Investigating Trace and Macro-element Composition of Herbal and Nutraceutical Dietary Supplements Marketed in Oman: Insights into Safety and Labeling

With the global increase in the use of dietary supplements to provide nutrients in one's regular diet, these supplements' potential health risks and benefits have become a topic of significant interest. Interestingly, as dietary supplements, the Food and Drug Administration (FDA) in the United States (USA), Europe, and most countries do not require manufacturers and distributors to obtain approval or provide safety assessments before marketing those products. This research explores for the first time 16 heavy, trace and macro-elemental contents, namely, As, Ni, Cd, Pb, Cu, Co, Mn, Cr, Zn, V, Fe, Al, K, Na, Mg, and Ca, within 24 nutraceutical and herbal supplements marketed in Oman. The research is focusing on ensuring their compositions, concentrations, and freedom of toxic elements. ICP-OES was utilized, preceded by a microwave digestion technique to digest the samples in concentrated HNO3 and HCl (3:1, v/v). The method was validated within linear ranges of 0.03-5.00 ppm and 1.0-200.0 ppm for micro- and macro-elements, respectively, with %recoveries ranging from 90 to 104%. The limits of detection ranged from 0.01 to 0.09 and 0.14 to 0.30 ppm, while the limits of quantification ranged from 0.03 to 0.28 and 0.46 to 0.91 ppm for micro- and macro-elements, respectively. The detected levels were compared to online databases for risk assessment. Although As and Cd were not detected in all samples, Pb was found in nine samples, with some exceeding regulated limits of exposure. About 80% of the samples contained Al, of which two samples were susceptible to serious health risks of exceeding exposure limits in their compiled doses. The locally harvested Omani herbal supplements revealed significant amounts of Zn, Mg, Mn, and Cu. The results highlighted the potential risks associated with both dosage compliance and labeling discrepancies.