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In Washington, a pivotal battle over sugar is heating up. One small corner of the wider culture war over public health and sweeteners, this fight isn't about how much sugar should be in your food, but how much you should know about it.

U.S. food regulators say the public needs to know how much sugar manufacturers add to their products, beyond the sweetener that naturally occurs in the raw ingredients. Companies such as Campbell Soup Company say they don't need to inform the public, and that making a distinction risks dangerous confusion.

This week the Food and Drug Administration will begin reviewing thousands of public comments on proposed new labeling regulations that would require food makers to specify how much sugar they are adding to products. Current labeling laws only require them to list total sugar content.

The move marks U.S. regulators' first significant step to address a growing clamor from health groups and scientists who say that excessive sugar consumption is a key culprit in the nation's obesity and diabetes epidemics.

It also comes amid growing public demands for greater transparency in the U.S. food supply chain, fueled by interest in everything from animal welfare to genetically modified grain.

"There's been an increasing drum beat on the part of public health advocates to give consumers that information," says Michael Jacobson, the head of nonprofit food advocacy group Center for Science in the Public Interest, which has spent decades crusading to tackle high sugar levels.

Jacobson said he was "delighted and almost in disbelief" when he heard of the FDA's plans, which were announced in February.

Not everyone is thrilled. If added, the line would be a major blow for sweetener companies already battling each other in an overcrowded industry as the growth of America's massive sweet tooth stalls.

It is impossible to determine how many sugars have been added to a container of yogurt, unless companies choose to disclose it. Sugar is used to enhanced flavor in a wide range of products, beyond simply cookies and sodas.

The fight is about to get serious, with lobbyists on either side expected to step up pressure as the FDA reviews public comments ahead of issuing a final rule. From there, it would likely be years before companies are required to update their labels.

'SUGAR IS SUGAR'

U.S. government data shows that per capita consumption of caloric sweeteners has been declining for over a decade, but health groups say it is well above healthy levels.

Some nutrition experts and scientists say sugars that are added to foods are greater contributors to weight gain, adding calories without the benefit of other nutrients. A few even say sugar itself is toxic.

That stance remains a controversial one. Food manufacturers and sugar companies resoundingly say there is not enough evidence to suggest "added sugars" contribute differently to weight gain than sugars that are intrinsic to a piece of fruit.

"Sugar is sugar, regardless of the source," Campbell Soup Company, the maker of Pepperidge Farm and Prego products, wrote in a letter to the FDA.

"Giving consumers a false impression that reducing added sugars without reducing calories may actually delay finding a real solution the problem" of obesity, Lisa J. Thorsten, the company's director of regulatory affairs and nutrition, wrote.

The Sugar Association, which represents the makers of household brands, including Domino Sugar and Imperial Sugar, went further, saying the lack of scientific evidence to justify the line sets an "alarming precedent."

But CSPI's Jacobson and a number of other health advocates insist that added sugar are different and are hidden sources of empty calories at the very least.

The American Heart Association recommends that women, for example, consume no more than about 6 teaspoons of added sugars each day. That is less than the amount in a 12-ounce can of Coca-Cola.

The World Health Organization in March issued a draft of new guidelines advocating people cut the recommended amount of added sugars they eat in half, updating the guidelines it introduced a decade ago.

"The big difference between now and then (is) we have a system to provide the guidelines," said Francesco Branca, the WHO's nutrition department director. "We have credibility from the scientific point of view that make these guidelines easier to defend."

FOR 'JUNK FOOD' CRITIC, A LONG TIME COMING

Some critics doubt the effectiveness of the so-called "facts panel" overhaul. The U.S. government earlier this year said that just around half of all consumers read the labels and make decisions based on the information.

"The people who read labels are the people who are already watching their health and their weight. This isn't going to cause a dramatic change," said Baylen Linnekin, head of nonprofit Keep Food Legal and a critic of the labeling measure as well as other government involvement in the food sector, including subsidies.

The Sugar Association also said the move represents a concerning extension of regulatory power in requiring food makers to turn over private records to the U.S. government.

The regulators' move underscores the growing public scrutiny of sugar consumption, a trend that cheers Jacobson, who has targeted soda makers and sued food companies in a self-appointed role as the nation's "food cop."

Washington-based public relations specialist and industry advocate Rick Berman says Jacobson is in the "food hysteria business" and dismisses the anti-sugar craze as a fad.

With industry lobbying efforts building up, Jacobson, 71, said he is "not planting the white flag yet." But he is quietly savoring what could be the most meaningful step in his quest.

"It has been a long, long time."