The Oxalate Problem: Why ‘Healthy’ Foods Could Be Harming You
- Shanda "Panda"
- Feb 5
- 7 min read
Is everyone looking forward to learning chemistry today? I know, I know, probably not most people’s favorite subject (right up there with math). This topic has been at the forefront of my mind recently. I was developing a diet plan for someone who has suspected autism, and this seems to be a huge factor. While I developed a diet plan, I made a whole spreadsheet with over 400 items listed (yes, I’m a nerd at ALL levels). The food list was an eye-opener because a Western diet and even “healthy diets” are FILLED with them.
Who knew spinach, beets, and potatoes could worsen autism and cause heart disease? Let’s dig into oxalates—what they are, what they do, and where they’re found. Of course, the gut microbiome (my favorite) plays a role.
Intro to Oxalates
Let’s first explore what an oxalate is. Oxalates are an anti-nutrient found primarily in plants, most notably spinach. An anti-nutrient is a substance that prevents the absorption of nutrients. Oxalates are an anti-nutrient because they prevent calcium and non-heme-bound iron (iron not from meat) absorption. It does this because it’s a chelator, which means oxalates bind to metals, like calcium. When oxalates bind to calcium, they form hardened crystals. Because it is such a strong chelator, it can bind to other metals (i.e., mercury and lead).
When ingested, oxalates will bind to calcium or iron in the intestines and be eliminated in the stool. Then, calcium and iron can't be absorbed or used by the body (anti-nutrient). If there isn’t enough calcium or metals for the oxalates to bind to, the oxalates will circulate in the bloodstream. Once oxalates enter the bloodstream, problems start to arise.
The kidney’s main function is to filter blood. Kidneys also maintain calcium balance through reabsorption and excretion. The calcium in the kidneys will bind with circulating oxalates, creating kidney stones. The primary reason for kidney stone formation is oxalates. The higher the oxalates, the more likely there is for stone formation [1]. It doesn’t just affect the kidneys, it can build up in the body and cause harm to other areas. The circulating calcium and oxalates can form calcium deposits in the arteries, causing atherosclerosis (narrowed or hardened arteries). From personal experience, I’ve noticed that people with kidney stones often have atherosclerosis. The calcium deposits can also form in the joints, muscles, bones, lungs, sinuses, eyes, and skin. In the joint, it creates calcium deposits creating different types of arthritis.
Oxalates not only cause calcium deposits, but they can also cause inflammation from oxidative stress [2]. Oxalates cause synovitis; inflammation of the lining of the joints (the synovium). Inflammation around the tendons and the bursae (the joint cushion) can also be caused by oxalates. In bones, it can cause fractures, sclerosis, spinal stenosis (narrowing of the spinal canal where the spinal cord is located), and other issues. The nervous system can also be affected, causing problems with the myelin sheath (the layer that protects the nerves) and inflammation of the nerve root [3].
High oxalates have been shown to worsen autism. The children with autism had 3 times the amount of plasma oxalate levels than did the healthy children [4]. I’ll soon write a separate blog post about this later. There is too much about that to cover here.
Research is ongoing about how oxalates affect the body. What I listed is not an exhaustive list of issues related to oxalates. The key takeaway is that it can wreak havoc on the body when high amounts are present.
Where Oxalates Come From
Oxalates come from plants, yeast, and ascorbic acid (vitamin C). Ascorbic acid is a precursor of oxalates. Our bodies convert ascorbic acid (vitamin C) into oxalates. There is no exact figure on how much ascorbic acid is converted into oxalates, but there is a significant increase in urine oxalate when consumption is over 1,000 milligrams [1]. One study found that during the pandemic, people took vitamin C supplements. During that time, there was a dramatic rise in ingestion-associated oxalate nephropathy (kidney disease) [5]. So, stay within the recommended daily amount (RDA) of vitamin C. The RDA is 90mg for men and 75mg for women.
Here's a list of foods high in oxalates:
Spinach
Beets
Teas
Beans
Soy
Most grains
Tumeric
Chia seeds
Almonds and most nuts
Here’s a list of foods that have low or negligible amounts of oxalates:
Apricots
Honeydew
Iceberg lettuce
Unprocessed meats
Dairy
Eggs
Coffee
Coconut
Diets high in oxalates:
Vegan and vegetarian diets
Paleo diets
Western diets
Ketogenic and other low-carb. diets (I think that’s why keto caused kidney stones in studies)
The Gut Connection
The gut microbiome is a large factor in blood and urine oxalate levels. In short, the microbiome acts (and is) a whole ecosystem. There’s a cascading effect when the flora or fauna are out of balance. It’s quite literally the circle of life. For instance, the soil nourishes plants, deer eat the plants, and wolves eat the deer. If there are too many wolves, there are not enough deer, which is catastrophic to the whole system. The same can be true if the soil is imbalanced for the plants or there are too many deer. The microbiome is the same – all in balance. There can be too many “good guys” (deer) or “bad guys” (wolves). Also like any ecosystem, the good ones seem to be the easiest to kill. If there is any microbial imbalance in the gut, it's called dysbiosis.
In a healthy microbiome, some bacteria metabolize (essentially eat and feed on) the oxalates called Oxalobacter formigenes. When the bacteria metabolize oxalates, the oxalates can't go into the bloodstream or cause harm. So, dysbiosis plays a huge role in how much oxalates are absorbed. Oxalobacter formigenes can be bought as a probiotic to help lower oxalates and prevent kidney stones. Research shows that a diet past a certain threshold of oxalates kills Oxalobacter formigenes instead of feeding them. High oxalates can also kill over species of beneficial bacteria [6].
Another gut microbe that plays a role is yeast, known as Candida. It can produce oxalates as a metabolite. The Candida feed on sugars and starches, then expel oxalates as a by-product [7]. Excess oxalate production from Candida is especially true if there is an overgrowth. So, people with Candida overgrowth already have high oxalate levels before eating. A diet high in starch, sugar, and oxalates spells disaster. The other issue is that Candida overgrowth can also be a sign of overall dysbiosis, which means they may also lack Oxalobacter formigenes – a double whammy if not a triple whammy.
A leaky gut can also be an issue since the gut is also a barrier between waste and the bloodstream. It’s like the difference between a coffee filter and a strainer. If you only use a strainer, there will be coffee grounds in the coffee. A leaky gut is like the strainer-- more oxalates will enter the bloodstream. Leaky Gut deserves a separate post, so more on that later. It's just something to be aware of.
The Takeaway
Be aware of how much oxalate is in your diet. Even supplements, such as vitamin C, turmeric (48mg per teaspoon), and chia seeds (45mg per tablespoon), can start to add up. Watching oxalates is especially true if you have kidney disease, arteriosclerosis, or gut issues. While there is no exact figure, the Nephrology Associates consider a low oxalate diet to be less than 50mg per day [8]. I would argue that most people would benefit from that because of the cumulative effects.
Get protein from animal sources and avoid soy. Soy is very high in oxalates and is usually highly processed. Meat, particularly red meat, has heme-bound iron, which makes it bioavailable. The body only absorbs 2% of iron from plants. Red meat also has the most bioavailable vitamin D, B12, selenium, and many antioxidants [9].
Health starts in the gut, so it is also important to maintain or get a healthy gut by avoiding synthetic chemicals. If you already have a healthy gut, fermented foods are a great way to enhance the microbiome. Unfortunately, I can't give the same advice to people with unhealthy guts. It can worsen symptoms and fuel overgrowth. Fermented foods can be an issue because of the histamines.
Did you know that vitamin C supplements could cause such issues? Or that spinach and beets could cause atherosclerosis? Let me know in the comments!
Wishing you good guts!
-Shanda
References:
1. Crivelli, J. J., Wood, K. D., & Assimos, D. G. 2021. Is It Time to Retire the Low-Oxalate Diet? No! Journal of Endourology, 35(10), 1435. https://doi.org/10.1089/end.2021.0576. https://pmc.ncbi.nlm.nih.gov/articles/PMC8575151/#B4.
2. Hawkins-van der Cingel, G., Walsh S. B., Eckardt, K., Knauf, F. 2024. Oxalate Metabolism: From Kidney Stones to Cardiovascular Disease. Mayo Clinic Proceedings. https://doi.org/10.1016/j.mayocp.2024.02.006. https://www.mayoclinicproceedings.org/article/S0025-6196(24)00090-9/fulltext.
3. Lorenz, E. C., Michet, C. J., Milliner, D. S., & Lieske, J. C. 2013. Update on Oxalate Crystal Disease. Current Rheumatology Reports, 15(7), 340. https://doi.org/10.1007/s11926-013-0340-4.
4. Konstantynowicz, J., Porowski, T., Zoch-Zwierz, W., Wasilewska, J., Kadziela-Olech, H., Kulak, W., Owens, S. C., Piotrowska-Jastrzebska, J., & Kaczmarski, M. 2012. A potential pathogenic role of oxalate in autism. European Journal of Paediatric Neurology, 16(5), 485-491. https://doi.org/10.1016/j.ejpn.2011.08.004 https://www.sciencedirect.com/science/article/abs/pii/S1090379811001541.
5. Fong, P., Wusirika, R., Rueda, J., Raphael, K. L., Rehman, S., Stack, M., Gupta, R., Michels, K., Khoury, F. G., Kung, V., & Andeen, N. K. 2022. Increased Rates of Supplement-Associated Oxalate Nephropathy During COVID-19 Pandemic. Kidney International Reports, 7(12), 2608. https://doi.org/10.1016/j.ekir.2022.09.002. https://pmc.ncbi.nlm.nih.gov/articles/PMC9464307/#:~:text=Figure%201.&text=Oxalate%20nephropathy%20with%20(a)%20acute,associated%20with%20gastric%20bypass%20surgery.
6. Suryavanshi, M. V., Bhute, S. S., Jadhav, S. D., Bhatia, M. S., Gune, R. P., & Shouche, Y. S. 2016. Hyperoxaluria leads to dysbiosis and drives selective enrichment of oxalate metabolizing bacterial species in recurrent kidney stone endures. Scientific Reports, 6, 34712. https://doi.org/10.1038/srep34712. https://pmc.ncbi.nlm.nih.gov/articles/PMC5052600/#sec8.
7. Grąz, M. 2024. Role of oxalic acid in fungal and bacterial metabolism and its biotechnological potential. World Journal of Microbiology & Biotechnology, 40(6), 178. https://doi.org/10.1007/s11274-024-03973-5. https://pmc.ncbi.nlm.nih.gov/articles/PMC11045627/#Sec1.
8. Low oxalate diet. Nephrology Associates. https://www.nephrologyonline.com/kidney-disease-dietary-needs-low-oxalate-diet
9. Osaka Metropolitan University. 2023. New antioxidants found in beef, chicken, and pork. ScienceDaily. Retrieved February 4, 2025 from www.sciencedaily.com/releases/2023/02/230217081439.htm
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