he said.

The FDA has received a number of petitions to include caffeine content labeling on products, including the 1997 request from the consumer group, according to Mike Herndon, another FDA spokesman.

The Coca-Cola Co., based in Atlanta, and Purchase, N.Y.-based PepsiCo Inc. said they are phasing in new labels that include caffeine content. Most national brands also provide lists of the amount of caffeine in their products on their Web sites.

“It’s really in our best interest and that of our consumers to provide that info,” said Diana Garza, a Coca-Cola spokeswoman.

While caffeine occurs naturally in some products, like coffee and tea, it’s an additive in soft drinks. It is commonly sought out for its stimulatory effect, and beverage companies say the slightly bitter substance is also an element in their flavor formulas.

“The addition of caffeine in a beverage is largely as a flavoring,” Garza said.

Bell and Chou say the buzz caused by caffeine is its main draw. They said previous research showed that only 8 percent of adults were able to differentiate between the taste of caffeinated and caffeine-free colas.

Their study analyzed the caffeine contents of 56 national brand and 75 store brand carbonated drinks. It was published in the August issue of the Journal of Food Science.

Caffeine content of well-known national brands include: Coca-Cola (33.9 milligrams), Diet Pepsi (36.7 milligrams), Pepsi (38.9 milligrams), Dr Pepper (42.6 milligrams), Diet Dr Pepper (44.1 milligrams), Diet Coke (46.3 milligrams), Mountain Dew (54.8 milligrams) and Diet Mountain Dew (55.2 milligrams).

By comparison, according to the American Beverage Association Web site, a 12-ounce cup of coffee has between 156 and 288 milligrams of caffeine, and the same amount of tea has 30-135 milligrams.

Bell said the data provided by manufacturers of national brand soft drinks was consistent with the findings of his study. He said the caffeine data for store brand drinks is not easy to find and often isn’t available at all.

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On the Net:

Center for Science in the Public Interest http://www.cspinet.org/

American Beverage Association http://www.ameribev.org