BOSTON, JAN. 23 -- Science has a word of advice for anxious parents of picky eaters: Relax.

A new study concludes that grownups need not -- and probably should not -- force children to clean their plates. Left to their own devices, youngsters will almost certainly get enough to eat.

"It's the parents' job to supply kids with an array of nutritional foods but the child's job to decide when and how much to eat," said Leann L. Birch, a psychologist at the University of Illinois at Urbana-Champaign. "Parents should not try to stuff food into their child."

Birch's study, published in Thursday's issue of the New England Journal of Medicine, confirmed what every parent knows: Children are finicky at the table. They may find the tuna casserole yummy today but icky tomorrow. One night they wolf down dinner and the next they turn up their noses at everything but apple juice.

Aggravating, perhaps, but not necessarily bad.

"We substantiated parents' observation that children's eating behavior meal to meal is erratic and unpredictable," Birch said. "But that's probably normal. Energy intake over the total day is relatively tightly regulated."

In other words, children tend to take in almost the same total amount of calories each day, even though consumption and tastes fluctuate wildly from meal to meal. If a 3-year-old declines to eat anything but three grapes for lunch, chances are good that she cleaned up her cereal at breakfast and will put away a decent dinner.

"Parents, particularly fathers, should not be too upset if the kid doesn't seem to be eating," commented Johanna Dwyer, a nutritionist at New England Medical Center. "This shows that there is a fair amount of variability within children from meal to meal, but over the long term they do pretty well," she said.

Of course, this doesn't mean that children should be allowed to eat just potato chips and grape jelly, even though they might want to. Parents should offer healthy fare, both for meals and snacks, and avoid high-fat, nutrient-poor junk food.

Birch based her findings on careful observation of the eating habits of 15 preschoolers, aged 2 to 5, over six days.

Her research helps clear up questions that have lingered since Clara Davis, a Chicago pediatrician, discovered 60 years ago that children survived just fine with no dining instructions from their elders.

In an editorial accompanying the new study, Gilbert B. Forbes of the University of Rochester agreed that the work shows youngsters' "innate ability" to control how much they eat.

"Even with all the food available to them, her young subjects did not eat to excess," he noted. "In this they were wiser than many adults, for whom a plethora of food is but a passport to obesity."