Are you worried about high-fructose corn syrup in your diet?

If you answered yes, you're not alone. Today, about 55 percent of Americans list the infamous corn sweetener among their food-safety worries, right behind mad cow disease and mercury in seafood, according to the consumer research firm NPD Group.

As a result, food makers are reworking decades-old recipes, eliminating the corn syrup used to sweeten foods like ketchup and crackers, and replacing it with beet or cane sugar. To counter the backlash, the Corn Refiners Association last week suggested changing the name of the ingredient to ''corn sugar,'' hoping a new moniker would help rebuild the product's image.

But most nutrition scientists say that consumer anxiety about the sweetener is misdirected. Only about half of the added sugar in the American diet comes from corn sources. All added sugars, they say, including those from sugar cane and beets, are cause for concern. Today, sugar calories now account for 16 percent of the calories Americans consume, a 50 percent increase from the 1970s. High sugar consumption has been linked to obesity and other health concerns.

''I think consumers have been misled into thinking that high-fructose corn syrup is particularly harmful,'' said Michael Jacobson, executive director of the Center for Science in the Public Interest, an advocacy group. ''Chemically it's essentially the same as sugar. The bottom line is we should be consuming a lot less of both sugar and high-fructose corn syrup.''

High-fructose corn syrup and sucrose, also known as table sugar, are made up of about the same amount of glucose and fructose. The American Dietetic Association says the two sweeteners are ''nutritionally equivalent'' and ''indistinguishable'' once absorbed in the bloodstream. The American Medical Association has said it's ''unlikely that HFCS contributes more to obesity or other conditions than sucrose.''

But there are some differences. To make table sugar, the sugar from beets and cane essentially is squeezed out of the plants. Corn syrup, meanwhile, is heavily processed using enzymes to turn cornstarch into glucose and then fructose.

In high-fructose corn syrup, the glucose and fructose molecules are chemically separate. In table sugar, the molecules are chemically bonded, forming a disaccharide that is broken apart inside the body.

Much of the confusion about high-fructose corn syrup stems from a 2004 article in the American Journal of Clinical Nutrition that suggested rising obesity rates were related to increased consumption of high-fructose corn syrup in beverages. The lead author, Dr. George A. Bray, said in an interview last week that the real issue highlighted in the report was overconsumption of all sugary beverages, but that the article has been distorted as an indictment of high-fructose corn syrup alone. Dr. Bray notes that the fructose absorbed from large quantities of regular sugar and from high-fructose corn syrup is equally harmful. ''Sugar is sugar,'' said Dr. Bray, professor of medicine at the Pennington Biomedical Research Center in Baton Rouge, La.

But some researchers continue to put forth the theory that high-fructose corn syrup has a more nefarious effect on health than regular sugar. This year, psychology researchers at Princeton University published a report on a series of experiments that tracked weight gain among male and female rats that were given regular rat chow, along with 12- or 24-hour access to water sweetened with either sucrose or high-fructose corn syrup. In some of the comparisons, there were no significant differences in weight gain between the groups. Among rats with 12-hour access to high-fructose corn syrup, the males gained more weight but the females did not. Among rats with 24-hour access to high-fructose corn syrup, the females gained more weight but the males did not.

The Princeton researchers say the experiments suggest that high-fructose corn syrup prompts more weight gain than sucrose, at least in rats, even when the animals eat the same number of calories over all. They speculate that the body metabolizes the calories in high-fructose corn syrup differently than the same amount of calories in regular sugar, prompting the body to pad on extra pounds.

''We know from our measurements that after a few months, the high-fructose corn syrup drinkers weighed more,'' said Bart Hoebel, a psychology professor and a senior author on the research. ''That's what makes this interesting and surprising.''

But critics of the Princeton study say the findings are inconsistent - some of the rat groups, after all, showed no differences in weight gain.

''How they came to these conclusions is beyond me,'' said Marion Nestle, a professor in New York University's department of nutrition and a longtime food industry critic who wrote about the research on her Food Politics blog. ''I'm skeptical. I don't think the study produces convincing evidence of a difference between the effects of HFCS and sucrose on the body weight of rats.''

Dr. Bray said differences in the taste preferences of rats and in their metabolism make it tricky to evaluate food intake, calories burned and weight changes. ''It's not easy to measure,'' Dr. Bray said.

Dr. Bray said that while high-fructose corn syrup isn't any more detrimental than regular sugar, the benefit of focusing on the ingredient is that it has drawn attention to too much sugar in the American diet.

''It allowed us to see a rapid rise in its use and opened up the discussion about rising fructose intake,'' Dr. Bray said. ''Sugar is one of the commodities of which we've never had a surplus. We've always consumed all that's ever been produced.''
