Thesis: The Degree of Doctor of Philosophy
Vitamin A Deficiency (VAD) continues to be a public health problem in low income
countries including Tanzania. It affects the vulnerable social groups namely women of
reproductive age (15-45 years) including pregnant women and lactating mothers; and
children below five years. Despite the Government’s efforts to eliminate VAD among the
lactating mothers and children below five years, the prevalence is still very high. Vitamin
A deficiency in Tanzania accounts for approximately one-third in children below five
years, 39% of pregnant women and 35% for lactating mothers. The main underlying
cause of VAD is a diet that is chronically insufficient in vitamin A. One intervention to
eliminate vitamin A deficiency in this study was fortification of virgin sunflower oil with
vitamin A. Despite the fact that utilization of the fortified cooking oil with vitamin A at
household level is increasing rapidly in Tanzania, there is little information on the use of
fortified cooking oil with vitamin A as the major source for preventing VAD. Therefore,
the present study was designed to fill the gap by evaluating the effectiveness of fortifying
virgin sunflower oil with vitamin A on the retinol status of children below five years and
lactating mothers in Manyara and Shinyanga regions of Tanzania. Each region involved
three intervention districts and one control district. Intervention districts were involved in
consumption of fortified virgin sunflower oil with vitamin A in the households. The
fortification level of vitamin A in the sunflower oil was 30-40 mg/kg as per East African
Standards recommendation. No control was made on the amount of oil to be used in the
preparation of any meal in the household. Intervention districts were encouraged to buy
fortified sunflower oil from the specified shops where the fortified oil was sold at
subsidized rate of 2100 Tshs per liter and use it for preparing food. For mothers who were
not able to liters (1 L, 3 L, 5 L and 20 L container) there was fortified sunflower oil with
vitamin A sold in small quantities known as coops. Through socio-marketing, this group was also encouraged to consume vitamin A rich foods and diversify their diets. During
intervention period the control groups were not receiving sunflower oil fortified with
vitamin A. Instead, they were encouraged to use unfortified sunflower oil for cooking and
consume vitamin A rich foods as well as diversifying their diets. During intervention
period, mothers were visited at their households by the village health workers and home-
based care providers once every week to monitor compliance to the use of the fortified
oil. They were encouraged to buy the fortified sunflower oil and use it for food
preparation. Control groups started receiving the fortified sunflower oil after the
intervention period of 18 months. Assessment of consumption of fortified sunflower oil
with vitamin A was carried out in the intervention districts where fortified virgin
sunflower oil with vitamin A in the households was practiced. A total of 569 mother-child
pair was involved to evaluate the potential use of the fortified virgin sunflower oil in
controlling vitamin A deficiency. Retinol in the Dry Blood Samples was determined by
Retinol Binding Protein enzyme linked immune assay (ELISA) method while Retinol in
the oil was determined by HPLC method. Results revealed that, at baseline about 60%
(n=313) of the oil samples from the households had retinol concentration level below 20
mg/kg, out of which majority were from Manyara (n=245, 47%) and only few samples
(n=68, 13%) were from Shinyanga. At end-line, majority of households oil samples
(89.9%, n=471 of the) had retinol concentration of 20-40 mg/kg, which these values were
within the recommendation by East African Standards EAS 269:2017 (TZS 1313:2014)
fortified edible oils and fats specification. Baseline mean serum retinol concentrations of
the children and lactating mothers in the control districts were 14.63±5.31 and 20.75±7.32
μg/ml, respectively, while in the intervention districts, the mean serum retinol
concentrations for the children and lactating mothers were 15.14±5.44 and 20.10 ±7.33
μg/ml, respectively. These values were lower than those recommended by World Health
Organization which defines the plasma retinol concentrations of <0.7 μmol/L or <17.325 μg/ml of Retinol Binding Protein for the children and plasma retinol concentrations of
<1.05 μmol/L or <26.04 μg/ml of Retinol Binding Protein for the lactating mothers as
vitamin A deficiency. End-line mean serum retinol concentrations in the control districts
were 14.83 ±5.95 μg/ml, for the children and 21.35±7.87 μg/ml for the lactating mothers,
while in the intervention districts mean serum retinol concentrations were 17.59±10.20
μg/ml for the children below five years and 22.83±9.48 μg/ml for the lactating mothers. A
quasi-experimental non-equivalent control group design with intention to treat vitamin A
deficiency showed that, fortified virgin sunflower oil with vitamin A in children below
five years and lactating mothers had positive effects on retinol serum concentration. Also
fortified virgin sunflower oil with vitamin A had positive effects on anthropometric status
namely, weight for age, height for age and weight for height Z-scores. Children who
consumed fortified sunflower oil with vitamin A progressively improved in weight for
age from -0.81 to -0.72 SD, height for age -1.36 to -0.81 SD and weight for height -0.21
to -0.06 SD Z-scores (baseline vs. end-line). In the control districts weight for age was -
1.08 to -0.93 SD, height for age -1.61 to -1.28 SD and weight for height -0.25 to -0.16 SD
Z-scores (baseline vs. end-line). Beside fortified oil, other factors which may account for
improved serum retinol concentration and anthropometric status of the children and
lactating mothers included vitamin A mega doses supplement (children), dietary diversity
and maternal knowledge about consumption of vitamin A rich foods and age
(breastfeeding and non-breastfeeding). Also, despite significant decrease in vitamin A
levels in the fortified virgin sunflower oil during six months of storage (11%) and in the
scooping study (10%) and the slight increase in the quality aspects namely peroxide;
anisidine, malondialdehyde and Totox values, the oil was still good for healthy. The
major socio-economic and demographic factor which significantly (<0.05) influenced
vitamin A status of these socio groups is residence. Living in rural areas decreased like
hood to diversify foods compared to urban area. Also seasonal vitamin A rich foods mainly plant based foods is a great problem in rural areas compared to urban areas.
Therefore, to address vitamin A deficiency problem; the use of fortified cooking oils with
vitamin A; increasing consumption of vitamin A rich foods and dietary diversification
should be encouraged to sustain the prevention and control of this deficiency.