We hate to break it to you, but it looks like soda isn't good for you after all.

The Food and Drug Administration (FDA) is warning the Coca-Cola Company to revise its labeling of Diet Coke Plus so that it doesn't mislead consumers into believing that the pop, a brew of chemicals mixed in with some vitamins and minerals, is healthy.

A letter posted on the FDA's Web site yesterday tells Coke that the soda is "misbranded" because only products that contain at least 10 percent more of the Reference Daily Intake (RDI) or Daily Reference Value (DRV) for a given nutrient "than an appropriate reference food" can legally call themselves "plus." The Diet Coke Plus label doesn't name such a reference food, says the FDA. RDI refers to how much daily consumption of a particular nutrient is sufficient for healthy adults, and it's included in the DRVs on nutrition labels that base those values on caloric intake.
In the letter, dated Dec. 10, the FDA gave Coke 15 days to tell the agency how it plans to fix the violation of the Federal Food, Drug, and Cosmetic Act, which spells out the criteria according to which a company can make nutritional and health claims.

A spokesperson for the company, Scott Williamson, said in a statement that Coke would respond to the FDA early next month. "We take seriously the issues raised by the FDA in its letter," Williamson said. "This does not involve any health or safety issues, and we believe the label on Diet Coke Plus complies with FDA's policies and regulations."

The product's Web site claims that Diet Coke Plus, introduced last year, "provides 15 percent of your RDI for niacin (a B-vitamin) and vitamins B6 and B12, and 10 percent for zinc and magnesium."

The agency's warning letter is a notable commentary on the booming enhanced beverage industry. Many drinks — from water to coffee — are now dosed with vitamins and minerals, but the FDA doesn’t closely scrutinize their health claims, the Wall Street Journal notes.

In its letter, though, the FDA said it "does not consider it appropriate to fortify snack foods such as carbonated beverages."

So much for the "fortification" we were going to add to our soda water this afternoon.

Updated at 4:10 p.m. to clarify criteria for food products labeled "plus."

Image of Diet Coke Plus/The Coca-Cola Company