While practitioners are aware that a low-oxalate diet can mitigate the risk of kidney stones, it’s less commonly known that oxalates can exacerbate or trigger other conditions in susceptible individuals. Despite the inclusion of many high-oxalate foods in diets typically considered “healthy,” their potential impact may not be readily apparent. This discussion aims to clarify the nature of oxalates and the rationale behind reducing their intake for certain patients. Here are the key points for clinical consideration.

What are oxalates?

Oxalate (or oxalic acid) is a molecule that occurs naturally in the human body and in a wide range of plant-based foods. Although oxalates are not required for bodily functions, they are metabolized and excreted through urine and stool, combined with other waste materials.

Can oxalates cause problems?

While most individuals can eliminate about 90% of oxalates ingested, those with a high intake or underlying health conditions may experience difficulty in excretion. Accumulation of oxalates can lead to the formation of calcium oxalate crystals, impeding calcium absorption and potentially resulting in kidney stones, the most common type being calcium oxalate stones.

Oxalate build-up can also interfere with nutrient absorption. As mentioned, oxalates tend to attach to minerals in the gut, which prevents the minerals from being absorbed. For example, spinach, which has a high amount of calcium and oxalate, can stop calcium from being absorbed. One study showed that fiber and oxalates have a similar interaction, leading to drops in levels of zinc, magnesium, and calcium after one week on a high-oxalate diet.

Who should follow a low-oxalate diet?

A low-oxalate diet may benefit individuals with specific health profiles:

• Those with kidney stones: Calcium oxalate stones, the most common type of kidney stones, are caused by too much oxalate in the body. People who have had at least one kidney stone are advised to lower oxalate consumption.
• Antibiotic users: O. formigenes is a type of bacteria in the gut that feeds off oxalates and significantly reduces their build-up. While antibiotics are sometimes necessary, they can wipe out this strain of bacteria in the gut. Those with a long history of antibiotic use may need to reduce oxalates as their microbiome rebalances.
• Those with leaky gut: As mentioned earlier, a build-up of oxalates can interfere with nutrient absorption. Leaky gut, a condition that also affects the gut’s ability to absorb nutrients, can compound this effect.
• Children with or at risk for autism spectrum disorder (ASD): Science has found a potential link between oxalates and the development of ASD. Studies have shown that children with autism may display impaired kidney function, making it more difficult to process oxalates.
• Those with hyperoxaluria or hypercalciuria: These rare conditions result in chronic kidney and bladder stones caused by an overproduction of heightened absorption of oxalates.
• Potentially those with autoimmune disorders: Oxalates in the diet can reduce mineral absorption and use up valuable bodily detoxification resources. This may contribute to gut dysbiosis—a potential contributing factor of autoimmune and inflammatory diseases.
• Other conditions: These conditions may also have a link to oxalates in the diet: urinary tract infections, vulvodynia, yeast overgrowth, fibromyalgia, pain, neurological symptoms and more.

Which foods are high in oxalates?

So, what does a low-oxalate diet look like? Here are some common foods with high levels of oxalates that should be avoided on a low-oxalate diet: