There is one widespread myth in the world of food and nutrition that urgently needs to be debunked: People think that it's more expensive to eat a nutritious diet.

When my clients switch to healthier diets, they tell me their food costs plummet. When I was a poor college student and later a young professional starting out, having little money to spend on food kept me healthier than ever.

Could my experiences be so off base?

Some argue that eating healthy is costly in several respects.

First, they say that 1,500 calories of McDonald's burgers and fries is cheaper than 1,500 calories of healthy food. While this might be true in some cases, this argument is all about quantity and not about the quality of the calories consumed. It also fails to recognize the astronomical health costs of being overweight or unhealthy as a result of regular (though cheap) fast-food dining.

Second, they contend that eating frugally, which requires shopping and cooking, is time-consuming. But this overemphasizes the time required to prepare a good meal and fails to account for the positive benefits of food preparation. Anyone who has enjoyed the smells, sights and sounds of a farmers market, cooked a healthy meal with family and children helping out or felt the warmth of sharing a homemade meal would dispute that these activities have no value.

Third, some argue that inexpensive food doesn't taste as good. Is there anything more delicious than a summer watermelon in season? A crisp apple in autumn? A savory pot roast or a piping-hot bowl of homemade chicken soup? These are some of the simplest, most healthy and inexpensive items you can eat, according to the U.S. Department of Agriculture's Economic Research Service (ERS).

Let's take a look at fresh fruits and vegetables. I think we can all agree -- and scientific evidence confirms -- that a healthy diet can be largely defined as one that contains at least five to nine daily servings of fruits and vegetables. But the price of fresh produce is often cited as too e

xorbitant and one reason Americans fall alarmingly short of the recommendation.

The reality is that fresh produce gives you some of the best bang for your buck. In fact, "consumers can meet the recommendations of three servings of fruits and four servings of vegetables daily for 64 cents," according to a study published in July by the ERS. The study found the average price of fresh fruit was only 18 cents per serving. Canned and frozen fruit cost 24 cents and 51 cents per serving, on average. Fresh vegetables averaged only 12 cents per serving,with canned and frozen costing 17 cents and 22 cents. The study analyzed the 1999 national average retail price of 154 fresh, frozen and canned fruits and vegetables. (Prices have gone up about 10 percent since then, according to the consumer price index.)

Why the disconnect between perception and reality?

"Our advice to consumers is they need to be savvy. Don't just consider the cost per pound, but think about the number of servings you're getting," says Jane Reed, an agricultural economist with ERS and co-author of the study. "People may balk at paying 97 cents for a pound of peaches but they don't realize they're getting four fruit servings." (One serving size is about four ounces or one-half cup for fruits and cooked vegetables, or one cup for raw vegetables.)

When you're buying fruits and vegetables, keep in mind their seasonality and the number of servings they provide. Canned vegetables, for instance, contain liquid -- which is included in the total weight but thrown out, not eaten. Many people find the convenience and shelf life of frozen produce outweighs the small price difference. Throwing out rotted fresh produce, of course, has no benefit, which is why planning your weekly meals is always an important money saver.

Once you find that shopping and preparing food at home are cheaper, you may also reap another bonus: People who lose weight and keep it off prepare most of their meals at home.

In a 2002 study published in the Journal of the American Dietetic Association, 24 families that each included an obese 8- to 12-year-old child followed diets with fewer high-calorie foods and more lean protein sources, fruits and vegetables. After 12 months, the children and parents lost a significant amount of weight, and the total cost of their diet significantly decreased.

These families were reducing the amount of less healthy, calorie-laden foods. It was this change that had the greatest impact on the cost of the diet, according to the authors.

Food with high fat and sugar- and calorie-laden convenience items such as bakery goods, snacks, fried foods and sodas can be very expensive. A 10-ounce bag of potato chips is $2.59 (10 servings of a high-fat, high-calorie, nutrient-poor food), which may seem like a cheap way to fill up. But you could buy four pounds (16 servings) of fiber and vitamin C-rich fresh red potatoes, or three pounds (12 servings) of vitamin-, mineral- and beta-carotene-rich carrots -- for the same price!

Also, when switching to a healthier diet, many people cut down on the portion size of expensive, fatty meat cuts. Switching to smaller servings of leaner meats, poultry and vegetarian protein sources not only saves your health but saves money, too.

Planning and organization are important for saving money. Take an inventory of what you have on hand and shop from a list based on your needs and weekly menu plan. And make good use of leftovers.

My clients call me the leftover queen. When I was in college, I built my meals around beans, an inexpensive but excellent protein source. I ate plenty of vegetables fruits and skim milk. (It's all I could afford!) Some of my favorites were veggie chili, split pea soup with ham, chicken corn soup, carrot yogurt soup, lasagna, Asian chicken or tofu stir-fries, and spicy bean- and grain-based salads. I made them in huge pots on my boyfriend's two electric burners or in my tiny group house kitchen. I couldn't afford to eat out, so I had no temptations there.

Funny, I still batch cook and usually build meals around beans and other plant foods. It's not only inexpensive; it's healthy, delicious and it saves time. My clients agree.

Katherine Tallmadge is a Washington nutritionist and author of "Diet Simple" (Lifeline Press, 2004). Send e-mails to her at food@washpost.com.