Evaluation of the fortification of sugar with vitamin A

Abstract

Background, motivation and hypothesis: A high prevalence of micronutrient deficiencies has been described in the South African black population, especially vitamin A deficiency and iron deficiency anaemia (IDA). However, iron overload is also a problem in South African blacks. The literature indicated that while there is a high prevalence of IDA in especially young African girls, there is also an increased susceptibility to iron overload - probably not only of increased intakes by men of beer brewed in iron containers, but also because of a genetic factor. It seems that in South African blacks, the prevalence of the homozygous state for haemochromatosis may be more than ten times higher than in European populations. The role of vitamin A in iron metabolism has received increased attention during recent years. Studies have shown that vitamin A has protective effects during iron supplementation such as an increased mobilisation of iron. It would thus be of benefit for prevention and intervention programmes to know if vitamin A fortification/supplementation would improve iron status in vulnerable groups at lower, safer levels of iron supplementation/fortification. The emergence of chronic diseases of lifestyle in Africans in transition (urbanisation), especially obesity and stroke, is causing a double burden of disease. One of the consequences of obesity is raised plasma fibrinogen levels, which is a risk factor for stroke and coronary heart disease. Stroke is known to be the first chronic disease of lifestyle to emerge in the South African black population during urbanisation and is thought to be related to high incidences of hypertension and hyperfibrinogenaemia in this population. Epidemiological studies indicated that vitamin A intake and status are associated with plasma fibrinogen levels. The hypothesis developed for this study, is that increased vitamin A intake through consumption of vitamin A fortified sugar will improve iron status and decrease plasma fibrinogen levels of a group of black South African women. This hypothesis is based on the evidence that there is an interaction between vitamin A and iron absorption, transport and function, a possible interaction between plasma fibrinogen and vitamin A status, and therefore also a possible relationship between iron status and fibrinogen. The major objective of this project was therefore to prove that iron deficiency can be addressed by increasing vitamin A status of young black South African women. If this is true it could mean that lower levels of iron fortification or supplementation may be necessary to address iron deficiency problems, without increasing the risk of an iron overload when genetically susceptible individuals consume iron fortified products. Another objective was to determine the effect of vitamin A supplementation on the fibrinogen levels in the same sample. Methods: To test the hypothesis , the study was designed in different phases: Phase 1 : In this phase, the suitability of the habit of tea drinking as a vehicle for fortification by determining the amount of tea consumed , the type of tea mostly consumed, milk and sugar additions, when tea is consumed, the reasons for tea consumption and whether people like tea, were examined. Phase 2 : During phase 2, the fortification levels and fortifying the sugar, as well as compliance and consumer acceptability of the vitamin A fortified sugar, were determined. Phase 3 : In phase 3 the effects of vitamin A fortified sugar on iron status and fibrinogen levels by means of a double blind , placebo controlled parallel study in 13-25 year old black South African, non-pregnant, non-lactating, apparently healthy female volunteers (n= 100) were tested. Measurements were taken twice at baseline and thereafter during weeks 4, 8 and 12. Variables measured included: Anthropometry (Body mass index (BMI) , waist-to-hip ratio) Serum retinal (High performance liquid chromatography - HPLC) Haemoglobin (Cyanmethaemoglobin-colorimetry)

Haematocrit (Numeric integration) Mean cell volume (Impulse generating) Red blood cell and white blood cell count (Cell counting - autoanalyser) Serum iron (Colorimetry) Serum ferritin and transferrin (Immunoturbidity) Full blood count (Coulter counter) Fibrinogen (Modified Clauss method) Results: In phase 1 it was found in a sample of 500 subjects that at least one cup of tea was consumed by the 92,9 % of the participants in this study, with rooibos tea selected as the most popular (50 % of tea consumed). Sugar was chosen by 40,4 % and milk by 37,0 % of the sample to be the preferential ingredient added to tea. According to the preference scales of these respondents, tea was the third most consumed beverage in summer and the first most consumed beverage in winter. Phase 2 indicated that sugar fortified with vitamin A seemed to be acceptable, as no differences in the colour and taste of the fortified sugar were noted. A statistically significant difference was, however, noted in the smell of the sugar that was fortified to a level of 100 % of the recommended daily allowance of the sample population. Compliance to the intake of the fortified sugar was good as 93 % of the participants in this study used white sugar on a daily basis. This may indicate that sugar is a suitable vehicle for vitamin A fortification. The main results of phase 3 indicated that vitamin A intakes influenced serum iron, but not to the extent that it could rectify iron deficiency at the levels of iron consumption of these subjects. It further showed significant correlations between serum retinal and iron status variables in this homogeneous group of subjects, confirming a relationship between vitamin A and iron status. This intervention study provides some evidence that increased intakes of vitamin A by subjects with acceptable vitamin A status, resulted in small, but statistically significant decreases in plasma fibrinogen. These decreases were, however, not sustained, probably because of observed increases in BMI and weight. Conclusions: From the results of this study, the following conclusions can be drawn: • In a random sample (n = 100) of 13-25 year old black South African girls and women, 12 % had an unacceptable low vitamin A status (serum vitamin A ~ 30 μg/dL) and 58 % had low iron status (based on a variety of iron status variables). Clearly, micronutrient deficiencies are prevalent in these urban women who follow a western-type of diet. • Compliance to the intake of the fortified sugar was good and this indicates that sugar is a suitable vehicle for vitamin A fortification. • Although dietary intake of vitamin A fortified sugar did not result in clinical improvements of iron status variables, statistically significant changes were observed in serum iron and the results thus suggest that the additional vitamin A consumed influenced iron metabolism. The significant correlations observed between serum retinal and iron status variables in this homogeneous group of subjects, confirm a relationship between vitamin A and iron status. • There is some evidence that increased intakes of vitamin A by subjects with acceptable vitamin A status, resulted in small, but statistically significant decreases in plasma fibrinogen. These decreases were, however, not sustained, probably because of observed increases in BMI and weight. Recommendations: For practical implications, the results of this project may impact on public health policy regarding the treatment of micronutrient (specifically vitamin A and iron) deficiencies. Programmes aimed at the prevention of micronutrient deficiencies, rather than treatment, may help to prevent the rising health costs in this country. The results of this study indicate that further research is needed addressing the following issues:

• The mechanism by which vitamin A and iron interact need to be studied in order to plan future intervention programmes. • Optimal fortification levels need to be determined through more research in order to identify safe iron and vitamin A levels, which will rectify deficiency problems without increasing risk of haemochromatosis in Africans. • Cost-effective analysis should be done to determine the most cost-effective interventions for the situation in South African rural, urban and poorest rural areas. A mix of strategies would probably be needed to ensure adequate vitamin A and iron intakes for all people. • The results of this study regarding the high prevalence of especially iron deficiency in young , black women, as well as the possibility that sugar could be a fortification vehicle should be communicated to policy makers in the South African Department of Health (Directorate Nutrition) and should be used in nutrition education of the public.