Assessment ot trace element content in the foodstuffs commonly consumed in selected parts of Rift Valley in Kenya

Abstract

This study was carried out to determine the trace heavy metals found in common vegetables, cereal crops and medicinal plants which are locally available and consumed in selected parts of southern region of Rift Valley province in Kenya. Sampling sites covered four districts in this region which included Kericho, Buret, Bomet and Nakuru. Samples of five varieties of vegetables, three varieties of cereals and ten varieties of medicinal plants used for anti-acidity treatments were obtained from local farms in different areas of the region and analyzed for iron (Fe), copper (Cu), manganese (Mn), and zinc (Zn) by X-ray Fluorescence Spectroscopy method. Prepared staple foods of porridge, ugali, beans and vegetables were analyzed for bioavailability of the trace heavy metals.

The average iron content in the cereals was 374 ug/g for beans, 245 Jlg/g for wimbi and 172 ug/g for maize. The concentration of iron ranged between 247-813 ug/g in beans, 124-326 ug/g in maize and 169-401Jlglg in wimbi. The average manganese content in wimbi, beans and maize were 200, 47.8 and 24.8 Jlglg respectively, while the range varied as follows; 79-339 ug/g in wimbi, 19.2-119 ug/g in beans and 17.9-36.2 ug/g in maize.

Beans had the highest zinc content of 46.0 Jlglg and ranged between 29.1-63.4 Jlglg. The mean zinc content in maize and wimbi were 33.4 and 21.1 Jlglg respectively. The range of zinc in maize was 15.4-60.1 ug/g while that in wimbi ranged between 14.8-34.1 ug/g. The mean copper content in maize, wimbi and beans were 11.4, 15.2 and 22.4 ug/g respectively. Copper content was in the range of values <10.0-12.4 in maize, <10.0-18.4 in wimbi and <10.0-30.2 ug/g in beans.

In vegetables, mean iron concentration in black nightshades, spider plant, pumpkin leaves. vine spinach and kales were 5,920, 4,030, 3,314, 1,418 and 730 ug/g respectively. Manganese in spider plant and kales averaged 547 and 157 ug/g respectively. Vine spinach, black nightshades and pumpkin leaves had average manganese content of 539,440 and 442 ug/g respectively. The average zinc concentrations (ug/g) were 219 in spider plant, 121 in pumpkin leaves, 119 in black nightshades, 115 in vine spinach, and 84.6 in kales. Minimum and maximum mean copper contents were observed in kales (13.0 ug/g) and spider plant (2l.9 ug/g). Copper content in black nightshades, pumpkin leaves and vine spinach averaged 18.4, 16.9 and 12.4 ug/g respectively.

Porridge, ugali and beans were analyzed for bioavailable iron, manganese. copper and zinc. The average bioavailability for these elements ranged between l.6-24.7% for iron; l.0-1O.6% for manganese; 6-22.9% for copper and 1.0-11.8% for zinc. Similarly, four vegetable types (vine spinach, spider plant, black nightshade and pumpkin leaves) were analyzed for bioavailability of the same elements. Their average-bioavailability ranged between 0.2-6.0% for iron; 0.3-3.4% for manganese; 5.4-16.9% for copper and 0.7-7.8% for zinc,

Ten indigenous medicinal plants samples commonly used for anti-acidity treatments were investigated as potential sources of trace elements, The medicinal plant samples were analyzed for calcium, copper, iron, manganese, potassium and zinc, Calculated on the basis of dry weight, thetrace element concentrations ranged between 6,795 to 19,350 Ilg/g for calcium; 14.1 to 25.6 ug/g for copper; 1,163 to 6,360 Ilg/g for iron; 104 to 13,850 ug/g for manganese; 29,150 to 53,400 Ilg/g for potassium, and 21.2 to 53.0 ug/g forzinc.