Fruits and vegetables: By now, in these nutrition-conscious days, everyone from the man in the street to the smallest kindergarten child knows they're good for you. A lot of us also know why. Many vegetables are rich in vitamins such as beta carotene (which the body converts to vitamin A) or vitamin C, and they're low in fat and calories and high in fiber.

If we know all that, why don't we eat more? In recent years, supermarkets have increased space for the produce section, suggesting that consumption has risen. But according to a study reported in the American Journal of Public Health, the increased consumption is unevenly distributed. True, the data were collected at least 10 years ago as part of the second National Health and Nutrition Examination Survey (NHANES II) .But as the authors from the National Cancer Institute point out, comparisons from smaller and more current surveys confirm the sad fact that when it comes to eating our fruits and vegetables, many of us still fall woefully short.

What the researchers did was to look at a day in the life of 12,000 adults who participated in the NHANES II survey, which was carefully designed to provide a representative picture of the entire U.S. population. In making the tallies, a serving of fruit was defined as an average piece of whole fruit or six ounces of juice. Fortified and non-fortified fruit "drinks" weren't included. A serving of vegetables was generally considered to be half-a-cup.

Using such measures, researchers compared consumption patterns to recommended guidelines for a healthy diet. This included three or more servings of vegetables a day and two of fruit. The result? In the words of the authors, the proportion of individuals meeting these guidelines was "shocking." Only 29 percent of study participants consumed the suggested amount of fruit. Vegetables fared even worse: a mere 27 percent met the quota, particularly distressing considering that both potatoes and dried beans were included in this group.

Adding insult to injury, only 9 percent met both targets! Forty-five percent ate no fruit, 22 percent had no vegetables, and 11 percent ate neither fruit nor vegetables on the day the information was gathered. It was a day of infamy from a nutritional point of view.

Those who ate neither fruit nor vegetables consumed less than 6 grams of fiber, or about one-fourth of the National Cancer Institute's recommendation of 20 to 30 grams per day. In sharp contrast, the subjects whose diets met the combined five-serving target for fruits and vegetables consumed an average of 17 grams of fiber. Only those eating three servings of each, a tiny 4 percent of adults, achieved the 20 to 30 gram goal.

Beta carotene from fruits and vegetables is estimated to provide half the total vitamin A pool in the American diet. Here the picture was somewhat better. On average, people eating two servings of fruits and vegetables were likely to be getting the entire U.S. Recommended Daily Allowance (US RDA) of 5,000 International Units. That leaves 11 percent off the mark. On the other hand, of the more than 50 percent of the population who ate only fruits or vegetables, not both, it took three servings to reach an average of 5,000 IU of vitamin A.

As for vitamin C, fruits, of course, make the difference. Without fruit (and remember that 45 percent of the population consumed none on the day in question), only those who ate an average of three servings of vegetables a day met the US RDA target for vitamin C of 60 milligrams.

If the man on the street can tell you that fruits and vegetables are nutritional gold mines, why are these data so out of sync? If we know what to do, why don't we do it? Part of the explanation might be that many fruits and vegetables are expensive, simply beyond the reach of some families. Yet some can be an excellent buy - fresh, frozen or even, in certain cases, canned.

If a tight budget is your excuse for not getting enough fruits and vegetables, it's time to explore the supermarket more carefully to come up with some economical choices. It's better to skimp in other areas than to rule out nutrient-rich produce.

And if the problem is not with your wallet, then you really have no excuse. We're not trying to sound like a scolding teacher, but if you're passing up fruits and vegetables for no valid reason, you're depriving yourself of sound nutrition as well as good taste.