Understanding Oxalates in Your Diet
Oxalates, or oxalic acid, are naturally occurring compounds found in many plants, including a variety of grains. For most healthy individuals, oxalates are harmless and are simply excreted by the body. However, for those with a history of calcium oxalate kidney stones, kidney disease, or specific gut conditions, managing dietary oxalate intake is crucial. When oxalates bind with calcium, they can form sharp crystals that accumulate in the kidneys, leading to painful kidney stones. While leafy greens like spinach and chard are famously high in oxalates, many grains also contribute significantly to dietary oxalate load.
The Top Grains with High Oxalate Content
Several grains are notable for their elevated oxalate levels, primarily due to their nutritional composition and how they are processed. The oxalate content is often concentrated in the bran, or outer layer, of the grain.
Whole Wheat and Wheat Bran
Among the most significant sources of oxalates in the grain category are whole wheat products, particularly wheat bran. Wheat bran has one of the highest oxalate contents among grains, containing approximately 457.4 mg of oxalate per 100g. Whole wheat flour and whole grain products like bulgur and couscous also contain considerable amounts, unlike their refined white flour counterparts. This is because the milling process removes the outer, oxalate-rich layers, but it also strips away many beneficial nutrients.
Buckwheat
Despite being a popular gluten-free option, buckwheat is a significant source of oxalates. Roasted buckwheat groats contain around 133 mg of oxalate per cooked cup. This makes it an important grain to monitor for individuals on a low-oxalate diet. However, for many, the nutritional benefits of buckwheat, such as its antioxidant content, outweigh the risks, assuming moderate consumption.
Amaranth
Amaranth, another pseudo-cereal often praised for its nutritional profile, is also high in oxalates. While some data on grain amaranth is less specific than for the leaves, studies indicate high oxalate levels, making it a point of consideration. Individuals with hyperoxaluria should approach amaranth with caution and consult a healthcare provider for personalized dietary advice.
Reducing Oxalate Levels in Grains
For those who need to manage their oxalate intake, preparing grains in specific ways can help reduce the total amount of oxalates consumed.
Soaking: Soaking grains like oats overnight can help draw out water-soluble oxalates. Discarding the soaking water before cooking is crucial for this method to be effective.
Boiling: Boiling grains in a pot of water and then draining the liquid (rather than cooking until the water is absorbed) can remove some of the oxalates. Instant oats, for example, have significantly lower oxalate content than steel-cut oats because they are parboiled during processing and the water is drained.
Pairing with Calcium: Consuming high-oxalate grains alongside calcium-rich foods can help bind oxalates in the gut before they can be absorbed by the body. Good sources of calcium include dairy products like cheese or yogurt, or calcium-fortified foods.
Comparison of Oxalate Content in Common Grains
To help visualize the difference, here is a comparison table of the approximate oxalate content for several grains based on available data.
| Grain (Cooked, per 1 cup) | Approximate Oxalate Content | Classification |
|---|---|---|
| Buckwheat Groats | 133 mg | High |
| Quinoa | 54 mg | Moderate to High |
| Brown Rice | 24 mg | Moderate |
| Oatmeal (Old-Fashioned) | ~22 mg | Low to Moderate |
| White Rice | <10 mg | Low |
| Cornmeal/Grits | ~45 mg | High |
*Note: Oxalate values can vary widely depending on preparation, specific variety, and testing methods.
Low-Oxalate Grain Alternatives
For those needing to strictly limit their oxalate intake, several grains offer a safer alternative:
- White Rice: Refined white rice has a very low oxalate content compared to brown rice, as the outer bran has been removed.
- Millet: Some sources classify millet as a moderate oxalate grain, but it is generally considered a safer choice than the high-oxalate alternatives.
- Cornmeal/Corn Bran (Raw): Raw corn bran is noted as a low-oxalate option, contrasting with the higher content in cooked cornmeal.
- Refined Wheat Products: While not whole grain, white bread, and most refined wheat pastas are lower in oxalates.
Conclusion: A Balanced Approach to Grains
In summary, for individuals needing to manage their oxalate intake, understanding which grains are highest in oxalates is a key part of diet planning. Grains like whole wheat bran, buckwheat, and amaranth are among the highest contributors. However, for most people, these nutritious foods can be enjoyed in moderation as part of a balanced diet. Those at higher risk for kidney stones or other oxalate-related health concerns should consult a healthcare professional or registered dietitian for guidance on their personal dietary needs. By adopting preparation methods like soaking and boiling, and pairing high-oxalate foods with calcium sources, individuals can effectively manage their intake while still benefiting from the nutritional value of these whole foods. You can find more detailed information on managing dietary oxalates at the Cleveland Clinic website.
