variability is, however, of concern. Clearly, there were individuals within these samples whose dietary intake was either lower or much higher than the mean.
There is much less information concerning the adequacy of dietary intake of other micronutrients, as illustrated in Table 4-6. For example, iodine and vitamins E and K were omitted from the table because no relevant studies included them. Of the micronutrients reported in Table 4-6, vitamins B12, B6, and folate were the only ones studied by more than one group of investigators. The scant data do suggest closer examination of the adequacy of intake of folate and zinc, which were well below the 1989 RDAs in two studies, and of vitamin B6, which was consistently below the 1989 RDA. Clearly, research is needed to provide a more complete nutritional profile of lactating women.
The subcommittee identified only two studies focusing on groups of lactating women defined by factors of culture, ethnic background, life-style, or religion. These were studies of American Indians (Butte and Calloway, 1981) and of vegetarians (Finley et al., 1985) (see Tables 4-5 and 4-6). Among American Indians, vitamin A intake was highly variable and intakes of calcium; magnesium; zinc; and vitamins D, E, and folate appeared to be low. Among all the studies for which results are shown in Table 4-5, mean protein intake was lowest in the vegetarian group but still exceeded the RDA. As expected, the mean vitamin A intake of the vegetarians was the highest. The subcommittee identified only one study of lactating teenagers (Lipsman et al., 1985) and none of lactating women over age 35. The teenagers were found to have mean dietary intakes that met or exceeded the 1989 RDAs (Table 4-5).
Data on the dietary intake of lactating women of low socioeconomic status were also difficult to find. The first national evaluation of the Special Supplemental Food Program for Women, Infants, and Children (WIC) included 179 postpartum women. Of these, less than 79% were breastfeeding at the time that dietary data were collected (at enrollment in WIC, approximately 12 weeks post partum; breastfeeding was a prerequisite for enrollment for most of these women); unfortunately, those maternal nutrient intake values were not presented separately by breastfeeding status (Edozien et al., 1976). In general, the dietary intakes of these women were much lower than the current RDAs. Dietary intake of vitamins B6, B12, and folate was assessed in seven low-income women recruited from a WIC program (Sneed et al., 1981) (Table 4-6). At two stages of lactation, their reported intakes of vitamin B6 were well below the RDA but were comparable to the values for the other groups included in these tables.