Academic journal article Bulletin of the World Health Organization

Contribution of Breastfeeding to Vitamin A Nutrition of Infants: A Simulation Model. (Research)

Academic journal article Bulletin of the World Health Organization

Contribution of Breastfeeding to Vitamin A Nutrition of Infants: A Simulation Model. (Research)

Article excerpt

Voir page 85 le resume en francais. En la pagina 86 figura un resumen en espanol.

Introduction

It is estimated that subclinical vitamin A deficiency affects 75-140 million preschool-age children in developing countries (1). Such deficiency increases susceptibility to infection and the probability of death. A meta-analysis of randomized control trials indicated that improvement in the vitamin A status of children aged 6-59 months reduced mortality by 23% in populations at risk of vitamin A deficiency (2). Most of this mortality occurred before the age of 2 years. Data from eight field trials showed that the mortality reductions in children aged 6-24 months comprised over 70% of the number of lives saved through improving the vitamin A status of children aged 6-59 months (2).

Breastfeeding can be highly beneficial in this connection because of the high levels of retinol and other factors normally found in breast milk (3). The promotion and protection of breastfeeding is therefore an important strategy in the prevention of vitamin A deficiency in infancy. If maternal vitamin A status is poor, however, even breastfed infants are likely to become subclinically deficient by about 6 months of age (4, 5). Maternal supplementation with a high dose of vitamin A shortly after delivery increases its concentration in breast milk (6). Quantification of the roles of these strategies can be expected to help child health advocates promote both optimal breastfeeding practices and improved maternal vitamin A nutrition in populations at risk of vitamin A deficiency.

In this paper we report calculations of the contribution of breastfeeding to infant vitamin A requirements under different conditions. Model inputs included the concentration of vitamin A in breast milk, the quantity of breast milk consumed, and the vitamin A requirements of infants. Estimates derived from the literature were used in order to simulate and compare different conditions, thus providing a measure of the benefits potentially obtainable from improvement in both maternal vitamin A status and breastfeeding practices.

Methods

Vitamin A level in breast milk

The level of vitamin A in breast milk varies with maternal vitamin A status and the stage of lactation. In well-nourished mothers, colostrum contains 151 [micro]g/100 ml, transitional milk contains 88 [micro]g/100 ml and mature milk contains 75 [micro]g/100 ml of vitamin A (7). The US National Research Council (8) gives the range of vitamin A levels in the milk of well-nourished women in the USA and Europe as 40-70 [micro]g/100 ml. The concentration of vitamin A in the mature milk of unsupplemented mothers in developing countries was found to be about half that in the milk of such mothers in developed countries (5). Lower intakes of animal foods in developing countries probably explain much of this difference. However, other contributory factors may include lower intakes of dietary fat (needed for optimal absorption and utilization of vitamin A and precursor carotenoids), higher intakes of dietary fibre (which may reduce the bioavailability of carotenoids), infections (which can increase metabolic demand), and iron or zinc deficiencies.

Differences in regional averages do not reveal the range of retinol concentrations in breast milk observed among poorly nourished mothers. Although the weighted average reported for developing countries by Newman (5) is 333 [micro]g/1 (5), some populations have lower average levels and many women have retinol levels lower than this. For example, 79% of 72 unsupplemented mothers in rural Bangladesh had retinol levels < 300 [micro]g/l in their mature (3-month) breast milk (9). In Indonesia, one study reported that 33% of unsupplemented mothers participating in a clinical trial had retinol <300 [micro]g/l at three months (10), while another found that the control group had mean retinol concentrations in their breast milk of only 175 [micro]g/l (11). …

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