Although calcium usually gets top billing when it comes to bone health, fruits and vegetables may also promote stronger bones in girls, new study findings suggest.
The study of 56 white girls ages 8 to 13 found that those who ate at least three servings of fruits and vegetables each day had bigger bones than their peers. Researchers suspect that a produce-rich diet helps limit the body's excretion of calcium from the bones.
Several studies in adults have tied fruit and vegetable consumption to greater bone density, possibly due to nutrients commonly found in these foods, such as potassium, beta-carotene, vitamin C and magnesium. There's also evidence that fruits and vegetables lower the excretion of calcium in the urine.
This is because fruits and vegetables act as "base" foods that help counteract the acid that is produced when other foods, such as proteins and grains, are metabolized. It's thought that when a diet lacks such acid-buffering foods, the bases present in bone, including calcium, may have to come to the rescue.
One study has suggested that the vast majority of calcium excreted in urine comes from bone stores rather than dietary intake.
But little is known about produce intake, urinary calcium and bone health in children, according to the authors of the new study, led by Dr. Frances A. Tylavsky of the University of Tennessee in Memphis.
She and her colleagues had the girls and their parents record the subjects' food intake on three different days over a one- to two-year period. The researchers also used X-rays to measure the girls' bone size, and took urine and blood samples.
They found that compared with girls who ate fewer than three servings of fruits and vegetables per day, those who ate more had greater bone area overall, as well as greater bone area in the wrist. These girls also excreted less calcium in their urine, according to findings published in the American Journal of Clinical Nutrition.
The researchers suspect that this "lower calcium output" is the reason for the fruit and veggie eaters' bigger bones. Though it's possible, Tylavsky told Reuters Health, that the higher intakes of produce were a marker of an overall healthier diet.
However, the study found no difference in protein or calcium intake between girls who ate three daily servings of produce and those who ate less. Nor were the larger bones a product of the high-consumption group getting more exercise.
Still, the researchers point out, the study was small and included only white girls from affluent families. Whether the findings extend to all groups, and whether fruits and vegetables ultimately affect a person's peak bone mass, remains unknown.
Tylavsky noted that peak bone mass--the maximum bone density a person achieves--also depends largely on genetics and exercise.