Page 80 - Special Issue: Healthy Baby
P. 80

A study of      the risk of birth defects. This belief can be  of the third trimester. One study conducted in

           over 10,000        traced to a single study published in 1995 that  Britain showed that 36 percent of new mothers
                              purportedly found an increase in the risk of birth  and 32 percent of newborn infants had no detect-
               infants in     defects among mothers consuming more than  able vitamin D in their blood; another showed
                  Finland     10,000 IU per day. As discussed in the sidebar  that 60 percent of infants born to white mothers
                              below,  there  are  several  important  flaws in  in the spring and summer had levels under 8
                 showed       this study. Every other published study on this  nanograms per milliliter (ng/mL), a level that is

              that direct     subject shows this amount of vitamin A to be  overtly deficient. 32
        supplemention         safe—indeed, one major study of over 25,000     In 1963, the American Academy of Pediatrics
                              births showed that daily doses of vitamin A up  acknowledged the increased need for vitamin
            of 2,000 IU       to 40,000 IU cut the risk of birth defects in half.  D during the third trimester of pregnancy. The
              vitamin D           Considering the ubiquitous role of vitamin  Academy lamented the lack of data elucidating

              per day to      A in the development of every organ system of  the precise amount of this need and suggested that
                              the body and how tightly the body regulates the  400 IU per day would cover the requirements of
          infants in the      level of the activated form, we should expect a  mother and fetus. 28
             first year of    generous helping of vitamin A-rich organs and     In 1997, however, the Institute of Medicine
                              animal fats to help perfect fetal development, not  declared that the transfer of vitamin D from the
            life virtually    to throw it off course. The preponderance of the  mother to the fetus is so small that the mother’s

        eradicated the        evidence suggests that this is the case.   vitamin D status is not affected. Citing a 1978
          risk of type 1      VITAMIN D                                  study showing that the average vitamin D level
                                                                         of pregnant women consuming small amounts
                diabetes          Late in the third trimester, the fetal skeleton  of vitamin D at high latitudes was 9.1 ng/mL
          over the next       enters a period of rapid growth that requires calci-  (25 percent under the level required to protect
                              um, phosphorus and vitamin D. An infant born six  against overt deficiency) the Institute concluded
                30 years.     weeks prematurely has laid down only half the cal-  that “there is no additional need to increase the
                              cium into its bones as an infant carried to term.28  vitamin D age-related [adequate intake] during
                              There is evidence that vitamin D plays a role in  pregnancy above that required for non-pregnant
                              lung development,  and it probably plays a much  women.” This conclusion is strange, not only
                                             29
                              larger role in fetal development in general due to  because many of the mothers in this study must
                              vitamin D’s interaction with vitamin A. At birth,  have had vitamin D levels below the average, but
                              the infant’s blood level of vitamin D is closely  because the average level itself was already defi-
                              correlated to that of the mother. 30,31  Adequate  cient. The Institute set the recommended intake
                              levels of vitamin D protect the newborn from  at 200 IU, which it rather dubiously supposed
                              tetany, convulsions and heart failure. 29  “may actually represent an overestimate of true
                                  The rapid skeletal growth that occurs in late  biological need.” 33
                              pregnancy taxes the vitamin D supply of the     In 2003, the American Academy of Pediat-
                              mother and her blood levels drop over the course  rics’ Committee on Nutrition and its Section on



                                     IS THE PREGNANCY RDA FOR VITAMIN A ADEQUATE?
               The RDA of vitamin A for pregnant women is only 2,600 IU—just 300 IU more than the RDA for women who are
           not pregnant. To obtain this figure, the scientists at the Institute of Medicine (IOM) made the following calculation: first,
           they ascertained from previous reports the amount of vitamin A stored in the livers of fetuses that were spontaneously or
           voluntarily aborted between 37 and 40 weeks; second, they doubled this figure, assuming that half of the fetal vitamin
           A stores exist in the liver; and third, they divided this amount over the number of days in the last trimester, during which
           they presumed this vitamin A would accumulate. 20
           There are several problems with this calculation. Since the fetuses were aborted, we have no idea what their future
           health would have been like—their visual acuity, their hearing, their intelligence, their facial and dental features, their
           reproductive health, or their length of life. And the function of vitamin A, of course, is not to be stored but to be used.
           The fetus does not simply hold on to vitamin A to use it after birth, but rapidly uses and metabolizes it to regulate the
           entirety of its growth and development. Granted, the IOM acknowledges that it has only used this data because better
           data do not exist—yet it is important to emphasize just how little the data tell us.


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