Dr Nick Harvey from the MRC Epidemiology Resource Centre and University of Southampton, told delegates at the 35th European Symposium on Calcified Tissues in Barcelona that patterns of bone growth in the first few years of life can strongly influence the onset of osteoporosis decades later.

The study, part of a larger programme of research into the early life origins of osteoporosis under the leadership of Porfessor Cyrus Cooper, involved more than 12,500 non-pregnant women aged 20-34, recruited between 1998 and 2002 into the Southampton Women's Survey. The women underwent comprehensive assessment of diet, lifestyle and body measurements before, and for those who conceived (now around 3000 women), during pregnancy. A subset of their children had measurement of bone mass at birth and four years old, and additionally the four year old children underwent similar assessment of diet, lifestyle, health and body measurements. In this group of 250 children and their mothers, Dr Harvey and his colleagues used this information to determine what influences a child's bone growth compared to that in other children in the group of the same age.

"We wanted to find out what factors determine whether a child with lower bone mass at birth catches up compared with other children in later life. We think that diet during childhood may make a difference," said Dr Harvey. "In our study, catch up in bone mass compared with other children in the group was associated with drinking more milk in childhood. This continued after we took into account genetic factors such as the mother's height, suggesting that both the genetic make-up of the child and factors such as diet are important for bone growth."

Bone mass peaks between the ages of 20 - 30 years. Babies and children who are underweight and undernourished are likely to have a lower bone mass in early adulthood than normal which would make them more vulnerable to osteoporosis in later life.

After peak bone mass is reached in early adulthood, bone mass delines with age, particularly after the menopause in women. research has shown that the highter the peak bone mass gained, the lower the risk of osteoporosis in later life. "Thus factors which influence bone growth from conception to peak are likely to be curcial in reducing the risk of fractures in older age," explained Dr Harvey.

The Southampton data suggest the importance of both genetic and envirnomental factors in determining the trajectory of bone growth. "The big question now is to find way to improve bone mass to reduce the risk of osteopporosis," he said. The team is now studying whether viatmin D supplements could help.

"Our research shows that the biological processes involved with bone growth start before the child is even born. It is, therefore, important to consider what can be done to improve bone health throughout the life time of the individual. Since this starts when the baby is conceived, parental health and lifestyle at conception and during pregnancy are likely to be vital factors," Dr Harvey concluded.

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