Osteoporosis gene linked to calcium absorption  in healthy children

Identifying genetic factors that influence calcium absorption and bone density today might help tomorrow's children avoid the pain of osteoporosis.

Scientists at the USDA/ARS Children's Nutrition Research Center at Baylor College of Medicine have found that genetic variation in the Fok1 site of the vitamin D receptor gene predicts differences in dietary calcium absorption and bone density in healthy children.  A Fok1 variation called the ff genotype has been associated with lower bone mass in adults and children.

"No one study can identify what causes osteoporosis, but this study provides further evidence that genetic factors can lead to identifiable changes in the way the body uses calcium," said Dr. Steven Abrams, an associate professor of pediatrics at Baylor.  "But, further studies are needed to determine whether these gene-related changes lead to an increased risk of osteoporosis."

Abrams studied the relationship between the three genetic variations of Fok1, known as FF, Ff and ff, and markers of calcium status in 72 healthy Caucasian, African-American and Mexican-American children between 7 and 12 years of age.  The children were tested for calcium absorption, bone mineralization and bone density. 

"We found that children who had certain genotypes had lower bone density and a lower ability to absorb dietary calcium," Abrams said.  Results showed that children with the FF genotype absorbed over 40 percent more calcium from their diet than those with the ff genotype, and 17 percent more than those with the Ff genotype.  The FF genotype children also had significantly greater bone density measurements. "Peak bone mass occurs in early adulthood and is considered an important determinant of osteoporosis risk later in life," he said.

Many factors, including diet and exercise, can affect bone density.  But, knowing that children with certain genotypes absorb calcium less efficiently is a step towards understanding why some groups appear more likely to develop osteoporosis.  "Leaning how genetics affects calcium metabolism can help lay the groundwork for future studies designed to identify specific risk factors for osteoporosis and develop intervention strategies," Abrams said.

Editor's Note: Vitamin D Receptor Gene Fok1 Polymorphism Predicts Calcium Absorption and Bone Mineral Density in Children. J Bone Miner Res 1999; 14: 740-746.

Calcium
Osteoporosis