Does a healthy diet cost more than a junk-food diet in America?

That depends on whom you ask, how you measure food and, most important, if you know how to cook.

Earlier this year, the U.S. Department of Agriculture released an analysis indicating that fruits, vegetables, grains and low-fat milk tend to be less expensive by weight and serving size than fatty, sugary foods and meat, fish and poultry.

The takeaway message, according to its authors: Healthful foods actually cost less than foods we are supposed to restrict.

This ran counter to many studies that have measured the cost of “good” and “bad” foods by calorie and concluded that nutrient-poor foods generally cost less.

But recently another group of researchers, including Adam Drewnowski, director of nutritional sciences at the University of Washington in Seattle, decided to look at it from another angle: by the cost of foods that deliver key nutrients, especially those associated with lower risk of chronic disease.

In the study, they found that the foods rich in key nutrients did cost more per calorie than their nutrient-poor counterparts.

“By contrast, nutrients associated with higher disease risk were associated with lower diet costs,” wrote Drewnowski and his colleagues in the study. “The cost variable may help somewhat explain why lower-income groups fail to comply with dietary guidelines and have highest rates of diet-related chronic disease.”

USDA researcher Andrea Carlson objects to the way Drewnowski’s group used calories as a standard of measurement. And Drewnowski objects to the way the USDA used weight as a measurement when, he notes, some of the fruits and vegetables included are composed of 90 percent water.

But the two can agree on one thing: Those who know how to cook are at a distinct advantage when it comes to nutrition on the cheap.

“Theoretically, yes, you can eat healthfully on a budget,” Drewnowski says, but you need to know how to cook whole, unprocessed foods, and that “would require a shift in the way many Americans choose to spend their food dollars.”

His diet analyses find that today many low-income food dollars are spent on processed convenience foods, but if they were instead spent on whole foods, they could go much further.

For this to work, people would need “nutrition education, cooking skills, access to healthy foods, some money and time,” Drewnowski stresses.

“Very often I get letters from people who say that it doesn’t cost any more to eat healthy,” he says. “They say rice and beans are very cheap, but not everyone knows how to make them. … And so as a result, people fall into the pattern of buying processed and less healthy foods.”

Noting that more Americans are reliant today on food stamps than ever, the consumer advocates at the Environmental Working Group have teamed up with anti-hunger organization Share Our Strength to produce Good Food on a Tight Budget ( ewg.org/goodfood), an online guide to buying and cooking cheap, nutritious food.

Drewnowski has also been working on something he calls the Nutrient Rich Food index, which judges food based on nutrients and cost to help people get the most nutrients on their plate for their money.

Other answers may lie in data he is analyzing about people who are able to eat nutritious diets on unusually small budgets.