Selenium Requirements During Pregnancy and Lactation

Reference from the joint report of FAO/WHO expert consultation on Human Vitamins and Minerals verbatim.

90. Scientific Committee for Food. 1993. Nutrient and Energy Intakes for the European Community. Report of the Scientific Committee for Food, Thirty First Series. Office for Official Publications of the European Communities, Brussels.

91. Department of Health. 1991. Dietary Reference Values for Food Energy and Nutrient Intakes for the United Kingdom. Report on Health and Social Subjects No.41. London, HMSO.

92. Netherlands Food and Nutrition Council. 1989. Recommended Dietary Allowances. The Netherlands. The Hague.

Data from balance experiments are not sufficiently consistent for defining the increase of selenium needed to support foetal growth and development during pregnancy. For this reason the European Union Scientific Committee for Food (90), the UK Committee on Medical Aspects of Food Policy (91), and the Netherlands Food and Nutrition Council (92) have suggested that the component of selenium needed for human pregnancy is obtained by an adaptive increase in the efficiency of absorption of dietary selenium rather than by an increased dietary demand.

47. World Health Organization. 1998. Complementary Feeding of Young Children in Developing Countries \\WHO/NUT/98.1. Geneva, WHO.

86. WHO/FAO/IAEA. 1996. Trace elements in Human nutrition and health. Geneva. World Health Organization.

Others, contesting this view, have attempted to predict the increase of dietary selenium needed for pregnancy by factorial estimation of the likely quantity of selenium incorporated into the tissues of the foetus (47, 86). Such estimates have assumed that the total products of conception amount to 4.6–6 kg lean tissue with a protein content of approximately 18.5–20 percent.

49. Williams, M.M.F. 1983. Selenium and glutathione peroxidase in mature human milk. Proceedings of the University of Otago Medical School, Dunedin, 61: 20-21.

52. Millar, K.R. & Sheppard, A.D. 1972. α-Tocopherol and selenium levels in human and cow's milk. NZ J. Sci., 15: 3-15.

73. Levander, O.A. & Morris, V.C. 1984. Dietary selenium levels needed to maintain balance in North American adults consuming self-selected diets. Am. J. Clin. Nutr., 39:809-815.

If, as appears to be a reasonable assumption, the selenium content of this protein resembles that of a skeletal muscle, growth of these tissues could account for between 1.0 and 4.5 μg/day of selenium depending on whether the analyses reflect consumption of diets from a low-selenium (but non-pathogenic) environment (e.g., New Zealand [49, 52]) or from a region with relatively high selenium intakes (e.g., United States, Table 50 [73]).

86. WHO/FAO/IAEA. 1996. Trace elements in Human nutrition and health. Geneva. World Health Organization.

Typically such estimates have assumed an 80 percent absorption and utilisation of dietary selenium from which it would appear reasonable to estimate that allowing for a variability of estimates (CV 12.5 percent) an increase of 2 μg/day would be appropriate for the second trimester and 4 μg/day would be appropriate for the third trimester of pregnancy (Table 52).

47. World Health Organization. 1998. Complementary Feeding of Young Children in Developing Countries \\WHO/NUT/98.1. Geneva, WHO.

As is evident from Table 49 the selenium content of human milk is sensitive to changes in maternal dietary selenium. The increase of maternal dietary selenium needed to meet requirements for lactation has been estimated from the estimated RNI for infants aged 0–6 months and 7–12 months. 

It is assumed that the selenium of maternal milk is used with an efficiency of 80 percent, and a SD of 12.5 percent is assumed. For the period 0–6 months it is estimated that the infant must receive 6 μg/day from human milk. The increase of maternal dietary selenium required to produce this will be 6 x 100 + (2 x SD) = 9 μg/day. The corresponding increase needed to meet the infant RNI of 10 μg/day for ages 7–12 months will be 16 μg/day. Added to the non-pregnancy maternal RNI of 26 μg/day, the total RNI for lactation during the first 6 months post-partum will be 35 μg/day and for months 7–12 will be 42 μg/day (Table 52).

86. WHO/FAO/IAEA. 1996. Trace elements in Human nutrition and health. Geneva. World Health Organization. 

As implied by the data in Tables 48, 49 and 50, agricultural growing practices, geologic factors, and social deprivation enforcing the use of an abnormally wide range of dietary constituents may significantly modify the variability of dietary selenium intakes. If accumulated experience suggests that the CV of selenium intake may be 40 percent or more and tabulated rather than analysed data are used to predict the dietary content of selenium, the selenium allowance may have to be increased accordingly or assessed by using the WHO-FAO-IAEA technique (86).