Oxalates are organic compounds found in many foods, including some of the healthiest vegetables and nuts. While they are a natural part of a diverse diet, understanding their potential impact on bone health and overall well-being is important, especially for individuals with specific health conditions. 

Oxalates at low levels play a role in normal metabolic processes, including the breakdown of substances like vitamin C and amino acids. Additionally, oxalates can act as antioxidants, helping to protect our cells from damage caused by free radicals. 

While there is no specific daily recommendation for oxalate intake, it is generally advised to consume oxalates in moderation. A balanced diet that includes a variety of foods can help ensure a lower overall intake of oxalates. It is also important to consider individual factors, such as any existing health conditions, when determining appropriate oxalate intake.

For people with conditions like osteoporosis and arthritis, and those prone to kidney stones, managing oxalate intake can be very important.

This blog explores what oxalates are, how they might affect bone density, arthritis and kidney stones, and practical tips for managing their intake.

What are Oxalates?

Oxalates are naturally occurring molecules found in plants, animals, and humans. In plants, they serve as a defence mechanism against predators. In the human body, oxalates can bind with minerals, forming crystals that are excreted in urine or can sometimes form kidney stones. 

Foods High in Oxalates

Oxalates are present in varying degrees in many foods. 

Spinach: Very high in oxalates, with about 750-800 mg per 100 grams when raw.

Rhubarb: Very high, with about 450-650 mg per 100 grams.

Swiss Chard: Very high, with about 500 mg per 100 grams.

Almonds: High, with about 380 mg per 100 grams.

Sesame Seeds: High, with about 330 mg per 100 grams.

Beetroot: About 75 mg per 100 grams.

Sweet Potatoes: About 50 mg per 100 grams.

Chocolate: Cocoa powder contains about 196 mg per 100 grams.

Soy Products: Tofu has about 20-50 mg per 100 grams, depending on processing.

Cabbage and Raw Kale: About 10mg per 100 grams. 

Black Tea: Weak/strong tea contains 9 to 15 mg per cup.

Green Tea: Low, 0.25 mg to 1.2 mg oxalates per cup and Chamomile almost none.

How Oxalates Affect Bone Density, Kidneys and Arthritis

Oxalates can impact bone health primarily by binding with calcium, an essential mineral for bone density, to form calcium oxalate. This binding can happen in the digestive tract, which reduces the amount of calcium available for absorption. For most people, this isn’t a significant problem as they can consume enough calcium to offset this loss. However, in individuals with conditions like osteoporosis or those prone to kidney stones, managing oxalate intake can be crucial.

1. Reduced Calcium Absorption

The main concern with oxalates and bone health is their potential to bind with calcium, decreasing its bioavailability. This is particularly significant because calcium is vital for maintaining bone strength and structure. A diet high in oxalates can potentially lead to lower calcium levels, affecting bone density over time.

2. Risk of Kidney Stones

High levels of oxalates can contribute to the formation of kidney stones, particularly in susceptible individuals. While kidney stones themselves do not directly impact bone density, their presence can indicate that calcium is not being used effectively in the body, which could indirectly influence bone health.

3. Arthritis

Oxalates themselves aren’t directly implicated in causing arthritis, but they may potentially influence the condition, particularly for individuals with specific types of arthritis such as gout or those prone to the formation of calcium oxalate crystals, which can also be associated with other types of crystal-induced arthropathies. 

Oxalate crystals can deposit in joints and soft tissues, leading to a condition often referred to as oxalate arthritis or oxalosis, particularly in individuals with certain underlying health conditions. Oxalate crystal deposition in the joints is rare and usually occurs in the context of broader systemic conditions. If joint problems are suspected to be related to oxalate crystals, a medical evaluation is recommended to confirm the diagnosis and guide treatment.

Here’s how oxalates might impact individuals with arthritis:

1. Crystal Formation: Oxalates can bind with calcium to form calcium oxalate crystals that may deposit in joints, causing inflammation and pain. This is similar to their role in kidney stone formation but can occur in joints, especially in susceptible individuals.
2. Gout Aggravation: While oxalates do not directly cause gout, a high-oxalate diet might worsen the condition by impairing kidney function. This can affect the kidneys’ ability to eliminate uric acid, potentially intensifying gout symptoms.
3. Interference with Mineral Absorption: Oxalates can reduce the availability of crucial minerals like calcium by binding with them, which may negatively impact bone and joint health. This indirect effect can exacerbate arthritis-related joint issues by diminishing necessary nutrients for joint integrity.
4. Secondary Oxalosis: In people with primary or secondary hyperoxaluria, an increased production or ingestion of oxalates leads to high levels of oxalic acid in the body. In primary hyperoxaluria, an inherited disorder, the liver produces too much oxalate. In secondary hyperoxaluria, dietary oxalate intake or gastrointestinal disorders contribute to high oxalate levels. These excess oxalates can accumulate in the joints and other organs.
5. Symptoms and Effects: The symptoms of oxalate crystal deposition in joints include joint stiffness, pain, and swelling, which can mimic other arthritic conditions. Chronic deposition might lead to joint damage or contribute to other complications, depending on the extent of crystal accumulation and the body’s inflammatory response to the crystals.

Managing Oxalate Intake

For most people, it is not necessary to avoid oxalates completely, but those with kidney stones, arthritis, or at risk of osteoporosis might benefit from moderating their intake. Here are some tips to manage oxalate consumption:

• Increase Calcium Intake: Consuming calcium-rich foods during meals can help by binding with oxalates in the stomach and intestines, reducing the formation of calcium oxalate crystals and the amount that reaches the kidneys.
• Stay Hydrated: Drinking plenty of fluids, particularly water, can help reduce the concentration and flush out oxalates before they can form crystals/stones.
• Cook High-Oxalate Foods: Cooking by boiling can dilute the oxalate content in vegetables like spinach and swiss chard by between 30% to 90% depending on the time and the amount of water used, whereas roasting, frying or steaming do not reduce oxalate content.
• Balance Diet: Ensure a balanced intake of nutrients, focusing on low-oxalate and high-calcium foods, and consult with a dietitian if you have concerns about oxalates and bone health.
• Gut Biome: The absorption of oxalates can be influenced by gut bacteria, which can degrade oxalates and reduce their absorption. Variations in gut bacteria among individuals mean some may absorb more oxalates, increasing health risk factors like kidney stones. Probiotic-rich foods like yogurt, kefir, and fermented vegetables, or using probiotic supplements, may help promote a healthier gut microbiome.

Summary

Oxalates in normal dietary amounts are not a health concern for many people, however, if you’re someone who’s prone to kidney stones, arthritis or dealing with low bone density, it’s wise to keep an eye on your oxalate intake.

As with many dietary components, moderation and balance are key. If you have concerns about oxalates and your health, it might be beneficial to discuss them with a dietician or nutritionist. They’re the experts who can help you navigate your diet to ensure you’re getting what you need, while managing what you don’t. 

Stay informed and eat smart to keep your health on track!