They used to star on Americans' dinner tables and reign over the USDA's food pyramid (search) — but now foods rich in starch or sugar like orange juice, pasta and potatoes are fighting for their image as they face increasing criticism from promoters of low-carb diets.

According to a Harris Interactive survey done last year, an estimated 32 million Americans are on a low-carbohydrate diet; the NPD Group puts the number at 10 million people.

Although the phenomenal success of low-carb diets has been a boon to makers of specialty products and foods naturally low in carbohydrates, it has created a major headache for others, including the bread, potato, pasta and sugar industries.

While sales of low-carb products have jumped by more than 300 percent since 2000, sales of fresh potatoes have declined 10 percent, instant rice seven percent and white bread nearly 3 percent, AC Nielsen recently reported.

"Since the low-carb phenomenon really took off, there has been a 6.5 percent decrease in pounds of pasta sold," said Ed Schrass, Vice President of Customer Marketing at Barilla North America (search).

"I think what’s happened with carbohydrates is just like 10 years ago with fat: We are unfairly targeting one nutrient," said Cynthia Sass, a registered dietician and spokeswoman for the American Dietetic Association (ADA) (search), the nation's largest organization of food and nutrition professionals.

"Instead, we need to look at the big picture," said Sass, who added that the ADA doesn't promote any particular diet, but focuses instead on healthy eating and individualized nutritional needs.

And the sugar-and-starch industry is starting to fight back.

The Florida Department of Citrus (FDOC) (search) developed its "Operation OJ" advertising plan after seeing a 5 percent decrease in juice consumption over the last three years.

In what will soon become the most visible industry promotion since the ascent of low-carb diets, the FDOC is poised to launch a $6 million TV campaign publicizing the healthfulness of orange juice.

"We are targeting moderate dieters, people who are health- and weight-conscious," said Andrew Meadows of the FDOC. "Our message is orange juice isn’t going to make you fat, it’s going to provide you with Vitamin C, potassium, and folate."

In the first spot, called "Blender," a man is shown putting rutabagas, liver, brussels sprouts, okras, bananas and oysters into a blender while explaining that one could get the same nutritional benefits in a single glass of orange juice.

While advertising is one way of educating consumers about orange juice, pasta defenders are trying a different approach. Oldways Preservation Trust, a food think tank based in Boston, organized a pasta conference called "Healthy Pasta Meals," last month in Rome to tout the benefits of Italy’s once-beloved specialty.

Christopher Speed, manager of food and nutrition strategies at Oldways, said, "We are aggressively trying to convince the trendsetters — media, food manufacturers, doctors, and the general community — that there is a more balanced way of eating than the low-carb diet."

Besides presenting research declaring pasta’s healthfulness, the three-day conference also included multi-course lunches featuring Italian pasta dishes. Pasta manufacturers, including Barilla, sponsored the conference.

Oldways contends that pasta is a means for eating a balanced diet, and recommends primarily the Mediterranean diet that includes fruits, vegetables, breads, pasta, potatoes, olive oil, cheese, yogurt and low to moderate amounts of fish, poultry and red meat for optimal health benefits.

The U.S. Potato Board (search) is also sharpening its marketing knives. Through research, the Potato Board learned that consumers had many misconceptions about potatoes — and found that many believed there was no nutritional value to the potato.

"Our business response to low-carb diets was to re-establish our image nutritionally," explained spokeswoman Linda McCashion. In February, the board’s $4.4 million nutritional campaign began with print ads inviting Americans to "get the skinny on America’s favorite vegetable."

The ads feature a nutritional label on a potato emphasizing its vitamin C, potassium and fiber content. The image is also being placed in supermarkets and some in the potato industry are prominently featuring it on their bags.

Whether all of this marketing will help these foods is yet to be determined, but the ADA's Sass believes it can only help. "While there is no one-size-fits-all diet, the more one learns, the better informed one will be at making at balanced nutritional decisions."