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Effects of maternal vitamin A supplementation

Assuming average liver stores in well-nourished populations, the retinol requirement during the first year of lactation can generally be met without increasing vitamin A intake above the normal adult female level. However, vitamin A reserves vary greatly among women and may be precariously low in those whose habitual intake of the vitamin is marginal [12]. For a woman with much smaller stores than normal whose diet barely meets her own requirement, loss of the vitamin in milk could theoretically deplete the stores within a few months [12].

To avoid maternal depletion, therefore, increased intake of vitamin A is suggested during lactation. The National Research Council in the United States recommends an additional 500 RE per day during the first six months of lactation and an extra 400 RE per day during the second six months. The FAO/WHO recommends an extra 350 RE per day throughout lactation. These recommendation are based generally on the expected secretion of retinol into human milk [16].

Lactating women suspected of having low vitamin A stores and/or those unable or unwilling to increase their dietary intake would be expected to benefit from supplementation. Since the concentration of vitamin A in human milk is dependent on the mothers' status, their infants would also be expected to benefit. Potential toxicity from high-dose supplements given directly to the infant is also avoided.

Toxicity considerations

When ingested in large amounts, retinol causes toxicity, including liver damage, bone abnormalities, desquamation, alopecia, diplopia, vomiting, and headaches [15]. It also can cause spontaneous abortion and birth defects, such as deformities of the cranium, face, heart, thymus, kidneys, and cerebral nervous system [15]. Toxicity usually begins to occur in infants with daily doses of 6,000 RE (20,000 IU) and in adults at daily doses of 7,500 RE (25,000 IU) for a prolonged period of time [15]. Birth defects attributed to vitamin A have been reported in the foetuses of women ingesting 7,500-45,000 RE (25,000150,000 IU) daily early in pregnancy [15]. Because of the risk of such congenital malformation, women who are or who might become pregnant should carefully avoid taking supplements exceeding 3,000 RE (10,000 IU) [15]. Except for the livers of mammals and fish, foods consumed in usual quantities do not contain sufficient quantities of vitamin A to induce toxicity. Large quantities of carotenoids in foods may cause some coloration of the skin but are otherwise harmless [15, 16].

Impact on maternal vitamin A status

Whereas massive doses of retinol cause a short-term rise in serum levels in lactating women, the effect of lower-dose supplements appears to depend on the woman's initial status. A number of studies showed a positive impact of supplementation on serum vitamin A levels of lactating women of low socio-economic status assumed to have poor nutrition status [50, 56, 87].

Impact on vitamin A in milk

The efficiency with which vitamin A ingestion by well-nourished mothers is transferred to their milk is not readily defined [16]. However, in vitamin A-depleted women and those with continuous low intakes, dietary supplements generally increase the concentration in milk [16]. These studies are reviewed elsewhere [13].

Since the concentration of retinol in breast milk is generally higher than in the mother's blood, it is assumed that the mammary glands possess active transport systems. However, the absorption capacity of the mammary glands seems to respond to vitamin intake only up to saturation, thereby protecting the infant against vitamin overdose [60]. Although the vitamin A concentration of colostrum or milk can be increased about fourfold by promptly loading the mother with high-dose supplements, the resulting amount secreted into breast milk is nowhere near the 6,000 RE per day toxic dose for infants. Even with daily maternal high-dose supplements ranging from 15,000 to 60,000 RE (50,000-200,000 IU) for several months, the retinol content of human milk remains well below the toxic level [69].

Strategies to control vitamin A deficiency

Several strategies have been recommended and/or employed to control vitamin A deficiency. The relative cost, time course, and sustainability of various approaches are reviewed elsewhere [88-90].

Promotion of breast-feeding

Improving the vitamin A status of lactating women, encouraging exclusive breast-feeding for four to six months of life, and adding appropriate vitamin A-rich weaning foods after that time while breast-feeding continues are important strategies for improving the vitamin A status of infants and young children. Because of the precarious status of preterm and small-for-gestational-age infants, their mothers should receive particular support to enable them to provide their own milk to their infants.

Breast-feeding throughout the infant's first two years of life, with the addition of vitamin A-rich foods to the diet by the age of six months, is particularly important in developing countries where vitamin A deficiency is a recognized public health problem. A study of 2,687 children six months to three years old in Bangladesh reported a 74% reduction in the risk of deficiency among breast-fed children after controlling for a large number of confounding variables [11]. The estimated reduction of risk did not decline with age, as children between 24 and 35 months who were still being breast-fed had a 65% reduced risk. Breast milk proved to be the most important source of vitamin A and fat for rural West African children over one year of age [91]. In rural Bangladesh, when breast milk was not counted, the only dietary recalls that averaged significant amounts of vitamin A were those of children above the age of one year during the mango season [21]. The 14 children between the ages of seven and twelve months who had completely stopped breast-feeding had an average intake of only 3 RE of vitamin A daily. In other words, in the absence of breast milk from their diets, these children received almost no vitamin A. In addition, the younger the age at which breast-feeding was stopped, the more inevitable was the deficiency.

Maternal vitamin A supplementation

The goal for the period of lactation is to maintain the highest vitamin A concentration in breast milk that is compatible with homeostatic control mechanisms [92]. When the woman enters the lactational period in a deficient state and it is not possible to ensure improvement in her dietary intake, the WHO and UNICEF [93] recommend treatment with a daily oral dose of 3,000 RE of retinal for two weeks.

When continued contact with the lactating mother is unlikely, large doses of retinol (200,000-300,000 IU, 60,000-90,000 RE) may be safely given at parturition or within the first postnatal month [92, 93]. This dosage will maintain maternal blood and milk vitamin A levels in the normal range for at least three months and perhaps longer [56]. There is no evidence of risk of toxicity to the mother (except for occasional reports of transient symptoms after high dosing, such as headache, nausea, or vomiting) or her nursling through any of these approaches [92]. It should be noted that smaller, more frequent doses of supplemental vitamin A by fortification of food will achieve similar objectives and be without risk [92].

High-dose supplementation should not be given to lactating women beyond the first postnatal month when there could be a risk of another pregnancy. Beyond that time, supplemental daily dosages of 3,000 RE (10,000 IU) or less will benefit mothers whose diets are inadequate in the vitamin and perhaps better prepare them for a subsequent pregnancy [92].

Nutrition education to increase intake of vitamin A-rich foods

Supplementation is one way to increase the vitamin A intake of deficient lactating mothers and their infants, but dietary modification to increase consumption of vitamin A-rich foods is considered the safest and most sustainable long-term measure. Only small amounts of these foods are necessary to meet daily requirements (table 10).

In many communities, vitamin A-rich foods are under-used in the diets of vulnerable groups, particularly weaning-age children and pregnant and nursing women [2, 21, 95]. Often the least costly and most available green leafy vegetables may be bland, slightly bitter, or too fibrous and therefore considered inappropriate for infants and young children. However, boiling, mashing, straining, and mixing the vegetables with other well-liked foods can make them palatable and digestible [2]. In Indonesia, mothers who claimed that their children never ate greens were asked why this was so. Apart from the category of "other reasons," the majority of mothers with children under two years old thought greens were unhealthy ("too strong") or did not know how to prepare them for young children [95]. These studies suggest the need for social marketing for effective nutrition education.

TABLE 10. Foods that will provide daily vitamin A requirements

Based on requirements from ref. 16 and food-value data from ref. 94.

a. The quantity indicated or any one of the foods shown will supply the requirements.
b. vitamin A averaged from cooked amaranth, beet greens, kale, mustard greens, and spinach.

Data collected in Africa suggest that the major supplier of many micronutrients, particularly vitamin A, is the household or community garden [2]. Most populations at risk of developing deficiency appear to receive most, if not all, of their vitamin A from carotene-containing fruits and vegetables, many of which can be grown in home and community gardens. Such foods tend to be seasonal, but because vitamin A is stored in the body, intake at levels many times the normal daily requirement can ensure adequate liver stores to cover those times when the foods are unavailable.

Food-preservation and cooking methods can reduce vitamin A activity if vitamin-rich foods are subjected to high temperature and sunlight. Cooking a food item whole and then mashing or cutting it is preferable to cutting before cooking. Boiling is preferable to frying, and air-drying food protected from direct sunlight is better than air-drying food directly exposed to sunlight [2]. Properly solar-dried mangoes retain a markedly high level of ß-carotene and can be stored for as long as four to six months without losing their nutrient value [96].

Summary

The vitamin A status of most newborn infants is marginal, and those who are born early and/or whose mothers have inadequate vitamin A intakes appear to be at particular risk. In many growing children, the reserves can maintain optimum amounts for no more than a few weeks. Colostrum and transitional milk are particularly rich in vitamin A to complement the low liver reserves of newborn infants. The vitamin A concentration in breast milk during the first two weeks of lactation is nearly double that at one month. Preterm milk is even higher in vitamin A concentration than term milk during the first several months, which is significant considering the particularly low vitamin A liver reserves of most preterm infants. Although vitamin A concentration in human milk depends on the mother's status, deficiency is rare among breast-fed infants, even in parts of the world where the deficiency is endemic. The protective effect appears to continue after breast-feeding is discontinued, presumably because some of the vitamin A provided by human milk is stored in the infant's liver.

The average daily dietary intake of vitamin A by unsupplemented lactating women in developing countries is less than half that of women in developed countries but still above the basal requirement recommended by the FAD/WHO. The average serum levels of retinol and RBP in unsupplemented lactating women from developing countries are approximately 70% of those in unsupplemented lactating women in developed countries. Yet, despite these large differences, the levels are in the adequate range.

Related to the differences in maternal vitamin A status, there are considerable differences in the vitamin A activity (retinol plus §-carotene) of the milk of unsupplemented mothers in developed and developing countries. Under conditions of relatively good maternal health and nutrition status in developed countries, mature human milk alone provides considerably more vitamin A than necessary to allow liver storage for at least the first six months of life, and probably for at least the first year; however, due to the lack of data on the vitamin A content of human milk in developed countries after six months postpartum, this cannot be known with certainty. Even in presumably more poorly nourished populations in developing countries, human milk alone provides sufficient vitamin A activity to prevent clinical deficiency throughout the first 12 months of life. However, the average amount in human milk in developing countries is not sufficient to allow liver storage after about six months of lactation, even when both retinol and carotene are counted. These are only averages; some low-income populations may provide insufficient vitamin A to the infant in breast milk earlier than that time, and other populations later. Breast milk continues to be one of the most important sources of vitamin A in the infant's diet in developing countries throughout the second year.

Despite the relatively lower levels in the milk of mothers from developing countries, breast milk is still the major source of vitamin A in the diets of their infants and young children. Thus, it is important to improve maternal status to increase the vitamin A content of their milk. Lactating women suspected of having low stores and/or those unable or unwilling to increase their dietary intake of the vitamin would be expected to benefit from supplementation. Since the concentration in human milk is dependent on maternal vitamin A status, their infants would also be expected to benefit, and potential toxicity from high-dose supplements given directly to the infant could be avoided.

Improving the vitamin A status of lactating women, promoting the use of colostrum, encouraging exclusive breast-feeding for four to six months of life, and adding appropriate vitamin A-rich weaning foods after that time while breast-feeding continues are important strategies for improving the vitamin A status of infants and young children. Because of the precarious vitamin A status of preterm and small-for-gestational-age infants, their mothers should receive particular support to enable them to provide their own milk to their infants. Breast-feeding throughout the first two years of life, with the addition of vitamin A-rich foods to the diet by six months of life, is particularly important in developing countries where vitamin A deficiency is a recognized public health problem. Health care workers, traditional birth attendants, community leaders, and the public need to be educated about this information so that breast-feeding will be promoted.

Acknowledgement

This study was completed under cooperative agreement DAN-5117-A-00-90994)0, United States Agency for International Development, Office of Nutrition.

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Manuals from the International Nutrition Foundation for Developing Countries

Rapid assessment procedures to improve the household management of diarrhea. Elizabeth Herman and Margaret Bentley. INFDC, Boston, Mass., USA, 1993. (ISBN 09635522-3-6) 86 pages, paperback.

This manual gives guidance on how to rapidly collect, analyse, and use information about the cultural context of diarrhoea. Its purpose is to make it possible to identify household and behavioural factors that are characteristic of a local culture and to facilitate the development, implementation, and monitoring of programmes for the control and prevention of diarrhoea. Rapid assessment procedures (RAP) are used to determine people's beliefs about how the body works, the causes and consequences of illness, and other factors that influence the household response to diarrhoea. Separate sections present the RAP methods, information for diarrhoea case management, a field guide for conducting a study, and options for applying the study results.

A manual for the use of focus groups. Susan Dawson, Lenore Manderson, and Veronica L. Tallo. INFDC, Boston, Mass., USA, 1993. (ISBN 0-9635522-2-8) 96 pages, paperback.

This is a practical, step-by-step guide to the use of focus groups, a research approach that has proved extremely useful in a wide variety of settings for providing information rapidly and economically on the range of opinions, knowledge, beliefs, and practices of a population. Focus groups are organized interview sessions with specific goals, structures, time frames, and procedures and have become recognized by the scientific community as a valuable tool for gaining information for a variety of purposes. This manual was written to help researchers in the social and health sciences to use focus groups to learn more about social and cultural issues influencing health behaviour and the prevention and control of disease. Even those familiar with focus-group research will find that it provides new insights and examples that can be adapted to different research questions and teaching contexts.

Both of these books are available from the International Nutrition Foundation for Developing Countries, P.O. Box 500, Boston, MA 021140500, USA. For citizens of industrialized countries and the staff of international organizations, the price per book is US$10, plus $2 postage and handling (add $0.50 for each additional copy). For citizens of developing countries, it is US$5, plus $3 per book for postage and handling by surface mail ($4 for air mail).

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