Can bones remember? According to new research presented at the IOF World Congress on Osteoporosis in Toronto, Canada they can. Not in the traditional sense, of course, but in that their vulnerability to osteoporosis and fractures depends on how the bones developed during pregnancy and childhood, according to Dr. Kassim Javaid of the MRC Epidemiology Resource Center, in Southampton, UK (conference abstract P108).

These findings come at a time when IOF is preparing for World Osteoporosis Day 2006. The event, which will be celebrated on October 20 by IOF's members in 85 countries, will focus for the first time on the role of nutrition in building bones, with the theme "Bone Appetit."

Poor skeletal growth during infancy can increase risk of later-life fractures

Javaid and colleagues previously demonstrated an association between poor skeletal growth in older children and increased fracture risk among the elderly. Now, the researchers find that poor skeletal growth during infancy and early childhood also enhances the risk of future fractures. "Now we have evidence that the bone mass you have at the age of 80 reflects what you started with very early in life."

To produce these findings, Javaid et al. compared weight and length data from 13,345 children (6,370 women) born in Helsinki between 1934 and 1944--both at birth and at varying childhood intervals--with their recorded hip fractures during old age. The researchers found that children whose weight was low relative to their length during infancy and early childhood had more hip fractures later in life.

Javaid cautions that weight's source--meaning the amount contributed by fat versus muscle mass--was not investigated. Therefore, children won't necessarily lessen their risk of osteoporosis by gaining fat, he said. Moreover, separate findings from a study of Caucasian and Chinese adults, led by Dr. Hong-Wen Deng of the University of Missouri, in Kansas, City (Conference abstract P152), suggest that weight derived from muscle mass contributes to bone density while excess fat contributes to bone loss, for unknown reasons. "The distinction [between the roles of muscle mass and fat in bone strength] has profound implications for public health and we're looking into that now," Javaid said. "The key point is that you want to make sure children maintain adequate growth as they get older."

Maternal Vitamin D Levels and Infant Bone Density

In a different study, Nicholas Harvey of the MRC Epidemiology Resource Center, in Southampton, UK, offered evidence showing that children born to mothers with higher vitamin D levels during pregnancy have stronger skeletons (conference abstract OC9). Focusing on subjects from the Southampton Women's Survey, which includes cohort of women aged 20-34, Harvey and colleagues compared maternal vitamin D levels during late pregnancy with infant bone density in 556 babies (286 males) soon after birth. They also took placental samples and analyzed them for levels of calcium transporter, which is a protein that carries calcium from the mother to the developing child. Like vitamin D, calcium is necessary for building strong bones.

According to Harvey, the study yielded a pair of complementary findings:

First, women who were vitamin D deficient tended to give birth to girls with low-density bones. Harvey said he's unsure why the finding was limited to girls, but he adds the gender difference might disappear in a larger study.

In a second finding, the researchers showed that rising levels of calcium transporter predict higher infant bone density. "What we hypothesize is that the mother's vitamin D levels somehow influence the amount of calcium transporter in circulation," Harvey said. "And if calcium transporter levels are low, then the infants don't get enough calcium, and their bones become weaker as a result."

Despite the finding, Harvey was reluctant to propose that women should take vitamin D supplements during pregnancy. That question should be investigated in further research, he said. "We think it would be safe but we can't recommend that type of intervention until we study it further."