Elemental concentrations in green vegetables from the perspective of urolithiasis risk

Abstract

Although green vegetables are valuable sources of essential elements, and are safe in that they lack harmful elements, they are high in oxalic acid, increasing the risk of urolithiasis. We performed elemental analyses on spinach (Spinacia oleracea L), Malabar nightshade (Basella alba), and water Morning Glory (Ipomoea aquatica), which contain large amounts of oxalic acid, and compared the data to those of Japanese mustard spinach (Brassica rapa var. perviridis), which is the second most commonly consumed green vegetable (after spinach) in Japan. We focused on concentrations of Ca, Mg, and Sr that suppress the formation of ureteral stones (calculi). The calcium concentration in spinach was [Formula: see text]g/g in leaves and [Formula: see text]g/g in stalks, and the level in Japanese mustard spinach were [Formula: see text]g/g in leaves and [Formula: see text]g/g in stalks. The overall Sr concentration in Japanese mustard spinach was thus 10-fold higher than in spinach, but the Mg concentration was lower than that in spinach. The concentrations of Ca and Sr in Malabar nightshade and water Morning Glory were 3- to 5-fold higher than in spinach. As the former vegetables are consumed much less often than spinach, the risk of urolithiasis is low. We explored how the concentrations of these elements changed after boiling.