Oxalic Acid and Kidney Stones:
- Oxalates, or oxalic acid, are compounds that occur naturally in many plants. Your body may also produce oxalic acid if you supplement with large amounts of vitamin C – doses of more than 2,000 milligrams a day. Calcium oxalate kidney stones form when high concentrations of calcium and oxalic acid are excreted in your urine.
- While some foods containing oxalic acid may promote stone formation in people prone to develop them, the University of British Columbia reports that the bioavailability of oxalic acid – how easily your body absorbs it – is more significant than the actual oxalate content of foods.
High Oxalic Acid Foods:
- Lists of foods high in oxalic acid vary greatly from source to source. The body is known to absorb oxalic acid from only a handful of foods, according to the University of British Columbia, including peanuts, pecans, wheat bran, spinach, rhubarb, beets and beet greens and chocolate.
- While other foods are considered high in oxalic acid, studies have not shown that the body readily absorbs their oxalate content. These include soy foods, sweet potatoes, black tea, berries and other dark leafy greens, like Swiss chard and collards.
Reducing Oxalic Acid:
- Eating oxalic acid foods together with calcium-containing foods such as yogurt, milk and other dairy products may reduce the risk of kidney stone formation, advises the University of Maryland Medical Center.
- In addition, a study published in 2005 in the “Journal of Agricultural and Food Chemistry” reported that several cooking methods help lower the oxalic acid content of vegetables. The researchers tested nine raw and cooked vegetables and found that boiling and steaming significantly reduce oxalic acid in vegetables with a high content of the compound, such as spinach.
- Although the role of diet in stone formation remains unclear, other factors do play a part. Health care professionals generally agree that drinking 2.5 liters or more of water a day, to maintain light-colored urine, decreases your risk of stones.
- The University of Maryland Medical Center suggests squeezing lemon juice into water, which helps boost the citrate levels in the urine and may protect against calcium oxalate stones. In addition, people who get adequate calcium from dietary sources – 1,000 milligrams daily for both men and women – have a lower risk of forming stones than those who don’t. UMMC warns against calcium supplementation, however, and notes that doses above 2,000 milligrams daily have a clear link to stone formation.
Source: Martinac, Paula; “Oxalic Acid Foods”, Demand Media, healthyeating.sfgate.com/oxalic-acid-foods-8447.html