Buffeted by changing consumer demands and concerns over the health effects of excess salt and sugar, the world's largest food companies have tried to make their products more healthful.
Many have promised to reduce sodium and added sugars. Others have removed artificial colors and additives.
But a new, peer-reviewed government report suggests these tweaks have not made packaged foods more healthful overall: While sodium and sugar have decreased in many products, there's been a surge in the amount of saturated fats, which raise blood cholesterol.
Experts say the contradictory trends speak to the immense difficulty of reformulating packaged foods – even at the world's most advanced food companies. General Mills, Kraft, Nestle and many others have struggled to make foods more healthful while also maintaining price and taste.
"Historically, we've tended to focus on one element of the equation at a time: salt or sugar or fat," said Michael Moss, an investigative journalist and expert on the processed-food industry. "They could respond to one of those things pretty easily. But all three is quite difficult."
The new report, published by the Agriculture Department in November, shows that companies have made uneven progress on their nutrition goals. In the case of some products, the authors write, it is "not clear" whether foods touting new health claims "are healthier overall."
To reach that conclusion, USDA economists examined the nutritional content of thousands of new and revamped food products that entered the marketplace between 2008 and 2012 and compared them with existing products. They focused on breakfast cereals, yogurts, snacks, candies and frozen and refrigerated meals, which make up the bulk of sales of packaged foods.
When it came to salt, sugar and fat, the trends were clear. Sugar content has either fallen or remained the same across all five food categories. Sodium content has fallen in all five categories except one – frozen meals – where it's up slightly.
But saturated fat, which the American Heart Association calls a contributor to cardiovascular disease, has increased a statistically significant amount in cereals, yogurts, snacks and frozen meals. Candy, the one category where the researchers did not observe an increase, does not contain fat in significant quantities.
"These contradictory trends support the contention that policies focusing on reducing a single nutrient, such as sodium, may not lead to overall healthier products," the researchers conclude.
That doesn't surprise food industry insiders, who say that sugar, fat and salt are critical components of most packaged foods. Reducing the sodium and sugar in a product almost inevitably leads to a higher fat content, said Ryan Dolan, chief operating officer of PTM Food Consulting. The company helps food manufacturers – including Kraft Heinz, ConAgra, and Kellogg's – develop healthier versions of their products.
Dolan likens a product's nutrition to a pie chart, with slices for nutrients such as sugar, fat, protein and other carbohydrates. If a food company makes one slice smaller, and keeps the product weight the same, the other slices necessarily have to expand.
"So any time you focus on decreasing one nutrient, you increase the others," Dolan said.
This is frequently true even if a replacement ingredient – say, stevia for sugar – is added to the "pie" during reformulation. Food scientists use these more potent ingredients in smaller quantities, so they don't compensate entirely for the weight and volume of the nutrient they've replaced.
It's a phenomenon researchers have observed in the past, said Marlene Schwartz, the director of the University of Connecticut's Rudd Center for Food Policy and Obesity. In her work on children's cereals, Schwartz has urged food companies to reduce the amount of added sugars.
"Someone from the company basically pointed out the logic – if you have 100 grams of a food, and you take out some of the grams of sugar, you have to put something else in," she said. "And, yes, since fat, sugar and sodium are key components of palatability, there is going to be some juggling of those three ingredients."
It's far from certain that sodium and sugar reductions contributed to increased saturated fat levels in this specific case. David Levin, the co-author of the USDA report, acknowledged that it's a possibility – but said that mathematical modeling, which he did not conduct, would be needed to validate the connection.
In the meantime, there are other explanations for these trends, said Barry Popkin, a professor of nutrition and economics at the University of North Carolina at Chapel Hill.
Sodium reduction initiatives from industry and government have led companies to slash salt, he said, and a consumer revolt against sweetened foods and beverages has encouraged sugar cuts. As for saturated fats, he said, there is some evidence to suggest that manufacturers have used them to replace their more dangerous cousin, trans fats.
F orthcoming research from his team has also found that some foods that typically contain more saturated fats, such as savory snacks, have become more popular with consumers. The report notes that whole-milk yogurt, for instance – which contains more saturated fat – has seen a resurgence.
"They are independent trends," he said – although he expects them to interact in the real world.
"The increase in saturated fats may offset some of the gains we've made with sodium reduction, in terms of things like heart disease," Popkin added.
Whatever the cause, experts agree the report's findings show how difficult it can be to improve packaged foods. That's why Dolan and Pete Maletto, PTM's president, encourage companies to consider the entire product during reformulations, rather than specific ingredients, such as sugar.
The best way to develop a nutritious product, they argue, is to focus on using fewer ingredients and moderate amounts of salt, sugar and fat.