Blood levels found too low to supply fetuses and newborns; standard prenatal multivitamins do not meet the need
by Craig Weatherby
Last month, we reported on a study which indicated that nursing women should be taking ten times the US RDA for vitamin D—4,000 IU instead of 400 IU—in order to ensure that their infants get enough of this critical nutrient (See “Nursing Women May Need More Vitamin D”).
Now a study from University of Pittsburgh extends the finding to pregnant women, whose umbilical blood supply constitutes their fetuses' sole food source.
The researchers explained their motive for conducting a study of expectant mothers' vitamin D status: “In utero or early-life vitamin D deficiency is associated with skeletal problems [rickets], type 1 [childhood, insulin-dependent] diabetes, and schizophrenia.”
The incidence of rickets (bent bones) is rising in the US, especially among exclusively breast-fed African-American children. (The melanin pigment in dark skin blocks the UV sunrays that trigger production of vitamin D in the skin.)
In adulthood, higher vitamin D tissue levels help prevent osteoporosis, cancer, and diabetes, and may even help prevent and fight the flu (Go to our newsletter archive and search for “vitamin D”).
Study shows drastic “D” deficiency in pregnant women
Blood from 400 pregnant black and white women (200 of each group) residing in Pittsburgh—and their newborn babies' umbilical cords—was collected between 1997 and 2001 (Bodnar LM et al 2007).
Recently, a team led by assistant professor Lisa Bodnar, Ph.D. analyzed the blood and found that 56.4 percent of white babies and 46.8 percent of African-American newborns had insufficient vitamin D levels at birth.
Worse yet, 9.7 percent of white babies and 45.6 percent of African-American newborns were deficient in vitamin D at birth.
The reason was clear: 83.3 percent of the African-American mothers, and 47.1 percent of the white mothers, had insufficient or deficient blood levels of vitamin D at delivery.
And these shortages occurred even though more than 90 percent of the women took prenatal vitamins during pregnancy.
These findings further strengthen vitamin D experts' case for raising the US RDA for vitamin D—from 400 IU to about 1,500 IU—and for raising the upper intake safety limit on food and supplements containing vitamin D, from 2,000 to 4,000 IU or more.
Dr. Bodnar's team called for advising mothers to take doses well above the RDA (400 IU).
Ideally, they would have specified vitamin D3—the form in animal foods and humans—as it is safer and more effective than the D2 form found in plants and most supplements.
For example, a study in Finland found that vitamin D2 supplements failed to have much impact on the vitamin D status of prepubescent girls in that sun-deprived country (Lehtonen-Veromaa M et al 2002).
Wild salmon seems better than supplements
Higher levels of supplementation make sense as insurance, but there's a great way to help ensure adequate vitamin D intake among mothers while giving them ample amounts of child-development-enhancing omega-3s at the same time.
As we reported earlier this week, wild Pacific Salmon top the list of fish tested for vitamin D content by Boston University researchers, with an unmatched 988 IU per 3.5 ounce serving. (They did not specify the species of Pacific salmon: see “Wild Salmon Affirmed as Top Vitamin D Source.”)
This was over 400 percent more vitamin D than the BU team found in farmed Atlantic salmon (245 IU).
We should note that there are seasonal and geographical variations in the vitamin D content of salmon and other species of fish.
A 2005 test of wild Sockeye Salmon purchased for Vital Choice showed a somewhat lower but still extremely hefty 687 IU per serving: an amount that put it at the top of all three salmon species we tested (Sockeye, Silver, and King).
The point is that on average, wild salmon seem to beat all other fish for vitamin D content. Together with their superior omega-3 content, this makes wild salmon of any species ideal food for mothers and babies.
- Bodnar LM, Simhan HN, Powers RW, Frank MP, Cooperstein E, Roberts JM. High prevalence of vitamin D insufficiency in black and white pregnant women residing in the northern United States and their neonates. J Nutr. 2007 Feb;137(2):447-52.
- Lehtonen-Veromaa M, Mottonen T, Nuotio I, Irjala K, Viikari J. The effect of conventional vitamin D(2) supplementation on serum 25(OH)D concentration is weak among peripubertal Finnish girls: a 3-y prospective study. Eur J Clin Nutr. 2002 May;56(5):431-7.