The Food and Drug Administration has raised questions about three out of four studies that General Mills used to support health claims for the nation's top-selling breakfast cereal, Cheerios.

The oat cereal is one of the biggest earners at General Mills, which argued this summer that it should be allowed to say that a diet of Cheerios cuts levels of low-density lipoprotein (sometimes referred to as "bad") cholesterol by specific amounts.

The FDA's letter, sent Oct. 9 and made public after a Freedom of Information Act request by the Star Tribune, said studies submitted to the FDA for two claims -- which appeared on boxes as "4% in 6 weeks" and "10% in one month"-- were either too short or incomplete.

General Mills dropped both claims from its boxes of Cheerios, according to a spokesman, but it continues to press the matter with the FDA.

Cereal king

The back-and-forth involves the sometimes-arcane rules of food labeling, which nevertheless can affect millions of dollars in sales.

Cheerios has long been the breakfast cereal king -- about 1 out of every 8 boxes of cereal sold at supermarkets, according to data from the Nielsen company. It claims more than twice the market share of the runner-up, Kellogg's Special K.

But Cheerios has been under regulatory fire ever since the FDA said this summer that labeling on its boxes overstepped the rules for health claims.

Under current labeling laws, Cheerios may make the claim that it can lower the risk of coronary heart disease when eaten as part of a diet low in saturated fat and cholesterol. The law allows food manufacturers to make a second claim that specifically mentions a certain food -- for Cheerios it's oats or "whole-grain foods" -- as long as it's made as part of the more general claim about soluble fiber.

The FDA sent a warning letter to General Mills in May that talked about serious violations of the Food, Drug and Cosmetic Act, drawing attention to the Cheerios claim that it can "lower your cholesterol 4 percent in six weeks." Even the placement of that statement on Cheerios boxes was problematic, the agency said, since the claim appeared in large print on the front of the box. A smaller, second statement that appeared near the edge of the box said the cholesterol reduction also required a diet low in cholesterol.

Shortly after the FDA issued its warning letter, General Mills responded by citing four peer-reviewed studies conducted in the past 11 years.

Body of research

Barbara Schneeman, director of the office of nutrition, labeling and dietary supplements in the FDA's Center for Food Safety and Applied Nutrition, said in her Oct. 9 letter to General Mills that just one of the studies, Johnston et al. (1998), stood up to her office's review. The study supports the claim that 3 grams per day of soluble fiber (meaning three servings or 3 cups of Cheerios per day) would cut bad cholesterol by 4 percent in six weeks, Schneeman wrote.

Yet health claims must take into account not just one study, but every relevant study, according to FDA rules, and the three other studies that General Mills submitted don't seem to clearly support the claim, Schneeman wrote, referring to Karmally (2005), Reynolds (2000) and Maki (2009).

Comparison was lacking

Two of the studies don't report the average cholesterol reduction for people in the study who ate Cheerios vs. people who didn't eat Cheerios. The third study lasted four weeks, not the six weeks suggested in the Cheerios claim.

The FDA's letter also said that both the "4 percent in 6 weeks" claim and the "10 percent in one month" claim are based on three servings (3 cups) of Cheerios daily. The letter went on to suggest that the phrases might need to be reworked to make it clear that they don't refer to a single serving.

The company responded Nov. 3 in a letter -- since posted to its website -- that points to information in the studies that it says supports its claims. "We're standing behind our science," said company spokesman Tom Forsythe.

The FDA has yet to respond.

Matt McKinney • 612-673-7329