Women who have habitually low levels of
calcium in their diet undergo significant changes in bone
calcium turnover during pregnancy and lactation, according
to the results of a new study.
Dr. Janet C. King, of Children's Hospital Oakland Research
Institute, California, and colleagues examined calcium
levels during pregnancy and early lactation in 10 Brazilian
women. The average level of dietary calcium was 463 milligrams
per day, the researchers report in the American Journal
of Clinical Nutrition.
The women were given a form of calcium that could be
easily detected as it moved through the body, so bone
calcium turnover could be monitored in different compartments.
Evaluations were performed during early pregnancy (10
to 12 weeks), late pregnancy (34 to 36 weeks), and early
lactation (7 to 8 weeks after birth).
A significant increase in the rate of bone calcium deposition
was observed from early to late pregnancy, the researchers
found. Compared with early pregnancy, the rates of bone
calcium resorption were higher during late pregnancy and
early lactation.
They also observed a positive relationship between bone
calcium turnover and dietary calcium from early pregnancy
to early lactation. Dietary levels of calcium and levels
of insulin-like growth factor 1 explained 68 to 94 percent
of the variability in bone calcium balance.
Summing up their findings, King and colleagues say that
a positive bone calcium balance occurred only during late
pregnancy, whereas calcium losses of about 90 milligrams
per day was seen during early pregnancy and early lactation.
The researchers believe that further studies should address
the effects of higher levels of calcium in the diet or
calcium supplements on maternal and fetal bone mass, long-term
changes in bone mass and calcium levels during pregnancy,
lactation and after lactation in other groups of women
who have low dietary calcium levels.
SOURCE: American Journal Clinical Nutrition, February
2006.
