What are oxalates?
Oxalates, or oxalic acid, are naturally occurring compounds found in many plants. In the human body, oxalates can bind with minerals, primarily calcium, to form calcium oxalate crystals. While for most healthy individuals this process poses no issue and the crystals are simply excreted, for those with predispositions to kidney stones, gout, or specific kidney diseases, this can be problematic. In plants, oxalates can also act as a defense mechanism against predators.
Wood sorrel's oxalate content and comparison
Wood sorrel's genus name, Oxalis, is derived directly from the Greek word for sour, in reference to its oxalic acid content. The concentration can vary depending on the specific species, plant maturity, and growing conditions. However, several sources confirm wood sorrel's relatively high oxalate levels. A 2024 paper reported a dry weight oxalic acid content of approximately 102mg/g in one species, O. pes-caprae. This value is significantly higher than that of common vegetables like spinach, though due to its low fresh weight, the amount consumed during foraging is typically minor.
Wood Sorrel vs. Other Oxalate-Rich Foods
| Food Item | Total Oxalate (mg/100g Fresh Weight) | Notes on Content |
|---|---|---|
| Wood Sorrel | ~2242 mg/1000g* | Contains high concentration, but typical consumption is small. |
| Spinach | ~1124 mg/1000g* | Widely known for high oxalate content; large servings can lead to high intake. |
| Rhubarb Leaves | ~500 mg/100g | Very high and toxic, should not be consumed. |
| Swiss Chard | ~1458 mg/100g | High oxalate content, especially in leaves. |
| Beets | >50 mg/100g | Considered a high-oxalate food. |
*Note: Fresh weight oxalate values for wood sorrel and spinach derived from dry weight comparisons, showing that while wood sorrel is more concentrated, spinach is often consumed in larger quantities.
Who should be cautious with wood sorrel?
While healthy individuals can typically consume wood sorrel in moderation without issue, certain people should exercise caution or avoid it entirely due to its oxalate content.
- Kidney Stone Sufferers: As calcium oxalate is the primary component of most kidney stones, a high-oxalate diet is a concern for those prone to stone formation. The crystals from excess oxalate can exacerbate the condition.
- Those with Kidney Disease: High oxalate levels can further stress compromised kidneys and can lead to a condition called oxalosis in severe cases, where oxalate deposits build up in organs and tissues.
- Individuals with Gout or Rheumatoid Arthritis: There is a theory that oxalate crystals can deposit in joints, causing inflammation and pain, though more research is needed.
- Pregnant and Breastfeeding Women: Due to potential risks, some sources advise caution for expectant or nursing mothers.
- People with Gut Dysfunction: Individuals with inflammatory bowel disease or those who have had certain surgeries may absorb more oxalates than healthy individuals.
Reducing oxalate content
For those who wish to enjoy wood sorrel while minimizing oxalate intake, certain preparation methods can help reduce the levels.
- Boiling: This is the most effective method, as a portion of the water-soluble oxalates leaches into the boiling water. The cooking water should then be discarded.
- Steaming: While less effective than boiling, steaming can still help reduce the oxalate content of greens.
- Pairing with Calcium-Rich Foods: Eating wood sorrel with a source of calcium, such as cheese, can cause the oxalates to bind to the calcium in the digestive tract, reducing the amount absorbed by the body.
A note on moderation and identification
Like many foraged edibles, wood sorrel is best enjoyed in moderation. A handful of leaves added to a salad provides a pleasant tart flavor with minimal risk. It is important not to confuse wood sorrel with clover, as the leaves are very similar. Wood sorrel has distinctive heart-shaped leaflets, while clover has rounded ones. The genus name Oxalis is a helpful reminder of the sour, acidic taste due to its oxalic acid content, which is present in the leaves, flowers, and stems. Foragers should be absolutely certain of their identification before consuming any wild plant. Find more foraging information at The Grizzly Forager
Conclusion
In short, wood sorrel is indeed high in oxalates, the compound responsible for its characteristic lemony tang. For most healthy individuals consuming small, culinary portions, this is not a concern, much like eating spinach or rhubarb stalks. However, those with a history of kidney stones, kidney disease, gout, or specific gut issues should approach consumption with caution or avoid it. Using proper cooking methods, such as boiling and discarding the water, and pairing with calcium-rich foods can further mitigate the risk. As with any wild food, moderation and correct identification are the most important considerations for a safe and enjoyable experience. Always consult a healthcare professional before significantly altering your diet, especially if you have existing health conditions.
