Vitamin D Levels During Pregnancy Predict Kids' Bone Health
Moms who take extra supplements may protect offspring from osteoporosis, study suggests
By Amanda Gardner
FRIDAY, Jan. 6 (HealthDay News) -- 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.
The National Institutes of Health has more on vitamin D.
SOURCES: Stephen Honig, M.D., director, Osteoporosis Center, Hospital for Joint Diseases, New York City; Loren Wissner Greene, M.D., clinical associate professor, medicine, New York University School of Medicine, and co-director, Bone Density Unit, New York University; Jan. 7, 2006, The Lancet
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