"We were definitely pleased by the size of the differences, particularly for calories and sugar," said Daniel Taber, the study's lead author and a professor at the University of Illinois at Chicago.

The study doesn't show that students are necessarily replacing unhealthy foods with healthier ones, but the California law "was a bold first step" to improving children's diets, said Patricia Crawford, a professor at the University of California, Berkeley, who was not involved in the study.

Several years ago, California mandated that schools offer so-called competitive food -- that is, food sold in vending machines or other sources outside of the school lunch service -- that meets calorie, fat and sugar limits.

Each snack has to have fewer than 250 calories, no more than 35 percent of calories from fat and no more than 35 percent of its weight from added sugars.

To determine what impact California's regulations have had on students' diets, Taber and his colleagues compared how much children in California ate each day to kids who lived in 14 states that did not have such limits on the foods sold in school.

The study -- published in the Archives of Pediatrics and Adolescent Medicine -- used survey information, collected in the first half of 2010, from more than 100 kids who lived in California and about 560 kids who lived in other states.

The researchers found that the California kids ate 158 fewer calories each day than the other kids, primarily because they ate fewer calories during school hours.

Although the study did not look at whether kids' diets had an impact on their health, "a difference of 158 calories can go a long way toward preventing excess weight gain, particularly if students maintain a healthy level of physical activity," according to Taber.

The California children also ate 17 fewer grams of sugar than the other kids.

"These laws were specifically designed to improve students' intake at school, and that is exactly what the evidence suggests they achieved," Taber told Reuters Health in an email.

The kids don't necessarily choose healthy foods over unhealthy foods, however.

The Californians ate the same proportion of vitamins and minerals as the kids from other states.

"All states could focus on providing more healthy foods in schools, in addition to banning high-fat, high-sugar, high-calorie foods and beverages," said Taber.

Taber said other states have taken action to restrict the least healthy foods in school, but California has been the one of the most ambitious in terms of also offering healthier foods.

"They should definitely be applauded for their actions. But I think the lesson is that even their laws were only a starting point," Taber said.

The U.S. Department of Agriculture (USDA) is developing federal standards for what foods kids would have access to in vending machines or from a la carte lines at schools.

A recent poll found that most parents support the stricter guidelines (see Reuters Health story of April 19, 2012).

The USDA has already set standards for school lunches that are expected to make the meals healthier.

Crawford said the study is a good first step in examining the dietary benefits of California's laws.

"I'm glad they did the first step here to look at the nutritional benefits," she told Reuters Health. "Because they are benefits, we just need to go further."

SOURCE: bit.ly/KfPcUS Archives of Pediatrics and Adolescent Medicine, May 2012.

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