Vitamin D levels during pregnancy predict kids'
bone health
Mothers who take extra vitamin D while pregnant could be protecting their children
from osteoporosis later in life.
A study appearing in the Jan. 7 issue of The Lancet reports that children born to
mothers with insufficient vitamin D during pregnancy had weaker bones when they
were 9 years old.
"It's not the holy grail, but it's another piece of information that suggests that
events beginning from gestation influence ultimate bone health and bone strength,"
said Dr. Stephen Honig, director of the Osteoporosis Center at the Hospital for
Joint Diseases in New York City. "This is easily correctable, and seems to be something
that comes at no particular cost, either economic or from an adverse-effect standpoint."
"It's very interesting and very suggestive," added Dr. Loren Wissner Greene, a clinical
associate professor of medicine at New York University School of Medicine and co-director
of the Bone Density Unit at New York University.
Many people show a vitamin D deficiency, and this includes otherwise healthy women
during pregnancy.
Vitamin D is required for optimal calcium absorption, which is critical to bone
growth. The main source of vitamin D is sunlight, and most people don't get enough
of that.
"There has been a recognition that a lot of people in the United States are vitamin
D-deficient in these days of sunscreen," Greene said.
At the same time, accumulating evidence suggests that environmental factors early
in life can influence a person's chance of developing osteoporosis. For instance,
birth weight can predict bone mass later on, while poor intrauterine and childhood
growth are associated with double the risk of hip fracture 60 years later. A mother's
build, nutrition, smoking and physical activity level during pregnancy can also
influence bone mass of the baby at birth.
No one has yet looked at a relationship between the mother's vitamin D status during
pregnancy and skeletal growth of their children. The authors of this study hypothesized
that maternal vitamin D insufficiency during pregnancy had a long-lasting effect
on childhood bone mass.
The researchers studied 198 children born in 1991 and 1992 at a hospital in Southampton,
England. They assessed mothers' body build, nutrition and vitamin D status during
pregnancy; children's body size and bone mass were measured nine years later.
Women who had reduced levels of vitamin D during the later part of their pregnancies
had children with reduced bone-mineral content at 9 years of age.
Women who took vitamin D supplements and who were exposed to more sunshine were
less likely to have a vitamin D deficiency. Reduced concentration of calcium in
the umbilical cord blood was also associated with a reduced bone mass in the offspring.
"Their point is that there may be a programming effect that goes on in utero that
effects calcium and bone accrual," Honig said. "Something happens in the last trimester
that influences the transport of calcium across the placenta, and somehow that situation
changes the developmental period over a prolonged timeframe."
The findings need to be confirmed, but they fit in well with other studies that
have shown that issues early in life, such as low birth weight, can impact osteoporosis
risk later in life.
"These are all things that are lending credibility to the need to think about bone
growth and development as starting from gestation onward, rather than just thinking
about this as diseases that occur after menopause," Honig said. "That's a significant
thing."
The authors suggested that giving vitamin D supplements to pregnant women, especially
if the third trimester occurs during the winter when there is less sunlight, could
contribute to stronger bones in their children."