Oxalate in plants, amount and methods to reduce exposure; a systematic review

Plants have a great impact on human health. Oxalate is a harmful compound found in some plants. Oxalate interferes with digestion and absorption of nutrients. Furthermore, the origin of most kidney stones is caused by calcium oxalate. Consumption of these plants in the diet of people with kidney stones should be limited. This review identifies plants with high oxalate and also introduces a proven strategy to reduce exposure to oxalates. In this study, search was performed with the keywords of dietary exposure, amount, evaluation, oxalate, and food on Scopus, PubMed, Science Direct, and Web of Science. Manuscripts of the last ten years were considered. 576 studies were obtained and 35 articles were finally chosen according to exclusion and inclusion criteria. Among the plants, the highest amount belongs to the Licorice with 3569.3 ± 319.7 mg/100g. The amount of oxalate in unripe fruits is also higher. Large amounts of oxalate have been reported in some high-consumption plants around the world, including spinach, sweet potatoes, Brassica spp, white beans, soybeans, fenugreek, and onions. Furthermore, to reduce the amount of exposure, good agricultural practices to prevent oxalate accumulation in plants, boiling high oxalate plants, consumption of calcium supplements, probiotics, and dairy foods are recommended.