Understanding Oxalates in Food
Oxalates, or oxalic acid, are naturally occurring compounds in many plants. When consumed, they bind to minerals like calcium during digestion. This can prevent the body from absorbing those minerals, but it is typically a non-issue for most healthy individuals who consume a balanced diet. The primary health concern arises for people predisposed to kidney stones, as the binding of calcium and oxalates in the kidneys can lead to the formation of painful calcium oxalate crystals. High-oxalate foods include spinach, rhubarb, almonds, and instant tea.
Nasturtium's Oxalate Profile
Nasturtium (Tropaeolum majus) is a common garden plant known for its vibrant edible flowers and peppery leaves. While many resources highlight its rich content of vitamins (C, A, D) and minerals (potassium, phosphorus, calcium), the oxalate content is rarely emphasized because it is not a significant concern for most consumers. Unlike spinach, which can contain hundreds of times more oxalate than low-oxalate greens, nasturtium is not in the same league. An extract study on the related Nasturtium officinale (watercress) confirmed the plant's oxalate content but did not show significant effects on calcium oxalate stone formation in rats, particularly at low doses, reinforcing the idea of a moderate risk.
How Nasturtium Compares to High-Oxalate Foods
To put the nasturtium's oxalate levels into perspective, consider the following comparison. A standard serving of spinach can contain hundreds of milligrams of oxalates, while the same quantity of nasturtium leaves contains a far lower concentration. This difference is why a single cup of spinach can contain the same amount of oxalate as hundreds of cups of a low-oxalate green like kale. For nasturtium, the quantity needed to reach a problematic level would be extremely high and well beyond normal dietary intake.
Factors Influencing Nasturtium Oxalate Content
Several factors can influence the oxalate content in any plant, including nasturtium:
- Plant Maturity: Younger, more tender leaves generally have lower oxalate concentrations than older, tougher leaves. This is consistent with anecdotal evidence from gardeners who note the milder flavor of young leaves.
- Soil and Growing Conditions: The mineral content of the soil and general growing conditions can influence a plant's chemical composition. However, these effects are typically minor compared to the plant's inherent genetics.
- Preparation Method: Cooking can significantly reduce oxalate levels in water-soluble vegetables. Boiling nasturtium leaves and discarding the water is the most effective way to lower their oxalate content, though steaming and soaking also help.
Reducing Oxalate Intake from Nasturtium
For those with a high risk of kidney stones, or who are otherwise concerned, several strategies can help minimize oxalate intake from nasturtium or any other plant:
- Pair with Calcium-Rich Foods: Consuming calcium-rich foods, such as cheese or nuts, alongside nasturtium can help bind the oxalates in the gut, reducing their absorption into the bloodstream. A nasturtium pesto with Parmesan cheese or a salad with nuts is a delicious and effective combination.
- Blanching or Boiling: Boiling the leaves for a minute and then discarding the water will cause a significant amount of the water-soluble oxalates to leach out. This is a simple technique to reduce oxalate exposure, particularly when using a large quantity of leaves for a pesto or sauce.
- Moderation is Key: As with any food, moderation is the best approach. Enjoying nasturtium leaves and flowers as a garnish or a minor ingredient in salads is unlikely to pose a risk to anyone, even those with oxalate sensitivities.
Nasturtium vs. High-Oxalate Greens: A Nutritional Comparison
| Feature | Nasturtium | Spinach (High-Oxalate) |
|---|---|---|
| Oxalate Content | Relatively low | Very high |
| Vitamin C | Excellent source, rivals citrus | Good source |
| Flavor | Peppery, mild to spicy | Mild, earthy |
| Cooking effect on oxalates | Boiling effectively reduces content | Boiling is recommended to reduce, but still high |
| Health Risk for Stone-Formers | Low risk with moderate intake | Higher risk with regular, large consumption |
| Best Consumption Method | Raw in salads, pesto; cooked with boiling | Cooked, with calcium sources; consumed moderately |
The Role of Nasturtium in a Balanced Diet
Nasturtium leaves offer numerous health benefits, including high levels of vitamin C, antioxidants, and a natural antimicrobial effect. They are a valuable addition to a diet when consumed in reasonable amounts. The risk associated with their oxalate content is negligible for most people. For individuals with a history of kidney stones or other oxalate-related concerns, being mindful of overall oxalate intake and utilizing cooking methods that reduce content is prudent. This doesn't mean avoiding nasturtium, but rather enjoying it mindfully. For example, preparing a nasturtium pesto with a calcium-rich cheese is an excellent way to balance out the potential antinutrient effects.
Conclusion
While it is true that nasturtium leaves contain oxalates, they are not classified as a high-oxalate food like spinach or Swiss chard. For the vast majority of the population, consuming nasturtium leaves in moderation is perfectly safe and can even contribute to a healthy diet thanks to their rich vitamin and mineral profile. For those concerned about oxalate intake, simple culinary techniques such as boiling and combining with calcium-rich foods can further mitigate any risk. Ultimately, the pleasure and nutritional benefits of this vibrant, edible plant far outweigh any minimal oxalate-related concerns for most people.
Nasturtium Leaves and Oxalate Concerns
Takeaway: Nasturtium leaves do contain oxalates, but in low concentrations that are safe for most people to consume in moderation.
Relative Oxalate Levels: Compared to high-oxalate foods like spinach and rhubarb, nasturtiums pose a significantly lower risk for oxalate-related issues.
Reducing Oxalate Content: Boiling or blanching nasturtium leaves and discarding the water is an effective method for reducing their soluble oxalate levels.
Nutrient Absorption: While oxalates can bind to minerals like calcium, the overall nutritional benefits of nasturtium are still significant, particularly its high vitamin C and antioxidant content.
Risk Factors: Individuals with a history of kidney stones should be mindful of their overall oxalate intake, including from nasturtium, though moderate consumption is still generally safe.
Optimal Consumption: Enjoying nasturtium leaves in salads, pestos, or cooked dishes in moderation is a safe way to benefit from their flavor and nutrients.
Culinary Combination: Pairing nasturtiums with calcium-rich foods, such as cheese, can help mitigate the absorption of oxalates.
