Soda drinkers may be alarmed by a new study by Consumer Reports that shows that high levels of caramel coloring in some products may cause cancer, but medical experts say people need to put the warnings in perspective.
The magazine's investigation suggests that a "potentially carcinogenic" chemical – 4-methylimidazole (4-MEI) – is present in certain popular soft drinks at concerning levels. The investigation was sparked by a 2012 law in California that requires companies to label products that contained more than 29 micrograms of 4-MEI.
"I don't recommend that people drink a lot of soda," said Dr. Richard Besser, ABC's chief medical correspondent. "You have an occasional soda, it doesn't matter which one you have. You'll be fine."
The chemical, 4-MEI, gives some sodas its brown coloring and is, according to the Food and Drug Administration, "an impurity found in some caramel coloring at low levels during the manufacturing process."
In 2007, a federal government study concluded that 4-MEI caused cancer in mice and the International Agency for Research on Cancer determined the chemical to be "possibly carcinogenic to humans" in 2011, according to Consumer Reports.
Kenneth Portier, managing director for statistics and evaluation at the American Cancer Society, said that the International Agency for the Research of Cancer has assessed 4-MEI as "possibly carcinogenic" based on animal studies.
"There is no direct evidence that the chemical has health effects in humans, and scientists have yet to figure out how 4-MEI produces lung tumors in mice, limiting our understanding of the risk, and whether it applies to humans. This lack of strong scientific knowledge is actually pretty common for suspected food-borne carcinogens, and does not mean there is not a risk; just that we don't know enough at this point to say that there is."
While the American Cancer Society monitors the risks of "trace carcinogens" in food, Portier said that smoking, obesity and lack of physical activity are the greatest known risks for the disease.
Consumer Reports tested levels of the chemical 4-MEI in a total of 100 samples of soft drinks from California to New York over an eight-month period. They found two products in California – Pepsi One and Malta Goya, that had more than 29 micrograms of 4-MEI – which require warning labels under California's Proposition 65.
Neither carried such labeling, according to its study. "While we cannot say that this violates California's Prop 65, we believe that these levels are too high, and we have asked the California Attorney General to investigate," said the article on the study in Consumer Reports.
Consumer Reports has also urged the FDA to review its studies of the chemical and to require specific labeling on sodas that contain 4-MEI. On its current website, the FDA says it has "no reason to believe that there is any immediate or short-term danger presented by 4-MEI at the levels expected in food from the use of caramel coloring."
But in a prepared statement the FDA said that it "appreciates the work done by Consumer Reports on the use of caramel coloring in soda" and is reviewing new data on the safety of 4-MEI.
"These efforts will inform the FDA's safety analysis, and will help the agency determine what, if any, regulatory action needs to be taken. Currently, the FDA has no reason to believe that 4-MEI, at the levels expected in food from the use of caramel colors, poses a health risk to consumers."
The FDA's website summary on 4-MEI also reveals that tests done in mice involved levels of exposure that "far exceed current estimates of human exposure" from colas.
"Keep in mind that these levels of carcinogen seem to be found if you take that amount every day for a lifetime," said Keith Ayoob, a nutritional specialist and associate professor of pediatrics at Albert Einstein College of Medicine. "Frankly, people shouldn't worry about one soda. But if you really are drinking more than one soda a day, you are probably drinking too much soda."
"Sometimes I think a better indicator of the quality of the diet is not just the food or the beverage, but what your diet is total," said Ayoob. "People say six sodas a day may harm you -- it might or might not -- but it's what you are displacing when you are drinking that much soda."
Ayoob and others suggest consumers who are concerned switch to colorless soda. "There are plenty of alternatives that don't contain the caramel color," he said. "There is no reason to panic. It's another opportunity to look at your eating habits and look where the excesses might be."
But Urvashi Rangan, the lead scientist on the Consumer Reports study, which was done in partnership with the Johns Hopkins Center for a Livable Future, said the goal of the study was to "increase awareness around the problem and potential carcinogens in the food supply."
Rangan is a vocal opponent of environmental pollution and toxins.
4-MEI "is used commonly in soft drinks, which are something we drink a lot of, but not necessarily a dietary necessity," she told ABCNews.com. "What you know about it and what you do depends on your own level of risk tolerance. When you talk about cancer, what you change today can matter tomorrow. … Even moderating your levels of consumption, if it is big, can mitigate risks."
"It's not about all or nothing," she said. "Less is more when you are talking about exposure to 4-MEI."
PepsiCo said in a prepared statement that it "abides by the law everywhere we do business" and is now meeting California's requirements and voluntarily applying them in the rest of the country.
"We are extremely concerned about Consumer Reports' allegation that one of our products exceeds the Prop 65 standard and requires a warning label," the statement said. "We believe their conclusion is factually incorrect and reflects a serious misunderstanding of Prop 65's requirements."
"Applying the Prop 65 standard of per day exposure and based on the Consumer Report analysis, the highest amount of 4-MEI reported in Pepsi One equates to less than 14 mcg in the amount consumed per day by the average consumer. That is well below the Prop 65 labeling requirement of 29 mcg in 100 ml, and therefore does not require a warning."
Meanwhile, Consumer Reports' scientist Ranjan told ABCNews.com that its data on the concentration amounts of 4-MEI were "correct."
"They are disputing the daily consumption of soft drinks," she said of PepsiCo's position.
She said PepsiCo arrived at their conclusion by including people with low-consumption rates, such as children under the age of 2, in their averages. "We looked at the same data of regular soft drink users who can drink up to two and half servings a day," said Ranjan. "They were all over 20."
Goya Foods said in its statement it was "concerned for the health of our consumers and committed to ensuring the quality and safety of Goya products."
"We are working closely with our suppliers and continue to examine the issue. We do not directly produce Goya Malta nor its ingredients and was unaware of the level of 4-MEI found in our products and the proper labeling required in the state of California based on Prop 65. We rely on our suppliers to provide us with pertinent information and guidelines to make our products safe and of the highest quality."
Rangan said several companies, including Coca Cola, had already reduced the amounts of caramel coloring in their products. "It's an unnecessary risk we can do something about," she said.
Consumer Reports is also asking the Food and Drug Administration to make more specific labeling on products that contain 4-MEI. In Europe the specific types of coloring – 3 and 4 – are spelled out on the labels, according to Rangan.
"We also want the government to not allow a product to be called 'natural' if it contains these artificial colors," she said.
In a prepared statement for ABC News, the American Beverage Association said consumers can "rest assured that our industry's beverages are safe."
"Contrary to the conclusions of Consumer Reports, FDA has noted there is no reason at all for any health concerns, a position supported by regulatory agencies around the world. In fact, FDA has noted that a consumer 'would have to drink more than a thousand cans of soda in a day to match the doses administered in studies that showed links to cancer in rodents.' However, the companies that make caramel coloring for our members' soft drinks are now producing it to contain less 4-MEI, and nationwide use of this new caramel coloring is underway."