Oxalates, also known as oxalic acid, are naturally occurring compounds found in many plant-based foods, including fruits, vegetables, nuts, and grains. They are a topic of interest for people managing specific dietary concerns. This article addresses the frequent query of whether apples are high in oxalates and explains their role in a low-oxalate eating plan.
Understanding Dietary Oxalates
Oxalates are organic acids produced by plants to regulate calcium levels and deter pests. When consumed, these molecules travel through the digestive tract and bind to minerals, particularly calcium. This binding process ideally occurs in the gut, allowing the resulting calcium oxalate compound to be safely excreted in the stool.
If oxalates are not bound to calcium in the digestive system, they can be absorbed into the bloodstream and travel to the kidneys. There, a high concentration of unbound oxalate can combine with calcium in the urine, leading to crystal formation. For a subset of the population, this crystallization contributes to the formation of calcium oxalate kidney stones, the most common type of kidney stone.
The Oxalate Profile of Apples
Apples are considered a low-oxalate food. While all plant-based foods contain some oxalate, the amount in a typical apple is minimal compared to high-oxalate foods like spinach or rhubarb. Research indicates a single medium-sized, fresh apple contains a very low amount, often ranging from 1 to 5 milligrams (mg) of oxalate per fruit.
A food is generally classified as low-oxalate when it contains less than 10 mg of oxalate per serving. For perspective, a half-cup serving of cooked spinach can contain over 700 mg of oxalate. Most apple varieties, including Gala, Pink Lady, and Granny Smith, fall comfortably into the low-oxalate category. The oxalate content is generally distributed throughout the fruit, with no significant difference between the flesh and the skin.
Apples in the Context of a Low-Oxalate Diet
For individuals advised to follow a low-oxalate diet (typically limiting daily intake to 40 to 50 mg), apples represent a safe and versatile food choice. Their consistently low content makes them an excellent substitute for high-oxalate fruits and vegetables that must be limited, such as raspberries, kiwis, or potatoes. Apples can be consumed freely without the concern of significantly increasing urinary oxalate excretion.
Incorporating apples into meals can also contribute to a strategy of binding oxalates in the gut. Consuming low-oxalate foods alongside a source of calcium, such as a slice of cheese or a dollop of yogurt, helps ensure that any small amount of oxalate present is neutralized before it is absorbed into the bloodstream. This simple dietary practice maximizes the benefit of choosing a low-oxalate food like an apple.