Who knew corn could be so sweet? Who knew corn could be so controversial?

The same food that gives us muffins, grits and tamales now accounts for about half of the added sugars that Americans consume each day.

Most of it — about 60 pounds per person per year — is in the form of high fructose corn syrup, or HFCS. You can't buy it for your pancakes, but HFCS sweetens everything from soft drinks to ketchup, yogurt to bread, bacon to ice cream.

Backers say it's economical, domestically produced and in many ways superior to the cane sugar that it often replaces.

"HFCS actually enhances fruit flavors," says Audrae Erickson, president of the Corn Refiners Association, an industry trade group. "It gives a browning color to breads. Because it doesn't crystallize like sugar, it helps products retain their moisture, which lends a chewy texture to cookies and breakfast bars."

The benefits go on and on, she says, at a lower cost to consumers than sugar and with no nutritional difference: 4 calories per gram.

Some scientists aren't so sanguine.

"This is 5 to 10 percent of the calorie intake of every American," says Dr. Barry Popkin, professor of nutrition at the University of North Carolina in Chapel Hill. "We really should be studying it more."

Popkin and other researchers have published studies noting that the increase in HFCS consumption has mirrored the country's rising tide of obesity and questioning whether fructose's effect on the body may be a factor.

Politicians and pundits are entering the fray. In Florida, Rep. Juan Zapata called HFCS the "crack of sweeteners" and proposed legislation to ban sales of anything containing it in schools.

New York Times columnist Nicholas Kristof recently wrote that Americans need to cut down on sugary drinks and fired this broadside:

"Our government needs to do much more to control potentially deadly substances — plutonium, anthrax and high fructose corn syrup."

Todd Seavey of the American Council on Science and Health shot back with a column headlined "Kristof goes berserk over high fructose corn syrup."

Last month the Center for Science in the Public Interest, a consumer group that crusades against junk food, threatened to sue Cadbury Schweppes for calling 7UP "all natural." The soft drink, which has no fruit juice, is sweetened with HFCS.

"High-fructose corn syrup isn't something you could cook up from a bushel of corn in your kitchen, unless you happen to be equipped with centrifuges, hydroclones, ion-exchange columns and buckets of enzymes," said the center's director, Michael Jacobson.

"It's a very hot topic," says Cynthanne Duryea, a dietitian at the Cooper Clinic in Dallas. "We haven't seen the end of this."

The food industry insists there is no danger. Erickson says her organization is "working very hard to get out the message of what HFCS is. There's a lot of misunderstanding."

Can we clear it all up? Probably not. But let's examine the issue, a kernel at a time.

Our national sweet tooth used to depend on sugar made from cane or beets. That's sucrose, the white grainy stuff in your sugar bowl. In the late 1960s, Japanese scientists figured out how to use enzymes to break down cornstarch into HFCS, which was just as sweet.

That was great news for American farmers, who had another outlet for their corn crop, and for food manufacturers, who saved money by changing to corn sweeteners.

The switch was on, with soft drinks leading the way. Check the labels at the supermarket, and you'll see that HFCS has replaced sugar on a long list of foods.

According to U.S. Department of Agriculture figures, the average American consumed no HFCS in 1966, 10.8 pounds in 1978, 50.3 pounds in 1991 and about 60 pounds a year today. By the mid-1980s, HFCS consumption passed refined sugar.

"It's such a cheap and high-sweetness item that the food industry is figuring out more and more ways to use it," Popkin says. "You'd be surprised how much of what you consume has it."

So what's the problem? As we've devoured more HFCS, we've also gotten fatter. That's merely circumstantial evidence, but here's the argument:

"HFCS is implicated in the obesity epidemic because it made calories cheaper," says Greg Critser, author of Fat Land: How Americans Became the Fattest People in the World" (Mariner Books, $13).

"It made it possible to turn an 8-ounce Coke into a 16-ounce Coke for the same amount of money and then market it, so people drink more calories."

So little bottles of soda became Big Gulps with free refills. Kids and their parents chose high-calorie, no-nutrition soft drinks over healthy milk and juice. Candy and sweet junk food became cheaper and more plentiful — and Americans got fatter every year.

But beyond the math of calorie intake is a scientific argument. Popkin and others have published studies suggesting that, more than other sugars, fructose may increase triglyceride levels in the bloodstream and may not produce the hormones that tell the brain you're full.

Thus, the theory goes, HFCS might not be putting the normal brakes on your appetite.

A study at the University of Cincinnati made news last year by suggesting that HFCS might cause the body to store more fat. But the conclusions were based on the results of feeding fructose-sweetened water to mice.

The corn and beverage industries think all the above is nonsense. Erickson notes that obesity is rising in places that use little or no HFCS, including Europe and Japan.

"We're consuming too many calories and not getting enough exercise," Erickson says. Critics are "trying to link HFCS as a unique contributor to obesity, and research has found the opposite to be true."

A recent study by Dr. James Rippe of Tufts University — funded by the company that makes Pepsi — concluded that the body handles HFCS no differently than table sugar.

He says the term high fructose corn syrup is "a misnomer, as it makes people think there is much more fructose in HFCS than sugar."

Food industry defenders note that much of the research casting doubt on HFCS has been done with pure fructose. Table sugar (sucrose) is half fructose, half glucose. HFCS is usually 55 percent fructose.

But even those five extra percentage points, Critser says, are "an important increment" that needs more study.

Popkin says he's disappointed that more studies aren't being carried out. One reason, he says, is that much of the funding for food research comes from the food industry.

"They don't like to study adverse effects," he says. "If we thought HFCS had huge benefits, if it prevented cancer, then we'd be studying it."

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So what's a sweet-toothed, scale-tipping American to do? Jacobson, who thinks obesity is a national health crisis, says the culprit isn't specifically HFCS.

It's all kinds of added sugars.

"If soda were still sweetened with sucrose, we would have the same problem," he says. "I haven't seen evidence that HFCS poses a greater threat than sucrose."

The first step to cutting down added sugar, he says, is to know how much sugar has been added. The center has asked the government to recommend a daily limit and then put the information on food labels, just as it does for fat and nutrients.

For the average person, Jacobson says, that should be 10 teaspoons of added sugar per day.

Does that sound like a lot?

"That's how much there is in one can of Coke," Jacobson says.

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HOW TO CUT THE SUGAR

Cynthanne Duryea, a dietitian at the Cooper Clinic, says added sugars should be limited to about 10 percent of your daily calories. Here are some of her tips for trimming sugar intake without making major changes:

—Read labels.

Sugar can be disguised. If the ingredient ends in "ose," it's probably a form of sugar. Check portion sizes. Don't buy cereal with more than 8 grams of sugar per serving. Buy treats in individual packages, such as 100-calorie snack packs, for built-in portion control.

—Dilute.

Combine a package of unsweetened instant oatmeal with one that's sweetened. When dining out, share those desserts.

—Substitute.

Drink diet sodas or flavored sparkling water. Instead of drinking a whole glass of lemonade, add a small amount of lemonade to iced tea. Bake with Splenda, or replace Z\v cup of sugar with a mashed banana.

—Budget.

If you really want to indulge, save your sugar allowance for a few days and spend it all at once.