Proximate composition and element contents of selected species of Ganoderma with reference to dietary intakes

Ganoderma is a wood-degrading mushroom that is treasured as a functional food since primitive times. Monitoring of macronutrient and element levels in mushrooms collected from the natural environment provides basic information in terms of safety, regulation, and nutrition. A comparative study was developed on the proximate and element contents of Ganoderma applanatum, G. brownii, G. lucidum, and G. philippii collected from different zones of the natural forests in Uttarakhand, India. These mushrooms revealed high amounts of proteins (9.29-12.4%) and carbohydrates (75.5-80.3%) and low contents of fats (1.62-2.87%), but ash (6.14-8.32%) and fibre (4.92-8.07%) were available in significant amounts. Element concentrations were determined by wavelength dispersive X-ray fluorescence (WDXRF) spectrometry. Calcium (5400-19,250 mg/kg) and potassium (2602-5601 mg/kg) were the predominant elements in mushrooms. The mushroom samples provided significant percentage contribution to reference recommended dietary intakes (RDIs) of essential elements such as calcium (27.0-96.3%), copper (58.2-95.8%), and manganese (37.3-62.3%), for adult males and females; and iron (35.3-97.1% for males and 28.6-78.6% for females), magnesium (7.06-11.5% for males and 7.74-12.6% for females), and zinc (6.35-19.8% for males and 7.65-23.7% for females). The studied mushrooms have no health risks as toxic metals such as aluminium and lead were detected below the legislated respective provisional tolerable intake values. Nutritional quality index (NQI) values revealed that mushrooms are densely rich in calcium, copper, iron, magnesium, manganese, and zinc.