Oxalates isn’t a word that comes up much in casual conversation, but these naturally occurring compounds, contained in many plants, can have a major role in chronic disease, inflammation, and more.
Many people suffering from digestive issues, kidney stones, interstitial cystitis, and autoimmune disease are asking: are oxalates (or oxalic acid) bad for you? Furthermore, it’s important to know the risk factors for oxalate issues, and what foods are best for those avoiding them.
A low oxalate diet can be beneficial for many patients, reducing symptoms of chronic, inflammatory, and autoimmune diseases — and, conceivably, autism. So, what are oxalates, and how do you know if a low oxalate diet is right for you?
Oxalates: What are they? How are they processed?
These organic acids can be found in many plants and plant-based products that can be a part of other “healthy” diets. Oxalic acid has the ability to combine with minerals such as calcium, sodium, magnesium, and potassium to form compounds generally referred to as oxalate salts. An example of an oxalate salt would be calcium oxalate.
High oxalate levels may be a byproduct of your body digesting foods high in vitamin C. However, you may be consuming foods from plants that have the ability to make their own oxalates.
An unbalanced microbiome may also be to blame, as certain gut bacteria like Oxalobacter formigenes can assist in regulating and removing oxalate buildup. (Balancing your gut takes more than probiotics — read more). Molds, particularly Aspergillus, and yeast can also produce oxalates, contributing further to the overall oxalate burden in your body.
Most people can expel about 90% of the oxalates in their body through stool or urinary oxalate excretion. However, some people are not equipped to purge oxalates, and instead continue to accumulate them over time, causing a variety of health issues down the line. These include calcium oxalate kidney stones (the most common variety), malabsorption, and more.
How Oxalates Interfere with Nutrient Absorption
Most people aren’t sensitive to oxalates. Unlike some other “antinutrients,” oxalates are often found in vegetables and other healthy foods. It’s important to incorporate medical advice into your decision to adopt a low oxalate decision, since they aren’t a problem for everyone.
In fact, most oxalate-rich foods are also full of antioxidants, minerals, and other nutrients. Cutting these out can have harmful effects, so be sure to take a researched and measured approach as you consider this diet.
However, for those who struggle with oxalate buildup, these molecules can actually interfere with nutrient absorption. Since oxalates are reactive, they have a tendency to attach to minerals in the gut and keep them from being absorbed.
For example, spinach, which has a high amount of calcium and oxalate, stops calcium from being absorbed. Another study found that fiber and oxalates have a similar interaction, blocking the nutrients from proper use. This same study saw drops in levels of zinc, magnesium, and calcium after one week on a high-oxalate diet.
For those with an oxalate sensitivity, this compound could not only be putting you at risk for other issues, but also preventing you from absorbing and using necessary nutrients. So, how do you know if an oxalate restriction is right for you?
Who should follow a low-oxalate diet?
People with specific conditions or environmental factors may benefit from this change. Here’s who should cut down on their oxalate intake.
Patients With Hyperoxaluria or Hypercalciuria
These rare conditions result in chronic kidney and bladder stones, caused by an overproduction or heightened absorption of oxalates. At its most drastic state, it can even lead to end-stage renal disease, preventing the kidneys from properly filtering waste and fluids.
Since these conditions are a result of high oxalate concentrations in the body, it’s recommended that those with hyperoxaluria and hypercalciuria avoid oxalates.
Those With Kidney Stones
Calcium oxalate stones, the most common type of kidney stones, are painful incidents caused by too much oxalate in the body. Patients who have had at least one kidney stone are advised to lower oxalate consumption in order to avoid becoming repeat stone formers.
Experts also recommend eating more foods high in calcium in order to prevent future stones.
Children At Risk For ASD
Science may reveal a potential link between oxalates and the development of autism spectrum disorder. Children with autism may display impaired kidney function, making it harder to process oxalates.
Also, since the gut bacteria of children with ASD is less diverse, these patients may not have the necessary good bacteria needed to balance oxalate levels.
Antibiotic Users
Remember O. formigenes, the bacteria that regulates oxalate buildup? Well, it actually feeds off of oxalates and dramatically reduces the buildup of this molecule in the body. Unfortunately, antibiotics can wipe out this strain of bacteria in the gut, leaving you unprotected.
Those with a prolonged history of antibiotic use may need to reduce oxalates as the microbiome rebalances.
Patients With Leaky Gut
As previously mentioned, an overabundance of oxalates can interfere with nutrient absorption.
Leaky gut, a condition that also impacts the gut’s ability to intake nutrients, can compound on these effects. For this reason, it’s wise to steer clear of oxalates if you’re suffering from dysbiosis or leaky gut, and supplement with probiotics.
Foods High in Oxalates
A diet with a consistently high intake of oxalate and low calcium is not recommended for anyone. However, there are even more symptoms caused by certain foods in those who can’t process these compounds properly.
An individual eating high-oxalate foods can develop many of the health risks listed above. Here are some common foods with high levels of oxalate:
- Beets (and beet greens)
- Kiwi
- Collard greens
- Cocoa powder
- Okra
- Wheat bran and shredded cereals
- Raspberries
- Stevia sweeteners
- Sweet potatoes
- Soy and soy milk
- Chocolate
- Leeks
- Spinach
- Swiss chard
- Rhubarb
- Cashews, peanuts, and almonds (and nut butters)
- Green beans
These are just a few of the foods to avoid. For a more complete list, as well as further information on oxalates and what foods are friendly to this diet, you can read more here.
Because of the high amount of oxalate in many plant foods, vegetarians may be more likely to develop kidney stones than others. However the intake of calcium and magnesium may modulate the intestinal absorption of dietary oxalate, by binding to oxalate in the gut, thereby limiting the intestinal oxalate absorption and urinary oxalate excretion.
Cooking to Decrease Oxalate Content
Interestingly, many “healthy foods” are higher in oxalates than more processed foods, which can be confusing when trying to eat a more plant-based diet. So, how does one decrease oxalate content in foods while still getting the necessary nutrients? The answer: cooking.
Cooking raw vegetables can decrease their oxalate content by up to 87%. Especially through boiling, it’s possible to still enjoy and benefit from many vegetables that would otherwise be off-limits.
In Summary
- Oxalates are compounds that can form kidney stones. They are often a byproduct of too many oxalates ingested from food, or a mold/yeast overgrowth, or a lack of healthy gut bacteria.
- Though not everyone will struggle to break down this compound, those who are sensitive may suffer from nutrient malabsorption, inflammation, or kidney stones as a result of too much oxalate.
- Patients with hyperoxaluria or hypercalciuria, kidney stones, leaky gut syndrome, heavy antibiotic users, and children diagnosed with or at risk for ASD are advised to follow a low oxalate diet.
- While many vegetables, nuts, and plant products are high in oxalate, the amount they contain can often be lowered through cooking.
- For certain people with oxalate regulation issues, a low-oxalate diet can potentially reduce the risk of kidney stones, improve nutrient absorption, lower inflammation, and decrease the symptoms of many health conditions.
Before starting a low oxalate diet, it’s best to seek medical advice. If you need a functional medicine doctor who is familiar with oxalates and how it relates to health in the Kansas City area, book an appointment with Jellison Integrative MD, or call 913-568-0608.
Sources
- Traxer, O., Huet, B., Poindexter, J., Pak, C. Y., & Pearle, M. S. (2003). Effect of ascorbic acid consumption on urinary stone risk factors. The Journal of urology, 170(2), 397-401. Abstract: https://www.ncbi.nlm.nih.gov/pubmed/12853784
- Oda, M., Saraya, T., Wakayama, M., Shibuya, K., Ogawa, Y., Inui, T., … & Ota, T. (2013). Calcium oxalate crystal deposition in a patient with Aspergilloma due to Aspergillus niger. Journal of thoracic disease, 5(4), E174. Full Text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3755682/pdf/jtd-05-04-E174.pdf
- Siener, R., Bangen, U., Sidhu, H., Hönow, R., Von Unruh, G., & Hesse, A. (2013). The role of Oxalobacter formigenes colonization in calcium oxalate stone disease. Kidney international, 83(6), 1144-1149. Abstract: https://www.ncbi.nlm.nih.gov/pubmed/23536130
- Heaney, R. P., & Weaver, C. M. (1989). Oxalate: effect on calcium absorbability. The American journal of clinical nutrition, 50(4), 830-832. Abstract: https://www.ncbi.nlm.nih.gov/pubmed/2801588
- Kelsay, J. L., & Prather, E. S. (1983). Mineral balances of human subjects consuming spinach in a low-fiber diet and in a diet containing fruits and vegetables. The American journal of clinical nutrition, 38(1), 12-19. Abstract: https://www.ncbi.nlm.nih.gov/pubmed/6305185
- Cochat, P., & Rumsby, G. (2013). Primary hyperoxaluria. New England Journal of Medicine, 369(7), 649-658. Abstracti: https://ghr.nlm.nih.gov/condition/primary-hyperoxaluria
- Worcester, E. M., & Coe, F. L. (2010). Calcium kidney stones. New England Journal of Medicine, 363(10), 954-963. Full text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3192488/
- Gul, Z., & Monga, M. (2014). Medical and dietary therapy for kidney stone prevention. Korean journal of urology, 55(12), 775-779. Full text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4265710/
- Sorensen, M. D. (2014). Calcium intake and urinary stone disease. Translational andrology and urology, 3(3), 235. Full text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4708574/
- Konstantynowicz, J., Porowski, T., Zoch-Zwierz, W., Wasilewska, J., Kadziela-Olech, H., Kulak, W., … & Kaczmarski, M. (2012). A potential pathogenic role of oxalate in autism. european journal of paediatric neurology, 16(5), 485-491. Abstract: https://www.ncbi.nlm.nih.gov/pubmed/21911305
- Waring, R. H., & Klovrza, L. V. (2000). Sulphur metabolism in autism. Journal of nutritional & environmental medicine, 10(1), 25-32. Full text: https://search.proquest.com/openview/fc4a7ba41170dcdad64a34275d4557a3/1?pq-origsite=gscholar&cbl=33383
- Li, Q., Han, Y., Dy, A. B. C., & Hagerman, R. J. (2017). The gut microbiota and autism spectrum disorders. Frontiers in cellular neuroscience, 11, 120. Full text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5408485/
- Kaufman, D. W., Kelly, J. P., Curhan, G. C., Anderson, T. E., Dretler, S. P., Preminger, G. M., & Cave, D. R. (2008). Oxalobacter formigenes may reduce the risk of calcium oxalate kidney stones. Journal of the American Society of Nephrology, 19(6), 1197-1203. Full text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2396938/
- Mittal, R. D., Kumar, R., Bid, H. K., & Mittal, B. (2005). Effect of antibiotics on Oxalobacter formigenes colonization of human gastrointestinal tract. Journal of endourology, 19(1), 102-106. Abstract: https://www.ncbi.nlm.nih.gov/pubmed/15735393
- Liebman, M., & Al-Wahsh, I. A. (2011). Probiotics and other key determinants of dietary oxalate absorption. Advances in Nutrition, 2(3), 254-260.Full text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3090165/
- Bsc, S. N., & Bsc, G. S. (1999). Oxalate content of foods and its effect on humans. Asia Pacific journal of clinical nutrition, 8(1), 64-74. Abstract: https://www.ncbi.nlm.nih.gov/pubmed/24393738
- Chai, W., & Liebman, M. (2005). Effect of different cooking methods on vegetable oxalate content. Journal of agricultural and food chemistry, 53(8), 3027-3030. Abstract: https://pubag.nal.usda.gov/catalog/1367062
Taylor, E. N., & Curhan, G. C. (2007). Oxalate intake and the risk for nephrolithiasis. Journal of the American Society of Nephrology, 18(7), 2198-2204. Full Text: https://jasn.asnjournals.org/content/18/7/2198
