Trace Element Analysis in Infant Food from Selected Rural-Urban Areas using TXRF Technique

Inadequate intake of dietary trace elements during infancy has a direct impact on the lifelong health of a person. It causes delayed sexual maturation, poor growth, faulty immune functioning, tooth decay and altered hormonal function. These effects are irreversible and may lead to poor school performance, reduced work competence and decreased productivity later in life.

Complementary feeding is recommended after six months of exclusive breastfeeding. These foods should adequately provide all the nutrients as the infant continues to breastfeed up to two years or more. In most rural and urban settings, the first complementary food given to an infant is usually a modification of the family’s staple food, which more often, is usually in form of porridge. The porridge flour is initially prepared from cereals such as millet, maize, wheat, rice or sorghum with addition of milk and sometimes sugar or honey, if available. Once the infant is able to take the cereal porridge well, porridge made from a mixture of cereals, pulses and vegetables can then be given to the infant. Therefore, it is important to know the suitability of these complementary infant foods.

The aim of this study was to determine the trace elements in infant food from selected rural-urban areas. Ninety samples were collected from selected rural-urban areas. These areas included: Kirwara, Bomet, Mitaboni, Turbo, Sega, Nairobi, Kericho, Kisumu, Eldoret and Thika. The selection of these areas was based on the proximity of rural areas to the urban areas. The samples were digested using nitric acid in an open system. The trace element content was then determined using Total Reflection X-Ray Fluorescence technique. The analytical method was validated using a certified reference material of milk powder (New GBW 10017) from LGC. At 95% confidence level, there was no significant difference between the certified values and experimental values for the trace elements Fe, Zn, Cr, Mn and Cu. This analytical method was therefore suitable for determining trace element of the infant food.

Trace element concentrations of Fe, Zn, Cu and Mn were found to be very low in the maize flour porridge.  Zinc varied from 14.3 ± 0.3 to 17.2 ± 0.3 mg kg-1; Fe varied from 14.6 ± 1.6 to 17.7 ± 1.0 mg kg-1; Cu varied from 0.72 ± 0.02 to 0.95 ± 0.02 mg kg-1; and Mn varied from 1.96 ± 0.39 to 2.49 ± 0.28 mg kg-1. Both Cr and Ni concentrations were below detection limits. Porridge flour that contained millet, as the main ingredient, had the highest concentrations of Mn ranging from 86.5 ± 0.6 to 165 ± 5 mg kg-1.  Samples, especially those which had legumes such as soya and groundnuts as one of the ingredients, had iron levels above 100 mg kg-1. Concentrations of Pb ranging from 0.12 ± 0.04 to 0.84 ± 0.16 mg kg-1 were found in approximately 31 % of the samples, with highest percentage of these samples coming from either diesel milled flour or flour that contained fish powder.

The results indicate that children who are fed only on maize based complementary foods are more likely to be deficient of trace elements since the samples had relatively low levels of the essential elements. Complementary foods which had some legumes had relatively high levels of Zn and Fe. Given that 45% of zinc and 2% to 20% of Fe can be absorbed from the legume based foods, then these may be good source of Zn and Fe for infants.

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