Evaluation of nutritional and toxicological significance of essential metal and iodine in vegetables and spices in Kogi metropolis, Nigeria

Iodine and some vital elements-calcium (Ca), iron (Fe), magnesium (Mg) and zinc (Zn)-levels were determined in four plant species that are widely used: Amaranthus hybridus , Lactuca sativa, Allium sativum , and Ocimum gratissimum . Iodine content was quantified via UV–Visible spectrophotometric analysis, whereas the levels of other elements were assessed using atomic absorption spectroscopy (AAS). All measurements were conducted using validated calibration procedures, with calibration curves exhibiting strong linearity (R 2 ≥ 0.995). Analytical accuracy and precision were verified through spike recovery tests (95–105%) and replicate measurements under quality-controlled conditions. The findings demonstrated distinct differences in mineral profiles across the samples. Allium sativum exhibited the highest calcium concentration (122.22 ± 9.62 mg/kg), whereas Lactuca sativa and Amaranthus hybridus showed comparatively lower values. Iron content was highest in Ocimum gratissimum (7.25 ± 0.97 mg/kg). The highest level of magnesium was establish in Amaranthus hybridus (74.56 ± 0.41 mg/kg) and the lowest level of magnesium was found in Allium sativum where 52.15 ± 0.93 mg/kg was obtained. The levels of zinc were 1.41 ± 0.49 mg/kg in Lactuca sativa and 3.11 ± 0.49 mg/kg in Allium sativum . All in all, the elemental concentrations measured were lower than the maximum allowable values provided by international and national regulatory authorities such as the National Environmental Standards and Regulations Enforcement Agency (NESREA), the World Health Organization, and no imminent toxicological hazard was observed. Iodine content varied substantially across the species, with Ocimum gratissimum within recommended limits, Amaranthus hybridus and Allium sativum below recommended levels, and Lactuca sativa exceeding the suggested range. These findings demonstrate that the studied plants are valuable sources of essential micronutrients, although iodine variability may influence nutritional adequacy. Therefore, a balanced and diverse dietary intake is recommended to ensure sufficient iodine consumption.