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."
