WASHINGTON (Reuters) - americans were told tuesday not just to eat up their fruits and vegetables, but to make them the cornerstone of their diets.

A coalition of more than 20 groups, including the american heart Association, the american cancer society and the american association of retired persons (AARP) urged the government to make fruits and vegetables the center of the ideal american diet in upcoming new nutritional guidelines.

The dietary guidelines Committee, which includes officials from the U.S. department of Agriculture, the department of health and human services and top nutritionists from various universities, releases new dietary guidelines next year.

The foundation and the other organizations want the guidelines revised, to make fruits and vegetables the core of the recommended diet.

The current "food pyramid," used as the basis for school lunch programs, by nutritionists and by most nutrition education programs, has at its base grains, with fruits and vegetables next, then dairy and meat, nuts, beans and legumes, and tops off the pyramid with fats and sweets.

The groups want this concept revised, with americans told to center their diets on fruits and vegetables.

Current guidelines also advise people to eat five servings a day of fruit and vegetables. but americans still do not eat enough, the groups said.

Colin Campbell, a professor of nutritional sciences at cornell university in new York, said people can get all the nutrients they need from fruits and vegetables.

"There are no essential nutrients in animal-based foods that are not also available, to better advantage, in properly grown plant-based foods," he told a symposium on the petition.

All the groups say there is strong evidence that if people eat more fruits and vegetables, lives and a considerable amount of health care dollars will be saved.

"The evidence is very strong that those who eat five or more servings of fruits and vegetables daily are at a lower risk of cancer," Dr. david Rosenthal, immediate past president of the american cancer Society, told the conference.

While one-third of all cancers are related to tobacco use, another full third are related to diet, he said.

Rosenthal said it will take more than guidelines to get americans to eat differently, but this will be a first step.

"We showed that we could do it with tobacco," he said. "The same type of cultural change has to take place with eating."

Karen Weber-Cullen, a behavioral scientist at the university of texas M.D. anderson cancer Center, said the right food is often available, but not in a form that most people want to eat. "I doubt that most kids go into a fast-food restaurant and order a salad," she told the news conference. "Why do we need a double cheeseburger? I'd like to see a double tomato burger."