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Magnesium may be more important to kids’ bone health than calcium – May 2013

Highlight: dietary magnesium intake, but not calcium intake, was significantly associated with both total body bone mineral content and density

2715.3 Magnesium, but Not Calcium Intake

Is Significantly Association with Bone Mineral Status in 4 to 8 Year Old Children
Steven A. Abrams, Zhensheng Chen, Keli M. Hawthorne. Pediatrics/CNRC, Baylor College of Medicine, Houston, TX.

BACKGROUND: Magnesium (Mg) is a key factor in bone health, but few studies have evaluated magnesium intake or absorption and their relationship with bone mineral content status in children, especially those who are pre-pubertal.

OBJECTIVE: Our primary objective was to evaluate magnesium metabolism in children and determine the relationship between magnesium intake and absorption and bone mineral status. Our secondary goal was to determine fractional and total magnesium absorption and estimated retention and compare these with recommendations including current Dietary Reference Intake values.

DESIGN/METHODS: We measured Mg intake, absorption and urinary excretion in a group of 63 children age 4 to 8 yrs of age. Absorption was determined using a dual-tracer stable isotope method in which 25Mg was given intravenously and 26Mg given orally with subsequent collection of a 72-hour urine and calculation of fractional dietary absorption from the relative recovery of the oral versus the intravenous tracer. Dietary Mg intake was determined using a 3-day weighed diet including one in-patient and two out-patient days. Bone mineral content and density were determined by total body Dual-Energy X-ray Absorptiometry.

RESULTS: We found a small, but significantly greater Mg absorption efficiency in males than females (65 ± 11% vs 59 ± 8%, p = 0.02, Data are Mean ± SD) but no difference in estimated net Mg retention (37 mg/day in both males and females) due to higher urinary Mg in the males. Relating dietary Mg intake to estimated Mg retention showed that an intake of approximately 130 mg/day, slightly above the current Estimated Average Requirement of 110 mg/day led to a net average retention of 10 mg/day, the likely growth-related need for net positive retention in this age group. Covariate analysis showed that dietary magnesium intake, but not calcium intake, was significantly associated with both total body bone mineral content and density (P < 0.01 for each), whereas gender and race were not significantly related to bone mineral outcomes.

CONCLUSIONS: These results demonstrate that magnesium intakes in small children in the United States mostly meets dietary requirements and that gender differences exist in magnesium absorption and excretion. Dietary Mg intake may be an important, relatively unrecognized, factor in bone mineral accretion in children.

Press Release

Parents are advised to make sure their children drink milk and eat other calcium-rich foods to build strong bones. Soon, they also may be urged to make sure their kids eat salmon, almonds and other foods high in magnesium — another nutrient that may play an important role in bone health, according to a study to be presented Sunday, May 5, at the Pediatric Academic Societies (PAS) annual meeting in Washington, DC.

“Lots of nutrients are key for children to have healthy bones. One of these appears to be magnesium,” said lead author Steven A. Abrams MD, FAAP, professor of pediatrics at Baylor College of Medicine in Houston. “Calcium is important, but, except for those children and adolescents with very low intakes, may not be more important than magnesium.”

While it is known that magnesium is important for bone health in adults, few studies have looked at whether magnesium intake and absorption are related to bone mineral content in young children. This study aimed to fill that gap.

Researchers recruited 63 healthy children ages 4 to 8 years old who were not taking any multivitamins or minerals to participate in the study. Children were hospitalized overnight twice so their calcium and magnesium levels could be measured.

Participants filled out food diaries prior to hospitalization. All foods and beverages served during their hospital stay contained the same amount of calcium and magnesium they consumed in a typical day based on the diaries. Foods and beverages were weighed before and after each meal to determine how much calcium and magnesium the subjects actually consumed. In addition, parents were given scales to weigh their child’s food for three days at home after the first inpatient stay and for three days at home prior to the second inpatient stay so that dietary intake of calcium and magnesium could be calculated accurately.

While hospitalized, children’s levels of calcium and magnesium were measured using a technique that involved giving them non-radioactive forms of magnesium and calcium, called stable isotopes, intravenously and orally. Urine was collected for 72 hours. By measuring the stable isotopes in the urine, the researchers could determine how much calcium and magnesium were absorbed into the body. Bone mineral content and density were measured using total body dual-energy X-ray absorptiometry.

Typically, when parents think about their children’s health, they don’t think about their bones. But building healthy bones by adopting healthy nutritional and lifestyle habits in childhood is important to help prevent osteoporosis and fractures later in life.

Osteoporosis, the disease that causes bones to become less dense and more prone to fractures, has been called “a pediatric disease with geriatric consequences,” because the bone mass attained in childhood and adolescence is an important determinant of lifelong skeletal health. The health habits your kids are forming now can make, or literally break, their bones as they age.

Why Is Childhood Such an Important Time for Bone Development?
Bones are the framework for your child’s growing body. Bone is living tissue that changes constantly, with bits of old bone being removed and replaced by new bone. You can think of bone as a bank account, where (with your help) your kids make “deposits” and “withdrawals” of bone tissue. During childhood and adolescence, much more bone is deposited than withdrawn as the skeleton grows in both size and density.

For most people, the amount of bone tissue in the skeleton (known as bone mass) peaks by their late twenties. At that point, bones have reached their maximum strength and density. Up to 90 percent of peak bone mass is acquired by age 18 in girls and age 20 in boys, which makes youth the best time for your kids to “invest” in their bone health.

Results showed that the amounts of magnesium consumed and absorbed were key predictors of how much bone children had. Dietary calcium intake, however, was not significantly associated with total bone mineral content or density.

“We believe it is important for children to have a balanced, healthy diet with good sources of minerals, including both calcium and magnesium,” Dr. Abrams concluded.

See also VitaminDWiki

Magnesium may be more important to kids’ bone health than calcium – May 2013        
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