Trace Element Concentrations in Some Traditional Diets Consumed in Selected Parts of Eastern Province of Kenya

Abstract

Dietary quality is vital in maintaining sound nutritional status. The ecological conditions thus influence the type of diets and their nutritional quality. The purpose of this study was to determine the trace element/mineral content of some of the commonly consumed diets in Machakos, Kitui, Makueni and Mwingi districts. Decorticated maize, beans and finger millet flour samples were purchased from the local markets. For each category, a total of ten samples were collected from each district. The samples were put in plastic bags, sealed and transported to the laboratory in the Institute of Nuclear Science & Technology, University of Nairobi for preparation and analysis. The cooking of the samples was carried out according to local traditional methods. In the decorticated samples, mean copper concentrations were observed to be below 20 μg·g -1 ; mean zinc concentrations ranged from 34 to 63 μg·g -1 and mean manganese concentrations were in a similar range of 34 to 78 μg·g -1 . The mean iron concentrations were significantly high with a range of 161 μg·g-1 to 287 μg·g -1 . A similar trend was observed in the beans where the mean copper concentrations varied from 11 to 33 μg·g -1 , mean zinc concentrations ranged from a low value of 24 μg·g -1 to a high value of 35 μg·g -1 , mean manganese concentrations varied from 33 μg·g -1 to 98 μg·g -1 and the mean iron concentrations ranged from 227 μg·g -1 to 647 μg·g -1 . The cooked Muthokoi samples from Machakos district had relatively high mean trace element concentrations: manganese—109 μg·g -1 ; iron—280 μg·g -1 ; copper—19 μg·g -1 ; and zinc—41 μg·g -1 . The only exception was mean iron concentrations which were extremely high in samples from Mwingi District where the concentrations varied from 73 μg·g -1 to 1597 μg·g -1 . In finger millet flour, the mean manganese concentrations varied from 95 to 290 μg·g -1 , whereas the mean iron concentrations ranged from 127 μg·g -1 to 259 μg·g -1 . In contrast, the mean copper and zinc concentrations were low in comparison to the manganese and iron concentrations. As a whole, the mean copper concentrations in the diets are significantly low compared to the other three trace elements. However, the total content is not necessarily a reflection of the amount assimilated in the body. Finger millet was found to be an excellent source of manganese and iron whereas beans were observed to be good sources of iron. All the food crops were observed to poor sources of copper.