What are Oxalates and Their Impact?
Oxalates, or oxalic acid, are naturally occurring compounds found in many plants, including nuts, seeds, leafy greens, and legumes. For most healthy people, consuming oxalates is not a concern, and they are typically excreted from the body without issue. However, for individuals sensitive to oxalates or those with a history of calcium oxalate kidney stones, a high-oxalate diet can pose a risk. Oxalates bind to minerals like calcium and iron in the digestive tract, potentially hindering their absorption. A low-oxalate diet might be recommended for those prone to stone formation.
The Impact of Soaking on Walnuts
Soaking walnuts is a traditional practice that can help mitigate the effects of anti-nutrients. When walnuts are soaked in water, the soluble oxalates begin to leach out into the liquid. By discarding this water and rinsing the nuts thoroughly, you can effectively reduce the amount of oxalates consumed. While walnuts are already considered a low-oxalate nut compared to almonds, soaking offers an added layer of benefit, especially for those with sensitive digestive systems or specific health concerns.
Beyond oxalate reduction, soaking has several other benefits:
- Reduces Phytic Acid: Soaking helps break down phytic acid, another anti-nutrient that inhibits mineral absorption, thereby improving nutrient bioavailability.
- Enhances Digestibility: The soaking process neutralizes enzyme inhibitors, making the nuts easier for the body to digest.
- Improves Flavor and Texture: Soaking removes the bitter tannins present in the outer skin of walnuts, resulting in a milder, creamier, and more palatable flavor.
Soaking for Oxalate Reduction: A Step-by-Step Guide
To effectively reduce oxalates and other anti-nutrients in walnuts, follow these steps:
- Measure and Place: Measure out your desired amount of shelled, raw walnuts and place them in a clean glass bowl or jar.
- Add Water: Cover the walnuts with filtered water. Add at least double the amount of water to ensure the nuts remain submerged as they expand.
- Add Salt (Optional): For every four cups of walnuts, stir in a tablespoon of sea salt. The salt is believed by some to further aid in neutralizing enzyme inhibitors.
- Soak: Leave the walnuts to soak at room temperature for 8-12 hours, or overnight.
- Drain and Rinse: After soaking, drain the water thoroughly. This is a critical step, as the discarded water contains the leached oxalates and tannins. Rinse the walnuts well with fresh water.
- Dry: For longer storage, dehydrate the walnuts at a low temperature (below 150°F / 66°C) until completely crispy to prevent mold growth. If using immediately, they can be stored in the refrigerator for a few days.
Comparing Walnuts to Other Nuts for Oxalate Content
While soaking helps reduce oxalates, it's also helpful to understand how walnuts stack up against other common nuts. The following table provides a comparison of approximate oxalate levels, though values can vary based on sourcing and testing methods.
| Nut | Approx. Oxalate Content (mg per 100g serving) | Relative Oxalate Level |
|---|---|---|
| Walnuts | 54–62 mg | Lower-Moderate |
| Almonds | 369–469 mg | Very High |
| Cashews | 249–262 mg | High |
| Pecans | 10–25 mg per oz (low-moderate overall) | Low |
| Macadamia Nuts | ~42 mg | Low |
| Pistachios | ~50 mg | Moderate |
Soaking vs. Boiling for Oxalate Reduction
Some food preparation techniques, like boiling, can remove oxalates more effectively than soaking, particularly for high-oxalate foods like spinach. Boiling involves immersing food in boiling water for a specific period, which more aggressively leaches soluble oxalates into the water. However, for nuts, the high-heat exposure from boiling could potentially damage sensitive nutrients and alter texture. For walnuts, a simple overnight soak is a gentler approach that offers a good balance of reducing anti-nutrients while preserving nutritional integrity. If maximizing oxalate reduction is the priority, boiling and discarding the water is the most effective method, though it should be done carefully to avoid nutrient loss.
Is Soaking Walnuts Right for You?
For most people who consume a varied diet, the oxalate content in unsoaked nuts is not a concern. However, for those with a history of kidney stones, specific gut sensitivities, or anyone seeking to maximize nutrient absorption from plant-based foods, soaking is a beneficial practice. It’s also a great way to improve the flavor and texture of nuts, making them more enjoyable to eat. For individuals with a very high risk of kidney stones, dietary changes should always be discussed with a healthcare professional or dietitian. The decision to soak depends on your personal health needs and preferences.
Conclusion
In summary, does soaking walnuts reduce oxalates? Yes, soaking walnuts does reduce their soluble oxalate content, along with other anti-nutrients like phytic acid. While walnuts are already lower in oxalates than many other nuts, this process makes them more digestible and enhances nutrient availability, especially for those with digestive sensitivities or concerns about kidney stones. Proper soaking and drying are essential steps to ensure food safety and maximize the benefits of this traditional food preparation method.
