Oxalate Reduces Calcium Availability in the Pads of the Prickly Pear Cactus through Formation of Calcium Oxalate Crystals

Abstract

The pads (nopales) of the prickly pear cactus are considered to be a good source of minerals and other nutrients on the basis of compositional analysis. In this study, this analysis is taken a step further by assessing the availability of selected minerals in nopales using an in vitro digestion and dialysis method. The results obtained suggest that although nopales are enriched in a number of minerals, their tissue calcium is not freely available. Microscopic analysis, energy-dispersive X-ray microanalysis, and oxalate measurements suggest that this reduction in available calcium is a result of its sequestration in the form of calcium oxalate crystals. The issue of mineral availability in plant foods is important when the dependence of many populations around the world on plant foods as their main source of minerals and other nutrients is considered.

Cactus stems (Opuntia spp.): A review on their chemistry, technology, and uses

“…In more recent studies, the mineral composition was reported to be 50, 18 -57, and 11 -17 mg/100 g dry weight for potassium, calcium, and magnesium, respectively, followed by manganese (62 -103 lg/g), iron (59 -66 lg/g), zinc (22 -27 lg/g), and copper (8 -9 lg/g) on a dry weight basis [18,27]. Again, these values should be considered approximate numbers since the mineral contents vary with species, site of cultivation, and the physiological state of the cladode tissue.…”

“…Furthermore, malic acid ranging from 95 to 985 mg/100 g fresh weight constitutes part of the free acid pool [29,35] being influenced by diurnal changes due to the CAM: the plant fixes carbon dioxide as malic acid and releases oxygen during the night to prevent water losses through transpiration. Malic acid is decarboxylated and the released carbon dioxide is converted into glucose via photosynthetic [21,27,40]. Moreover, oxalic acid has interesting inter-relationships with calcium and pectin metabolism [12,16,41].…”

“…Anyhow, its potential for gout treatment was claimed to be promising [179]. In this context, oxalic acid needs to be taken into consideration since calcium availability was found to be decreased due to sequestration by oxalic acid and high oxalic acid contents resulted in an enhanced urinary calcium oxalate excretion [27].…”

Hydroponic Cactus Pear Production, Productivity and Quality of Nopalito and Fodder

“…The increasing ash content due to maturity might reduce quality of the cladode as fodder since ash content is negatively correlated to digestibility (Pinos-Rodríguez et al, 2006). Notwithstanding, ash is a synonym of minerals (De Alba, 1971) and its input to the feeding of cattle and humans is relevant (Mcconn & Nakata, 2004).…”

Assessment of Ration Scales of the Armed Forces Personnel in Meeting theNutritional Needs at Plains and High Altitudes–I

“…The lower intake of iron poses no concern since its bioavailability is higher due to the presence of larger amounts of vitamin C. However, calcium intake was 2.5-fold greater than the RDA levels. Since the bioavailability of calcium from Indian diets being poor due to the presence of large amounts of phytates and oxalates, which are known to reduce absorption and bioavailability of minerals [26][27][28][29][30][31][32] , the higher intakes of calcium may not have any adverse effect.…”