Micronutrient mineral content of the fruiting bodies of Australian cultivated Agaricus bisporus white button mushrooms

Agaricus bisporus white button mushrooms (WBM) obtained from two farms were analyzed using inductively coupled plasma-mass spectrometer (ICP-MS) for minerals (Na, K, Mg, Ca, Mn, Fe, Cu, Zn, Se, Mo, Co, Cr, Pb, Cd, Si, B and V), and for the capacity to provide a dietary source of selected minerals (Na, K, Mg, Ca, Mn, Fe, Cu, Zn, Se, Mo and B). WBM contained Cu at levels of >30%, Se at levels >13% and Mo at levels of 6.4-10% of daily Required Dietary Intake (RDI) based on average values for adults as defined by Australian National Health and Medical Research Council (NHMRC). Boron (B) was found in the range of 72.4-1298.7 μg per 100 g serving. While the RDI for B has not been defined by National Health and Medical Research Council (NH&MRC), WBM contained on average >20% of RDI as defined by National Academy of Sciences (NAS). WBM contained on average 6.1% for Na, 3.4% for K, 4.1% for Mg and 0.7% for Ca daily RDI, all of which were nutritionally insignificant. Mn was found at relatively high concentrations ranging from 76.3 to 210.7 μg/100 g serving. When defined as % of daily RDI (NAS), it was considered nutritionally insignificant with values ranging from 1.9% to 3.9%. Accumulation of toxic heavy metals such as Pb and Cd was found in WBM (14.4-61.6 μg/100 g for Pb, and 0.2-2.6 μg/100 g for Cd, respectively) but the levels were below the safety limits defined by FAO/WHO for weekly intake. Both compost and casing contained high levels of minerals, and are the likely sources of mineral elements in WBM. While there were variations in mineral contents of WBM harvested from 1st, 2nd and 3rd flushes in the two farms, the differences were not statistically significant. Taken together, the results showed that A. bisporus white button mushroom can provide significant contribution to the daily requirements of several minerals from the point of view of human nutrition, and in particular, Cu, Se, Mo and B.