Content and daily intake of essential and potentially toxic elements from dietary supplements marketed in Nigeria

Concentrations of 19 elements (As, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, P, Pb, Sn, V, and Zn) were determined in 18 dietary supplements widely available on the Nigerian market. The purpose of the study was to assess their potential toxicity and adequacy to meet the respective recommended dietary allowance (RDA). Hg was quantified by atomic absorption spectrometry and other elements by inductively coupled plasma mass spectrometry or inductively coupled plasma optical emission spectrometry after closed vessel microwave digestion of samples. Method accuracy rates evaluated with certified reference materials (Peach, Tomato, and Spinach Leaves) ranged from 85 to 105% for the elements. Regarding essential elements, the highest concentrations (g/g) found in supplements were: Na 98400; Ca 82600; P 27800; Fe 9940; Zn 5980; K 5840; Mn 4090; Mg 2440; Cu 1470; Co 0.34; Mo 37.7; Ni 4.91; V 1.23; and Cr 18.3. Concerning toxic elements, the highest amount (g/g) found was As 1.13; Cd 0.2; Pb 1.86; Sn 0.49; and Hg 0.29. One daily dose of supplement contributed < 20% of the dietary intake requirement for five macro elements. Elemental contents above their RDAs (number of supplements in parenthesis) were: Mn (1); Cu (3); Mo (1); Fe (2); and Zn (2). The maximum allowable levels of Cu, Mn, Mo, Pb, and Zn were exceeded by 2, 3, 1, 6, and 2 supplements, respectively. The estimated daily intake (EDI) of 10 elements met the USP Advisory iiianel oral permissible daily exposure (PDE) recommendation. However, the EDI of Mn, Pb, and Zn; and Cu, Co, Fe, Ni, Pb, and Zn exceeded the limits set for oral PDE and other regulatory thresholds, respectively.