Oxalates are naturally occurring organic compounds found in a wide variety of plant-based foods, including fruits, vegetables, nuts, and grains. These molecules are not inherently harmful and are part of plant defense mechanisms. For many people, consuming foods with oxalates poses no health concern, but for others managing specific dietary conditions, monitoring intake becomes necessary. The main question for those on a restricted diet is whether dried plums, commonly known as prunes, contain a high concentration of these compounds. This article provides a precise answer regarding the oxalate content of prunes for dietary management.
What Oxalates Are and Why They Matter
Oxalates serve a biological function in plants. When consumed, they bind to minerals in the human digestive tract, primarily calcium, leading to the formation of calcium oxalate crystals. In most healthy individuals, these compounds are simply excreted through the stool or urine without causing any issues.
The primary health concern related to high oxalate intake is the formation of kidney stones, as approximately 75% of all kidney stones are composed of calcium oxalate. When a person excretes high levels of oxalate in their urine, especially with low fluid intake, the concentration can lead to the crystallization and growth of stones.
A diet high in oxalates can interfere with the absorption of minerals like calcium and magnesium, as these nutrients become bound to the oxalate molecule. For individuals with a history of kidney stones or certain intestinal disorders, doctors often recommend a low-oxalate diet. This diet aims to reduce the body’s overall oxalate load to limit the risk of stone recurrence.
How Many Oxalates Are in Prunes
Prunes are generally categorized as a moderate-oxalate fruit, rather than being among the highest-oxalate foods. The precise measurement of oxalates in prunes can vary depending on the testing method, the ripeness of the fruit before drying, and the processing techniques used.
A typical serving of prunes, defined as about five medium-sized fruits or a quarter-cup portion, contains a moderate amount of oxalate. Dietary guides list this serving size as containing approximately 11 milligrams of oxalate. This level places them in the moderate category, which is defined as containing between 2 and 10 milligrams of oxalate per serving, or slightly higher.
For individuals following a strict low-oxalate diet, which often limits daily intake to 50 milligrams, a serving of prunes contributes a manageable percentage of that limit. While prunes are not considered a “low” oxalate food (less than 2 mg per serving), their content is significantly lower than high-oxalate items.
Navigating High-Oxalate Foods
To restrict oxalate intake, individuals should understand which foods contain the highest concentrations. High-oxalate foods include:
- Raw spinach (which can contain hundreds of milligrams per serving)
- Rhubarb
- Almonds
- Cocoa powder
- Beets
- Cashews
- Instant coffee
A mitigation strategy involves pairing oxalate-containing foods with a source of calcium during the same meal. When consumed together, the compounds bind in the intestine before absorption. This binding allows the calcium oxalate to pass harmlessly through the stool, reducing the amount of oxalate that reaches the kidneys.
Certain cooking methods can reduce the oxalate content of some vegetables. Boiling high-oxalate vegetables, such as spinach, can decrease their content by more than 50% as soluble oxalates leach into the cooking water. Discarding this water ensures the oxalates are removed. Drinking adequate water daily also helps by diluting the concentration of oxalate in the urine, making crystal formation less likely.