Oxalates, or oxalic acid, are organic compounds primarily found in plant sources, although they can also be synthesized endogenously within the human body. Common plant sources containing oxalates include fruits, vegetables, nuts, and legumes. The Dietary Guidelines for Americans (2020-2025) encourage healthy dietary patterns throughout all stages of life, emphasizing the consumption of nutrient-dense foods that promote overall health. Healthy individuals may incorporate foods with oxalates in moderation as part of a phytonutrient-rich and balanced diet.
Who Should Reduce Oxalates in Their Diet?
For individuals following a vegan or vegetarian diet or those with a history of kidney stones, understanding how to manage oxalate intake may benefit overall health.
Vegan and Vegetarian Diets
Well-planned vegan and vegetarian diets are often phytonutrient and antioxidant-rich, supporting immune health and the gut microbiome. Nevertheless, there may be insufficient intake of critical nutrients that can only be obtained from animal-based food sources. Anti-nutritive compounds found in plant-based foods, including oxalates and phytates, have the potential to hinder nutrient absorption further.
Dietary oxalates are considered “anti-nutrients,” as their presence may interfere with nutrient bioavailability and absorption. However, knowing one cannot avoid them entirely, it may be comforting to know that plant-based soluble oxalates have been shown to have several beneficial functions, including calcium regulation and the ability to detoxify heavy metals, when consumed in moderation. Nevertheless, for vegetarians or vegans who regularly consume large amounts of plant-based foods, it is helpful to consider strategies that reduce anti-nutrient content. These include soaking grains and nuts before consumption and using cooking techniques like boiling or steaming to minimize their effects. It’s also wise to be mindful of the quantity of oxalate-rich food in the diet.
Individuals with Kidney Stone Risk
Recurring kidney stone formation (known as nephrolithiasis) is driven by urinary supersaturation and the crystallization of excess substances, including amino acids (cysteine), purines (2,8-dihydroxyadenine and xanthine), calcium oxalates, calcium phosphate, uric acids, and urates. The primary contributors to crystal formation are calcium, oxalate, urate, and phosphate ions, which are regulated by several mechanisms, one of which is altered calcium and vitamin D regulation.
Despite the multifaceted nature of kidney stone formation and progression, dietary manipulation can be a crucial strategy in managing the condition and mitigating risk. Since approximately 75% of kidney stones are formed from calcium oxalate, dietary recommendations include minimizing high-oxalate foods, keeping dietary oxalate intake between 50 mg and 100 mg daily, and incorporating phytonutrient-rich foods that may help reduce the risk of kidney stones. Other dietary factors, such as increasing hydration and calcium intake, reducing sodium, and limiting animal protein, may also contribute to lowered risk.
Common Foods High in Oxalates
Common Foods Low to Moderate in Oxalates
4 Preventative Steps to Mitigate Kidney Stone Risk
Consuming low to moderate oxalate foods should not be the only focus for individuals concerned with kidney stone formation. A multifaceted approach is essential, as simply reducing high-oxalate foods in the diet may not offer the same level of risk reduction for kidney stones as incorporating the additional benefits of sufficient dietary calcium, reduced sodium, limited animal protein, and adequate hydration.
1. Reducing Sodium Intake
A higher sodium intake is associated with an increased susceptibility to calcium oxalate stone formation, as increased calcium excretion may lead to reduced oxalate binding. In a three-month randomized controlled trial (n = 210) conducted on patients with idiopathic calcium oxalate nephrolithiasis, a low-salt diet effectively reduced calcium excretion and corrected hypercalciuria in 30% of the cases.
A large prospective cohort study conducted over 50 years examining the association between a DASH-style diet and the incidence of kidney stone formation showed a significant decrease in kidney stone risk. DASH (Dietary Approaches to Stop Hypertension) dietary guidelines have established sodium intake limits of 1,500 to 2,300 mg daily while increasing fruits and vegetables and calcium intake concurrently. Increasing the total daily servings of fruits and vegetables with low to moderate oxalate levels may increase urinary citrate, providing inhibitory actions to calcium oxalate stone formation. While the categorization of oxalate levels as low, moderate, or high varies among resources, combining low to moderate oxalate intake with other dietary strategies is a key method for reducing kidney stone risk.
2. Increasing Dietary Calcium
Similarly, dietary calcium plays a significant role in urinary oxalate excretion. Dietary calcium intake is inversely related to levels of oxalate absorption. Along with decreasing high-oxalate food intake, consuming 1,000 to 1,200 mg/day of calcium is recommended.
In a dietary study spanning five years, adhering to a diet with sufficient calcium intake (~1,200 mg/day) while lowering intake of sodium and animal protein was more effective at reducing the risk of recurrent idiopathic calcium oxalate stones versus following a low-calcium diet (<400 mg/day).
A four-year community-based cohort study (n=149) assessed variations in calcium and vitamin D metabolism among first-time patients with calcium-related kidney stones. This was done by measuring serum levels of calcium, vitamin D (including both calcidiol and calcitriol), parathyroid hormone, and fibroblast growth factor-23 (FGF-23). Findings suggest elevated serum calcium and calcitriol may potentially increase urinary supersaturation, driven by factors such as vitamin supplementation, dehydration, or sunlight exposure. This increase may elevate the risk of crystallization associated with calcium and subsequent stone formation. Although serum PTH levels do not appear to be responsible for increased calcitriol synthesis, a trend was observed indicating elevated PTH concentrations in first-time kidney stone patients, suggesting slight alterations in the regulatory activities of the parathyroid gland.
3. Ensure Adequate Hydration Levels
Adequate fluid intake is recognized as a crucial factor and is considered an essential initial strategy for preventing kidney stones. An in vitro study (n = 16) on stone formation found that higher fluid volumes reduced calcium oxalate crystallization and aggregation in both patients with a history of kidney stones and those without.
In a prospective study conducted over 32 months, renal papillary density was evaluated in patients with recurrent calcium oxalate stones (n = 25) following a 12-month period of an increased hydration regimen. Consuming at least 2 L per day led to a significant reduction in renal papillary density, an increased crystal elimination rate, and also affected crystal cell adhesion. Numerous studies suggest a fluid intake of 2.5 to 3.0 L per day to ensure a minimum urinary output of 2.0 to 2.5 L daily for kidney stone prevention.
4. Prioritize Plant-based Protein and Limit Animal-based Protein
Proteins play a critical role within the body and are necessary for cellular function. Current recommendations for animal protein intake are conservatively between 0.8 and 1.0 g per kg of body weight daily for individuals with a higher risk of kidney stones.
Elevated dietary protein intake (> 2.0 g/kg/day) of all kinds may raise the risk of calcium-related stone formation. Twenty-four-hour urinalysis testing suggests high protein intake may contribute to abnormal values in calcium excretion, citrate, uric acid, pH, urea nitrogen, protein catabolic rate, and sulfates. Notably, animal proteins contain high levels of purine and sulfur, which also may affect urine pH levels.
Alternatively, a large prospective study (n = 42,919) examined various protein types (vegetable, dairy, and non-dairy animal protein) and the incident risk of kidney stones. Findings suggest vegetable proteins were not associated with kidney stone risk versus non-dairy animal proteins. Increased potassium consumption was also significantly correlated with reduced risk, suggesting that a diet abundant in fruits and vegetables may offer substantial health benefits.
Best Practices for Preparing and Cooking Oxalate-rich Foods
Learning the best methods for preparing and cooking foods high in oxalates may help decrease the overall consumption of oxalates and improve mineral availability. Boiling, soaking, and steaming vegetables have been shown to significantly reduce soluble oxalates by 30% to 87%. While timeframes vary depending on the food, studies indicate that soaking dry beans overnight before boiling can reduce oxalates by nearly 60%. Alternatively, canning is another effective method, leading to an increase in oxalate loss between 85% to 93%. Since soluble oxalates can be more easily absorbed, being mindful of the cooking methods used for oxalate-rich foods may help lower overall oxalate exposure.
Understanding the role of oxalates and how to manage them within the diet can benefit an individual’s health and nutrient status while striving for a nutritionally dense and phytonutrient-rich diet. Factors such as reducing oxalate-rich foods, ensuring proper hydration, lowering sodium intake, increasing dietary calcium, and limiting animal protein can offer significant benefits for oxalate metabolism.
To learn more about a well-rounded, nutrient-dense diet:
Hungry for More: Nutrition Gaps in the Modern American Diet
Nutrition Gaps: 5 Things to Do and Avoid in 2025
By Rachel B. Johnson, MS, CNS, LDN
Designs for Health has been dedicated to being the most trusted source for superior quality, science-based nutritional products for nearly three decades. We’re committed to maximizing successful health outcomes by providing healthcare practitioners with comprehensive support through our extensive product line, ongoing clinical education, and practice development programs. The blogs we publish here cover a range of topics, including new and original approaches to diet and healthcare, analyses of the latest cutting-edge research, deep-dives into specific nutrients, botanicals, nutraceuticals and more, all fully referenced for those who want to dig deeper into the primary literature.
