Determination of micronutrients, heavy metals and Proximate analysis of selected indigenous vegetables in Kirinyaga East Sub-County, Kirinyaga County

Abstract

Socio-economic changes that have taken place in Africa have influenced peoples eating habits in both rural and urban set-ups. Indigenous vegetables are important for food insecurity, malnutrition reduction and therapeutics in sub-Saharan African countries. In Kirinyaga County, indigenous vegetables are underutilized or neglected due to some nutritional content are known and others unknown. Limited data exist on the precise levels of key micronutrients (e.g. iron, zinc, magnesium) in specific indigenous vegetables cultivated in Kirinyaga East Sub-County. Variability in nutrient content due to farming practices, soil types, and climatic conditions in the region has not been comprehensively studied. Leaves are the most preferred parts of indigenous vegetables for consumption. Although they have nutritional benefits, there is a need to determine the safety levels due to toxic metals in vegetables contaminated with pesticides, heavy metals and toxins leading to failure of certain organs of the human body. The study aimed to determine levels of micronutrients (calcium, iron, magnesium and zinc), heavy metals (lead and cadmium) using AAS (atomic absorption spectrometer) using and proximate analysis (ash content, moisture content, crude fat, protein content, carbohydrates and crude fiber) of selected African indigenous vegetables (African nightshade, Spider plant, Vine spinach and Pumpkin leaves) in Kirinyaga east sub county. The results revealed that African indigenous vegetables are rich in essential micronutrients. Pumpkin leaves had the highest calcium levels (14,070.81 mg/kg), spider plant showed the highest iron concentration (233.53 mg/kg), African nightshade recorded the highest zinc content (483.33 mg/kg), while vine spinach was richest in magnesium (570.87 mg/kg). Proximate analysis indicated that spider plant and African nightshade contained higher protein levels (up to 17.9%), while moisture content ranged from 82–91%. Crude fat levels were consistently low, confirming African indigenous vegetables as nutrient-dense but energy-light vegetables Cadmium and lead concentrations varied across species and locations, with African nightshade and vine spinach showing relatively higher levels. However, all values remained within WHO/FAO permissible limits, indicating that the vegetables are safe for human consumption in terms of heavy metal contamination. African indigenous vegetables have high nutritional potential and can be promoted as affordable dietary sources of essential minerals and protein to combat malnutrition.