Kidneys and Oxalate Content, Which Foods To Avoid

Oxalate (Oxalic Acid) and Kidney Health
The categorization of foods by oxalate content and antioxidant activity grants more informed nutritional suggestions for patients with urolithiasis and other diseases, according to a recently published study.

What is Oxalate?
Oxalate is any salt or ester of oxalic acid, occurring in plants, especially spinach, rhubarb, and certain other vegetables and nuts, and capable of forming an insoluble salt with calcium and interfering with its absorption by the body.

If there is too much oxalate content and too little liquid in the urine, calcium oxalate fragments create crystals. As the crystals begin to increase in number, they stick to one another to form a larger crystal known as a kidney stone. Kidney stones are a big concern for those who have underlying kidney disease or those who are at risk for kidney disease. For serious patients undergoing dialysis or dealing with CKD, here are some foods that you should avoid that have high oxalate:

  • Beans


  • Beer


  • Beets


  • Berries


  • Chocolate


  • Coffee


  • Cranberries


  • Spinach


  • Nuts


  • Oranges


  • Rhubarb


  • Soda


  • Soy beans


  • Soy milk


  • Sweet potatoes


  • Tea (black)


  • Tofu


“The combination of obesity and excessive oxalate consumption is an important factor in the development of kidney stones and metabolic disorders,” Azalea Avila-Nava, PhD, of Hospital Regional de Alta Especialidad de la Peninsula de Yucatan, and colleagues wrote. “The aim of this study was to determine the oxalate content and antioxidant activity of different types of foods, including ethnic foods, to provide evidence and generate a database for supporting the nutritional management of the kidneys of patients who experience kidney stone formation.”

In the study mentioned above, the oxalate content of around 100 foods were assessed using enzymatic assay and antioxidant activity by oxygen radical absorbance capacity to determine the oxalate/antioxidant ratio. Researchers assessed consumption in 400 individuals classified as obese through 24-hour dietary recalls. Lab results revealed the foods with the highest oxalate content were raw spinach (960mg/100g), purslane (418mg/100g), chard (350mg/100g).

Strawberries, chocolates, roselle, morita peppers and pinolillo had the highest antioxidant activity. Oxalate consumption in participants who were categorized as obese was found to exceed consumption recommendations.

In conclusion, this research conducted provides valuable information and helps people generate feasible options for food planning and overall suggestions for oxalate-restricted diets. For more on CKD and diet, be sure to check out our YouTube Videos and our Complete Guide to Renal Diets in the shop.