Beans are very nearly the perfect food: Packed with vitamins, minerals, protein and fiber, they’re also quite low in fat. They are known as “nutrient-dense” foods, meaning they provide a lot of nutrition per calorie. On top of that, they’re cheap.

“They’re truly the unsung heroes of our food chain,” says David Grotto, a registered dietitian and author of “101 Optimal Life Foods” and “101 Foods That Could Save Your Life!” So it’s no wonder beans are favored in the 2010 Dietary Guidelines for Americans. That document, which spells out the federal government’s recommendations for healthful eating, includes beans on a short list of foods we should all be eating more of.

How much?

The new guidelines recommend eating 1 1/2 cups of beans a week. That’s half of what was suggested in the 2005 guidelines but still way more than one-third of a cup, which is Americans’ median weekly intake of dried beans and peas, according to Trish Britten, a nutritionist with the USDA’s Center for Nutrition Policy and Promotion. That figure wasn’t available when the 2005 guidelines were written; the new guidelines reflect a more achievable goal.

The basics

What’s a bean? Legumes are plants whose seed pods split into two halves. Beans and peas are the mature, edible seeds of some such plants, according to the guidelines. Examples such as kidney beans, pinto beans, black beans, garbanzo beans (or chickpeas), lima beans, black-eyed peas, split peas and lentils all fall under the category of beans, according to the guidelines.

What’s not a bean. Green beans, which are listed in the guidelines as a green vegetable, and green peas, listed as starchy vegetables. Neither is a legume. Soybeans and peanuts are legumes but not considered beans under the guidelines.

Beans and legumes (iStock Photo)

Vegetable and protein. Beans and peas are staples of these two food groups in the Dietary Guidelines. If you get plenty of protein, feel free to include beans in your vegetable tally (2 1/2 cups a day is recommended). For vegetarians and vegans, beans can be a key source of plant-based protein.

The benefits

- Fiber. Because they are so packed with fiber (a half cup delivers six grams, about a quarter of your daily need), beans make us feel full quickly and help maintain that feeling for a long time. Fiber consumption has been linked to reduced risk of cardiovascular disease, being overweight and Type 2 diabetes.

- Vitamins, minerals and more. Beans are rich sources of iron, zinc and folate, and they’re high on the list of foods containing antioxidants, which are thought to protect against inflammation and cell damage by combating stray oxygen molecules (“free radicals”) that harm our bodies’ tissues. In general, the deeper the color of their skin, the more antioxidants they offer. Plus, beans, like other vegetables, contain lots of potassium, which may help protect against high blood pressure and stroke.

- Value. When it comes to cheap eats, you can hardly beat beans. At my grocery store, for instance, a 16-ounce bag of dried garbanzos is $1.69 and yields 10 quarter-cup cooked servings (about 17 cents a serving). A 16-ounce bag of dried lentils is $1.49 and makes 14 quarter-cup servings (about 10 cents each). Even canned beans are a bargain: A 15-ounce can of black beans costs $1.29 and contains six quarter-cups (about 20 cents apiece). And a 16-ounce can of red kidney beans, also $1.29, has seven quarter-cup servings (about 18 cents each).

Consumer concerns

Sodium. Canned beans, though more convenient than dried, are swimming in sodium. Some manufacturers offer reduced-sodium versions. Draining and rinsing them in a colander cuts sodium by 40 percent, Grotto says.

Cooking. Dried beans require the extra steps of soaking and cooking. To save labor, cook a bunch at once and freeze what you don’t use.

Refried beans. These are perfectly good beans, Grotto says. They’re just cooked pinto beans that have been mashed up. Sometimes they’re cooked with lard or vegetable oil; look instead for fat-free varieties such as those offered by Ortega and Old El Paso.

The musical fruit? If beans make you toot, blame the carbohydrate raffinose, which hangs around in our digestive tracts when we eat beans (as well as cabbage, broccoli and some whole grains), Grotto says. Our bodies lack the enzyme needed to digest raffinose, which ends up fermenting in our guts. The problem’s worse when we suddenly introduce fiber to our systems, he says. To avoid getting gassy, try phasing in beans, starting with just a tablespoon a day, Grotto suggests. If that doesn’t work, try Beano or similar supplements, which contain a key bean-digesting enzyme.

Recipes on the Web

Beans are versatile and work well with all kinds of other ingredients. Find these recipes in the Food section’s Recipe Finder at washingtonpost.com/recipes.

- Black Bean and White Bean Primavera Salad

- Chicken Chili

- Chicken Tacos with Black Beans and Lime Cream

- Stuffed Peppers with Ancho Sauce

- Pan-Roasted Scallops with Mandarins and Chickpeas

By the numbers

1 1 / 2 : The number of cups per week a person on a 2,000-calorie daily diet should eat. That’s just under a quarter cup a day. You can do that, right?

4: Cups of cooked beans and peas recommended each week for a vegetarian who eats eggs and dairy.

Previously in this series: Find guides to eating more whole grains and fish.

Nutrition news: Visit the Checkup blog , follow @jhuget on Twitter and subscribe to the Lean & Fit newsletter.

This column is part of a series about incorporating the Dietary Guidelines for Americans 2010 into your diet.