Many charts show varying levels of oxalate in vegetables, fruits and other plant based foods. Growing conditions, such as the season foods are grown effect oxalate levels. Oxalate has been shown to bind with calcium and other minerals in the intestines, thus making it an anti-nutrient. Research studies confirm the ability of oxalic acid in foods to lower availability of calcium and other minerals, the decrease is relatively small. This is also outweighed by the fact that there is so much more calcium, magnesium and iron in oxalate rich vegetables like spinach than the average vegetable in the first place that there will still be plenty of these minerals available to be absorbed!
It is also suggested that the body adjusts its natural manufacture of oxalic acid in response to fluctuating dietary intake. This study supports the small effect that oxalic acid containing foods have on oxalate urinary excretion. Only spinach, almonds and peanuts caused a small increase in urinary oxalate excretion.
It is now generally believed that the body can dispose of oxalic acid at even relatively high dietary quantities without trouble. Trouble arises for people who may have a genetic predisposition that impairs their bodies’ ability to process oxalic acid, so they may need to regulate their intake of it. Studies suggest that people with a history of heavy antibiotic use are at increased risk from oxalate consumption. Many antibiotics can kill the flora that degrades oxalate such as oxalobacter, and lactobacillus acidophilus and bifidus. Oxalobacter is a human intestinal bacteria that can reduce the urinary oxalate concentration following an oxalate load.
Those with kidney disorders, gout or rheumatoid arthritis, are typically advised to avoid foods high in oxalic acid, though increased water consumption may also help to mitigate potential risk. For a normal healthy person developing kidney stones from a high volume of oxalic acid in foods is very unlikely.
Since dietary oxalate accounts for only 10-15% of the oxalate that is found in the urine of individuals who form calcium oxalate stones, many researchers believe that dietary restriction cannot significantly reduce risk of stone formation.