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Health and nutrition

Dietary approaches to the prevention of vitamin A deficiency

Dietary approaches to the prevention of vitamin A deficiency

Somsri Charoenkiatkul, Aree Valyasevi, and Kraisid Tontisirin, Institute of Nutrition, Mahidol University, Faculty of Medicine, Ramathibodi Hospital, Bangkok, Thailand

In Thailand, one of the major nutritional problems is vitamin A deficiency, especially among pre-school children residing in rural areas of the north-eastern and northern regions. Twenty-five years ago the Interdepartmental Committee on Nutrition for National Defense (ICNND) survey [7] found inadequate intakes of vitamin A and reported that vitamin A malnutrition existed in the northern and north-eastern regions of Thailand, particular!' in infants and small children, the problem remains unresolved today.

A recent survey of the dietary nutrient intake of pre-school children residing in Ubon Province, north-eastern Thailand [4] revealed a low energy intake (about 80 per cent of the requirement for their ages) The energy content derived from fat constituted only 3 to 6 per cent of the total energy intake. Average vitamin A intakes were only 63 µg retinal equivalents per day for children two years of age, 252.6 µg retinol equivalents for those four years of age, and 326.4 µg retinol equivalents for those six years of age. These intakes are markedly lower than the dietary allowances recommended by WHO in 1974 [6]. The average dietary nutrient intake per person per day for pre-school children is shown in table 1.

Serum vitamin A levels have also been studied recently in the pre-school children, schoolchildren, and lactating mothers of Ubon Province [4]. The results are shown in table 2, which indicates that vitamin A deficiency is a public health problem in pre-school and schoolchildren in rural north-eastern Thailand. In this survey, vitamin A levels of less than 10 ?g/ml were found to have a prevalence of 17 per cent; according to WHO criteria, vitamin A deficiency is a public health problem if the prevalence figure is over 5 per cent among pre-school children. The findings for schoolchildren were similar. Forty-two per cent of lactating mothers were marginal, and since their infants depended almost completely on mothers' milk, it is likely that the vitamin A status of these infants was also marginal.

It was the purpose of the present study to determine whether solutions to the problem of vitamin A deficiency should focus on increasing the dietary intake of provitamin A (ßcarotenes), which is present in vegetables which are already available locally or which can be introduced into rural northern and north-eastern Thailand.

POTENTIAL SOURCES OF VITAMIN A IN LOCAL VEGETABLES AND FRUITS

Provitamin A (ß-carotenes) is widely distributed among plant foods, chiefly dark-green leafy vegetables, such as swamp cabbage, ivygourd, kale, spinach, and amaranth. Other sources include yellow and red fruits, such as pumpkin, ripe papaya, carrot, and ripe mango [2].

TABLE 1. Average Dietary Nutrient Intake per Person per Day in Preschool Children (Posse, Ubon, North-east Thailand, 1973) [4]

a. Food and Nutrition Board, Recommended Dietary Allowances, 8th rev. ed. (National Academy of Sciences, Washington, D.C., 1974).

TABLE 2. Serum Vitamin A Levels in Pre-school Children, Schoolchildren, and Lactating Mothers (Ubon, North-east Thailand, 1974 and 1978) [4]

TABLE 3. The Nutrient Composition of Ivygourd, Kale, Chinese Swamp Cabbage, Pumpkin and Papaya (Mean ± SEM)

a. From FAO and US Department of Health, Education and Welfare, Food Composition Table for Use in East Asia (December 1972).

Most of the vegetables and fruits mentioned above are available locally or can be widely promoted in rural communities; we therefore decided to determine the ß-carotene content of certain fruits and vegetables. The vitamin A, protein, and fat contents of some green leafy vegetables and of pumpkin and papaya are shown in table 3. No significant differences in ß-carotene (or retinol equivalent) content were found for ivygourd, kale, and Chinese swamp cabbage, but ß-carotene was significantly higher in all of these than in pumpkin and papaya (P<.001). We therefore evaluated the effects of supplementation with one of the green leafy vegetables - ivygourd -on serum carotene and vitamin A levels of pre-school children.

EXPERIMENTAL DESIGN

The amounts of these foods needed to provide about 250 ?g and 400 ?g retinol equivalents were calculated so that they could be used as guidelines for daily supplementation; these figures correspond to allowances recommended for preschool children by the FAD/WHO and the RDA (US recommended dietary allowances) respectively (table 4).

The Effects of Supplementation with Green Leafy Vegetables

The study sample consisted of two groups, numbering 15 pre-school children each, whose usual diets averaged approximately 560 ?g retinal equivalents. Both groups of subjects had been in an orphanage for more than six months; most of the children had been sent to the orphanage from hospitals. Their diet consisted of a rice base. The two groups of subjects were matched for sex, weight, height, and nutritional status.

Group 1 subjects were tested during the wet season from late May to early October and group 2 subjects during the cool, dry season from late October to early January. Subjects in group 1 were given no supplement for a period of two weeks and then received daily supplements of cooked ivygourd containing 1,081 + 12 µg ß-carotene or 180 µg retinol equivalents. This portion accounted for 72 per cent of the daily requirement of vitamin A recommended by the FAO/WHO in 1974 [6]. Subjects in group 2 received 1,187 + 10 µg ß-carotene or 198 µg retinol equivalents in cooked ivygourd daily for two weeks, accounting for 79 per cent of their daily vitamin A requirement; they then received daily multi-vitamin mixtures providing 450 µg retinol equivalents for two weeks.

A fasting blood sample was taken from each child by venipuncture one day before and after each two-week period. Hematocrit was measured by micromethod [1]. Serum ß-carotene and vitamin A were determined within two weeks by Neeld and Pearson's method [11], using sigma grade all-trans ß-carotene and purified crystalline retinyl acetate as standards. The serum was also determined for total retinol binding protein (RBP) by radial immuno diffusion [10] and albumin by modification of Doumas's method [5, 9] .

The results for group 1 are shown in table 5. Significant increases (P<.01) in serum 0-carotene and vitamin A levels. as well as total RBP (P<.05) were found after the second period. These findings indicate that ß- carotene was not only absorbed adequately but also converted to vitamin A effectively.

TABLE 4. The Amounts of Ivygourd, Kale, Chinese Swamp Cabbage, Pumpkin and Papaya^a Providing about 250 ?g and 400 ?g Retinol Equivalents (RE), the Allowance Recommended for Pre-school Children by the FAO/WHO^b and the US RDA^c

a. Calculated from table 3.
b. FAD/WHO Monograph Series 61 (WHO. Geneva, 1974)
c. Food and Nutrition Board, Recommended Dietary Allowances, 9th ed. (National Academy of Sciences, Washington, D.C., 1980).

The results for group 2 are shown in table 6. A significant increase (P<.001) in serum ß-carotene was demonstrated after the ivygourd supplementation, but no differences in serum vitamin A and total RBP were found. After the multivitamin supplementation, an increase in serum vitamin A (P<.001) as well as in total RBP (P<.01) was demonstrated.

The drops in ß-carotene, vitamin A levels, and total RBP shown in table 5 for group 1 after the control period when no supplement was given is the result of the discontinuation, once the study began, of the multi-vitamin supplement that was being administered to the children.

Increases in ß-carotene after ivygourd supplementation were observed in group 2 as well as in group 1. No differences in serum vitamin A and total RBP were found in group 2 subjects after the vegetable supplementation, in contrast to a marked increase of both indices in group I subjects. The lack of change in vitamin A levels in group 2 subjects (shown in table 6) after the period of supplementation with ivygourd reflects the dicontinuation of multi-vitamin supplements at the start of the intervention. The rise in ß-carotene level is the result of the active carotenoids in ivygourd.

The drop in ß-carotene during the period of supplementation with multi-vitamins (table 6) was probably due primarily to the decrease in ß-carotene intake, but may have been further influenced by the higher rate of infections and poorer appetite in group 2 subjects, 40 per cent of whom had developed upper respiratory tract infections, diarrhoea, and poor appetite during the study; the overall prevalence of these disorders in group 1 was 24 per cent. Moreover, a longer period of infection was noted in group 2 subjects. Due to these infections the absorption of ß-carotene may have been less efficient and urinary excretion of this substance probably increased [8,14].

TABLE 5. Biochemical Data of Subjects in Group 1 (Mean±SEM, n=15)

a= P<.001, b= P<.0.1, c= P<.05.

TABLE 6. Biochemical Data of Subjects in Group 2 (Mean ± SEM, n=15)

a= P<.0.5. b= P<.001, c= P< 0 1.

APPROACHES TO THE PREVENTION OF VITAMIN A DEFICIENCY

The present study confirms previous studies in India and elsewhere [5, 9, 10] that 9-carotene in various green vegetables can be adequately absorbed and also converted to vitamin A effectively. The green leafy vegetables were acceptable to these subjects; only 2 of 30 children (6.7 per cent) would not eat them. Therefore, with effective nutritional education and the promotion of home gardening, mothers will be able adequately to supplement their children's diets with green leafy vegetables.

Observations from this study indicated that under conditions such as those of protein-energy malnutrition (PEM) with recurrent infections, the serum vitamin A levels of some children may drop despite daily supplementation with vegetables with high provitamin A content, and may decrease markedly during a period of no supplementation. The interaction of PEM and infection may cause a defect in vitamin A metabolism, particularly the transportation, utilization and storage of vitamin A, and lead to a decrease in serum vitamin A. However, by encouraging the consumption of green leafy vegetables, vitamin A status can be improved satisfactorily.

Reducing the level of infection will increase the benefit derived from an additional ß-carotene or vitamin A intake. Improving protein intake may also be of value in this respect. Therefore a long-term approach to the prevention of vitamin A deficiency should be linked to efforts to improve general nutritional status. Since nutritional improvement is one major component of primary health care (PHC), the attempt to raise vitamin A nutritional status should form part of a broader compaign to promote better general health and sanitation.

Effective nutrition education is essential for transmitting information, changing attitudes, and eventually altering feeding and eating behaviour. Once community members are convinced of the importance of better nutrition, home and village gardening can probably be promoted with more success.

Operational research is needed to establish an effective model for improving vitamin A nutritional status within the PHC context.

REFERENCES

1. G. E. Cartwright, Diagnostic Laboratory Hematology (Cyrunne & Stratton, New York, 1968), p. 103.

2. S. Charoenkiatkul, "Role of Green Leafy Vegetables in Prevention of Vitamin A Deficiency in Thai Children," M.Sc. thesis (Mahidol University, Bangkok, Thailand, 1982).

3. R. P. Devadas and N. M. Murthy, "Biological Utilization of ß-carotene from Amaranth and Leaf Protein in Pre-School Children," Wld. Rev. Nutr. Diet, 31: 159 - 161 (1978).

4. S. Dhanamitta, B. Stoecker and A. Valyasevi, "Community Approaches to Prevention of Vitamin A Deficiency," paper presented at the IVACG Meeting, Jakarta, Indonesia, 11 - 13 October 1980.

5. B. T. Doumas, W. A. Watson and H. G. Biggs, "Albumin Standard and the Measurement of Serum Albumin with Bromcresol Green," Clin. Chim. Acta, 31: 87 (1971).

6. FAD/WHO, Monograph Series, No. 61 (WHO, Geneva, 1974).

7. Interdepartmental Committee on Nutrition for National Defense, The Kingdom of Thailand, Nutrition Survey, October - December 1960 (Department of Defense, Washington, D.C., 1962).

8. R.V. Lala and V. Reddy, "Absorption of ß-Carotene from Green Leafy Vegetables in Undernourished Children," A.J.C,N. 23: 110 - 113 (1970).

9. P. H. Lolekha and W. Charoenpol, "Improved Automated Method for Determining Serum Albumin with Bromcresol Green," Clin. Chim., 120(5): 617 - 619 (1974).

10. G. Mancini, A. O. Carbonara and J. F. Hereman, "Immuno-chemical Quantitation of Antigens by Single Radial Immuno-diffusion," Immunochem., 2: 235 (1965).

11. J. Neeld and W. Pearson, "Macro. and Micro-Methods for the Determination of Serum ß-Carotene and Vitamin A Using Trifluoroacetic Acid," J. Nutr., 79: 454 - 462 (1963).

12. S. M. Pereira and A. Begum, "Studies in the Prevention of Vitamin A Deficiency, Part 1," Ind J. Med. Res., 5613): 362 369 (1968).

13. N. C. Rao and N. B. S. Rao, "Absorption of Dietary Carotenes in Human Subjects," A.J.C.N., 23: 105 - 109 (1970).

14. S. G. Srikantia, "Human Vitamin A Deficiency," Wld. Rev. Nutr. Diet, 20: 184 (1975).

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