Oxalates (oxalic acid) are naturally occurring compounds found in many plant foods, including nuts, vegetables, fruits, and grains. While they protect the plant, oxalates can be a dietary concern for some individuals. Monitoring oxalate intake is particularly relevant for people with specific health conditions, especially those who have a history of forming kidney stones. Understanding the oxalate content of common foods, like nuts, is important for managing a restricted diet.
Understanding Oxalate Function
Oxalates are often called “antinutrients” because they can interfere with the body’s ability to absorb certain minerals. When consumed, oxalates bind readily to positively charged minerals, especially calcium, in the digestive tract. This binding forms insoluble compounds, such as calcium oxalate crystals, which are usually excreted in the stool.
If the body absorbs too much oxalate, this compound is then sent to the kidneys for removal. In the kidneys, the excess oxalate can bind with calcium in the urine, leading to the formation of hard crystals. Since approximately 80% of kidney stones are calcium oxalate crystals, high dietary oxalate is a primary concern for susceptible people. Limiting oxalate intake is a common medical recommendation for those prone to stone formation or with certain kidney conditions.
Common Nuts with High Oxalate Content
The oxalate content in nuts varies considerably, and several popular types are considered high-oxalate foods that may need to be limited. Almonds have one of the highest concentrations, containing approximately 122 milligrams per one-ounce serving. Due to this high concentration, almond-based products like almond flour and almond milk are also monitored on low-oxalate diets.
Brazil nuts are another high-oxalate option, often containing around 137 milligrams per ounce, requiring strict moderation. Cashews (about 49 milligrams per ounce) and hazelnuts (around 63 milligrams per ounce) also contain significant levels. Pine nuts also rank highly, sometimes containing the most intestinal soluble oxalate, which is the fraction most readily absorbed by the body.
The Best Low-Oxalate Nut Options
For individuals managing oxalate intake, several nuts offer nutrient-dense alternatives with significantly lower levels.
Macadamia Nuts
Macadamia nuts are an excellent choice, consistently ranking as one of the lowest-oxalate nuts available. A one-ounce serving contains only about 12 milligrams of oxalate, making them a safer option for frequent consumption.
Pecans and Walnuts
Pecans are another safe option for a low-oxalate diet, typically containing around 10 milligrams per one-ounce serving. Although levels can vary based on growing conditions, pecans generally fall into the low-oxalate category. Walnuts are also a favorable choice, with a very low approximate oxalate content of 8 milligrams per ounce.
Other Low-Oxalate Options
Pistachios can be included when portion sizes are controlled, as they contain about 14 milligrams of oxalate per one-quarter cup serving. Dried coconut is notable for its minimal oxalate content, often registering close to zero milligrams per ounce, making it one of the most accommodating options for restricted diets. Choosing these options allows people to enjoy the nutritional benefits of nuts without significantly contributing to their daily oxalate load.
Preparing Nuts to Reduce Oxalate Levels
Beyond selecting naturally low-oxalate varieties, certain preparation techniques can help reduce the oxalate content of nuts, even those higher on the scale. Since oxalates are water-soluble, some will dissolve and leach out when exposed to liquid.
Soaking and Boiling
Soaking nuts in water for several hours can reduce the soluble oxalate content, though effectiveness varies by nut type. Boiling is considered one of the most effective methods, as it allows a greater amount of soluble oxalates to leach into the water. It is important to discard the soaking or boiling water, as this liquid contains the eliminated oxalates.
Pairing with Calcium
Another practical strategy involves pairing higher-oxalate nuts with calcium-rich foods during the same meal, such as dairy products or calcium-fortified milk. The calcium binds to the oxalates in the digestive tract, preventing them from being absorbed into the bloodstream and excreted by the kidneys.