VITAMIN D

In the late third trimester, the fetal skeleton enters a period of rapid growth that requires calcium, phosphorus and vitamin D. An infant born six weeks prematurely has laid down only half the calcium into its bones as an infant carried to term.28 There is evidence that vitamin D plays a role in lung development,²⁹ and it probably plays a much larger role in fetal development in general due to vitamin D’s interaction with vitamin A. At birth, the infant’s blood level of vitamin D is closely correlated to that of the mother.^30,31 Adequate levels of vitamin D protect the newborn from tetany, convulsions and heart failure.²⁹

The rapid skeletal growth that occurs in late pregnancy taxes the vitamin D supply of the mother and her blood levels drop over the course of the third trimester. One study conducted in Britain showed that 36 percent of new mothers and 32 percent of newborn infants had no detectable vitamin D in their blood at all; another showed that 60 percent of infants born to white mothers in the spring and summer had levels under 8 nanograms per milliliter (ng/mL), a level that is overtly deficient.³²

In 1963, the American Academy of Pediatrics acknowledged the increased need for vitamin D during the third trimester of pregnancy. The Academy lamented the lack of data elucidating the precise amount of this need and suggested that 400 IU per day would cover the requirements of mother and fetus.²⁸

In 1997, however, the Institute of Medicine declared that the transfer of vitamin D from the mother to the fetus is so small that the mother’s vitamin D status is not affected. Citing a 1978 study showing that the average vitamin D level of pregnant women consuming small amounts of vitamin D at high latitudes was 9.1 ng/mL (25 percent under the level required to protect against overt deficiency) the Institute concluded that “there is no additional need to increase the vitamin D age-related [adequate intake] during pregnancy above that required for non-pregnant women.” This conclusion is strange, not only because many of the mothers in this study must have had vitamin D levels below the average, but because the average level itself was already deficient. The Institute set the recommended intake at 200 IU, which it rather dubiously supposed “may actually represent an overestimate of true biological need.”³³

In 2003, the American Academy of Pediatrics’ Committee on Nutrition and its Section on Breastfeeding issued a joint statement in which they overturned the 40-year position of the Academy advocating 400 IU in favor of adopting the lower so-called “overestimate” of the Institute of Medicine.³⁴

In the second part of this statement, the Academy directed mothers to keep their infants out of the sun, dress them in protective clothing, and liberally cover them in sunblock. In the last part of the statement, it emphasized that breast milk is deficient in vitamin D—making no mention of the fact that the low intake of vitamin D during pregnancy and lactation that it advocates and the practice of keeping infants out of the sun are the precise factors responsible for low vitamin D levels in breast milk and infant vitamin D deficiency.

The Weston A. Price Foundation recommends 2,000 IU per day of vitamin D from cod liver oil, and small additional amounts from fatty fish, shellfish, butter, and lard. Although no studies have directly assessed the use of this dose during pregnancy, a study of over 10,000 infants in Finland conducted between 1966 and 1997 showed that direct supplementation of 2,000 IU per day to infants in the first year of life virtually eradicated the risk of type 1 diabetes over the next 30 years.³⁵