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Expectant Moms Need Milk's Vitamin D

Lower-Birth-Weight Babies Linked to Too Little Milk During Pregnancy
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WebMD Health News

April 24, 2006 -- Expectant mothers who don't drink milk aren't getting enough vitamin D -- and it's affecting their babies, a Canadian study shows.

Babies born to mothers who do not drink milk weigh a bit less than those born to moms who do, report Kristine G. Koski, PhD, RD, director of the School of Dietetics and Human Nutritionat McGill University in Montreal, and colleagues.

"You can actually reduce an infant's birth weight by reducing the mother's milk intake," Koski tells WebMD.

Koski's team studied 279 healthy pregnant women and their newborns. The difference in weight wasn't large. Kids born to mothers who did not drink milk averaged 7.5 pounds, versus the 7.8-pound babies born to the average milk drinker.

But by not drinking milk, mothers got far too little vitamin D. And data analysis shows that it was vitamin D -- not calcium or any other milk-related nutrient -- that accounted for the infants' lower weight.

A fraction of a pound in body weight difference does not sound like much, but it's a danger sign, says vitamin D expert Bruce W. Hollis, PhD, of the Medical College of South Carolina. Hollis's editorial accompanies the Koski report in the April 25 issue of the Canadian Medical Association Journal.

"The results the Koski team found were surprising, given the extremely low levels of vitamin D in even the milk drinkers," Hollis tells WebMD. "It shows how important vitamin D is."

There are about 2.25 micrograms of vitamin D in a cup of milk. The Koski study, Hollis says, shows that for each daily microgram of vitamin D a mother consumes, her baby's birth weight will increase by 11 grams -- more than a third of an ounce. That's a little less than one extra ounce of birth weight for every daily cup of milk a mother drinks.

"Vitamin D is important in the development of the skeleton. [A mother's vitamin D level] impacts the baby 10 years out from birth," Hollis says. "Whether in the womb or later in life, vitamin D deficiency is dangerous."

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