Evaluation of Nutritional and Toxicological Significance of Essential Metals and Iodine in Vegetables and Spices from Kogi Metropolis,1 Nigeria

A study was conducted in Kogi Metropolis, Nigeria, to evaluate the levels of iodine and selected essential elements – calcium (Ca), magnesium (Mg), iron (Fe), and zinc (Zn) – across four widely consumed vegetables and spices, namely Amaranthus hybridus (smooth amaranth), Allium sativum (garlic), Lactuca sativa (garden lettuce), and Ocimum gratissimum (African basil). Iodine quantification was performed using UV–Visible spectrophotometry, while the elemental composition was assessed via Atomic Absorption Spectroscopy (AAS). The results indicated that garlic and African basil exhibited the greatest concentrations of calcium (122.22 ± 9.62 mg/kg) and iron (7.25 ± 0.97 mg/kg), respectively. Conversely, garden lettuce and smooth amaranth showed the lowest levels of calcium (61.11 ± 9.62 and 72.23 ± 9.62 mg/kg, respectively). Smooth amaranth recorded the greatest magnesium content, measured at 74.56 ± 0.41 mg/kg, while garlic had the lowest value of 52.15 ± 0.93 mg/kg. Zinc levels ranged from 1.41 ± 0.49 mg/kg in garden lettuce to 3.11 ± 0.49 mg/kg in garlic. Critically, all measured metal concentrations remained within the permissible limits established by the World Health Organization (WHO), implying that consumption of these vegetables and spices poses no apparent risk to human health. Iodine content exhibited significant variability, with African basil (178.50 ± 55.50 µg/g) falling within the advocated range. Smooth amaranth (72.00 ± 9.00 µg/g) and garlic (42.00 ± 19.50 µg/g) presented iodine levels below the guideline, whereas garden lettuce (213.00 ± 85.50 µg/g) exceeded it. The outcomes of this investigation suggest that these vegetables and spices contribute significantly as sources of vital micronutrients in the diet. However, the observed variations in iodine content emphasize the importance of a balanced and diverse dietary intake.