Determination of oxalate content in commercial cranberry supplements

Kidney stones are a common ailment that is painful to individuals and costly to the US healthcare system. The vast majority of those kidney stones are composed of calcium oxalate, with or without calcium phosphate. Individuals prone to kidney stones follow dietary guidelines to reduce the chance of recurrence. These guidelines focus on lowering the amount of calcium and/or oxalate in the urine to prevent formation of new stones. Many vegetables and some fruits have sizable oxalate content and could contribute to stone formation. It is also known that supplementation with vitamin C is associated with higher oxalate excretion as oxalate is a metabolite of vitamin C metabolism. However, oxalate content of other types of supplements has not been quantified. In this study, we examine several cranberry supplements for their soluble oxalate content. Cranberry supplements are often recommended to patients with recurrent urinary tract infections and/or overactive bladder and are touted by advertisers as supportive of urinary tract health. The level of oxalate found in these supplements was low enough that their consumption would not be contraindicated for most kidney stone patients.