Avoid Oxalates… or Process Them? A Clue from the Andes

If you’ve heard me speak for more than five minutes, there is a very good chance you’ve heard me talk about oxalates. I have personally struggled with health issues related to oxalate toxicity in the past, and I firmly believe this is a rapidly growing issue affecting modern health on a global scale.

For years I’ve been bringing them up in classes, lectures, and conversations about food, diet, and health because they are one of the many compounds found in plants that can interfere with mineral absorption and contribute to kidney stones and an array of other metabolic challenges.

Bill teaching about oxalates in Norway

Until recently, oxalates were rarely discussed outside of specific medical contexts. But that seems to be changing thanks to pioneers like Sally Norton. Even in the popular media we are finally starting to hear more about oxalates and the potential challenges they present in foods like spinach, rhubarb, beet greens, almonds, sweet potatoes, and many other plants.

One solution that is often proposed is simple: avoid foods high in oxalates.

But whenever I hear that recommendation, my mind immediately goes somewhere else.

I start asking a different question:

How did traditional cultures deal with them?

---

Bill doing research in Bolivia with ntives harvesting oca.

Because when you look closely at the foods people have eaten for thousands of years, you quickly realize something important. Humans did not simply avoid plants that contained compounds that could cause problems. Instead, they developed processing techniques that transformed those plants into safer, more nourishing foods.

This idea has guided much of my research for years. I have spent a great deal of time studying ancestral detoxification techniques - things like cassava fermentation, acorn leaching, and nixtamalization - where traditional processing unlocks nutrients and removes compounds that would otherwise make a food difficult or dangerous to eat.

So naturally, when I first began learning about oxalates, I started searching for ancestral detoxification strategies that specifically deal with them.

And for a long time, I came up empty.

Despite digging through ethnographic accounts and scientific literature, I could not find clear examples of traditional food processing techniques that consistently removed oxalates in a meaningful way. Cooking and boiling are often suggested, but the evidence for their effectiveness is surprisingly limited and inconsistent.

A recent conversation may have opened a new door.

I recently had a fantastic conversation with a scientist at the New York Botanical Garden who pointed me toward a dissertation examining the traditional processing of oca (Oxalis tuberosa), a tuber crop cultivated for centuries in the Andes.

In some Andean communities, oca is processed into a traditional food called khaya. The process involves soaking the tubers in water and then repeatedly exposing them to freezing night temperatures and warm daytime sun - essentially a natural freeze - thaw and drying cycle that takes place over several days.

What caught my attention was a remarkable observation in that research.

When the scientist analyzed the final processed khaya product, no oxalates were detected in the finished food. And, this from a plant whose genus is Oxalis!

That finding immediately caught my attention.

I want to emphasize that this research is still in its early stages, and I don’t want to get anyone too excited just yet. But it prompted me to start digging deeper, looking for patterns in traditional food processing that might help explain what is happening.

And what I have begun to uncover is something fascinating.

Across cultures and continents, humans repeatedly developed a small set of techniques to deal with compounds in plants that would otherwise make them difficult to eat.

Oca (Oxalis tuberosa), a tuber crop cultivated for centuries in the Andes

---

Soluble vs. Insoluble Oxalates

Not all oxalates behave the same way.

Plants contain two primary forms:

• Soluble oxalates, which dissolve in water and can be absorbed by the body.

• Insoluble oxalates, which are bound to minerals like calcium and largely pass through the digestive system.

The soluble form tends to raise the greatest concern because it can bind minerals and, in some cases, contribute to kidney stone formation.

But there is an important detail here that may explain why traditional processing methods matter so much.

Soluble oxalates dissolve in water.

Which means that processes involving soaking, fermentation, or other forms of leaching may help reduce them in plant tissues.

---

A Pattern That Shows Up Everywhere

When you begin looking at traditional food cultures through this lens, a fascinating pattern appears.

Across the world, humans developed a handful of recurring strategies for dealing with plant compounds that could otherwise make foods difficult to eat.

Soaking and Leaching

Many traditional food systems rely on soaking plant foods in water to remove soluble compounds. This technique appears in foods as diverse as cassava in the Amazon, acorns in North America, and taro in the Pacific. The soaking step in khaya processing may function in a similar way.

Fermentation

Fermentation is another powerful ancestral tool. Microbes can break down compounds that interfere with digestion or mineral absorption. In some cases, microbes may even contribute to the breakdown of oxalate molecules themselves.

Freeze - Thaw Processing

The khaya process introduces a particularly fascinating mechanism. Freeze–thaw cycles rupture plant cells, releasing their contents and potentially allowing compounds like oxalates to be more easily washed away during soaking.

This same natural freeze-drying technology appears in another famous Andean food: chuño, the freeze-dried potatoes that have nourished high-altitude communities for centuries.

Pairing Foods Wisely

Traditional food cultures also often pair high-oxalate foods with calcium-rich ingredients. Calcium can bind oxalate in the digestive tract, forming insoluble calcium oxalate that passes through the body rather than being absorbed.

Examples of these pairings appear in cuisines around the world—from greens cooked with dairy to tubers served with creamy sauces or coconut milk.

---

The Gut Microbiome Piece

There is another piece of this story that makes things even more interesting.

Certain bacteria in the human gut - most notably Oxalobacter formigenes - can actually use oxalate as a food source.

In other words, some microbes consume oxalate as part of their metabolism.

This suggests that human physiology, traditional diets, and microbial ecology may have been working together for thousands of years. Diets rich in fermented foods and diverse plant ingredients may have helped support microbial communities capable of handling compounds like oxalates far more effectively than many modern diets do today.

---

Looking Back to Move Forward

What I am beginning to see is something that fits a much broader pattern in the history of human food.

For thousands of years, people did not simply avoid plants that contained toxins or anti-nutrients. Instead, they developed processing technologies that allowed them to safely access the nutrition those plants offered.

• We fermented cassava.

• We leached acorns.

• We nixtamalized maize.

• We freeze-dried potatoes.

And perhaps, in the Andes, communities also developed processing techniques that helped deal with oxalates in plants like oca.

These ancestral food technologies were not accidents. They were sophisticated cultural innovations developed through generations of observation, experimentation, and shared knowledge.

This research is still in its early stages, but it highlights something that I have come to believe again and again:

Sometimes the best place to look for solutions to modern nutritional challenges is in the food traditions of the past.

Processing in Bolivia

If you’re interested in learning more about the traditional food processing techniques that shaped human diets - from fermentation to nixtamalization to nose-to-tail cooking - explore the classes and research happening through Modern Stone Age and grab a seat at the Ancestral Table!

These ancestral skills are not just historical curiosities. They may hold some of the most important insights for navigating modern nutrition!

---

Reference

Bradbury, E. Jane. 2014. Investigating the Effects of Domestication on Crop Toxicity: Analyses in Manioc (Manihot esculenta) and Oca (Oxalis tuberosa). PhD Dissertation, University of Wisconsin–Madison.