Oxalates are produced in small amounts as a waste product of human metabolism but occur in very large amounts in some plants. Oxalates occur as a combination of oxalic acid with a mineral such as calcium and can cause pain, kidney stones and other issues over time. Some of the most popular and healthy foods are high in oxalates so we should understand how to deal with them.

Oxalates and plants

In humans oxalic acid is produced as a result of the breakdown of amino acids and is excreted in the urine. Plants make and use oxalic acid in a different way. Oxalic acid is formed as part of photosynthesis to regulate minerals but also as a defence mechanism against predators. Oxalic acid forms to protect from predation like animals, insects, and fungi. Animals that eat too much of it die unpleasantly unless they have well-developed oxalic acid detoxifying systems.

Humans produce 10-30mg per day but we can invest through certain compounds such a spinach several hundreds of miolligrams . You could even ingest a thousands of milligrams of oxalates from a green smoothie!

Approximately 75% of all kidney stones are composed primarily of calcium oxalate. In sensitive people, even small amounts of oxalates cause burning in the eyes, ears, mouth, and throat. Consuming large amounts may cause abdominal pain, muscle weakness, nausea, and diarrhea. People who eat large quantities of raw vegetables may be particularly susceptible.

Symptoms of a high oxalate diet

Symptoms of oxalate poisoning are muscle weakness, burning in the mouth, eyes, ears, nose, and throat, and in the gastrointestinal system, it causes abdominal pain, nausea, vomiting, or diarrhea. Oxalate poisoning does not sound pretty, but you’re unlikely to get acute oxalate poisoning, unless your chronic (daily) consumption of oxalates is so high that your body fails to clear it. When oxalates bind to calcium in your blood, tiny, sharp oxalic acid crystals form and can be deposited anywhere in the body and cause muscle pain. When this happens in the kidneys, it causes kidney stones.

Kale and other cruciferous vegetables like broccoli, cabbage, cauliflower, etc. can block production of thyroid hormones and inhibit iodine into the thyroid gland, which slows the production of thyroid hormones.

Thyroid hormones such as T3 and T4 play an incredibly important roll in regulating your metabolism. If thyroid production slows down, your metabolism slows down, and your fat burning ability slows way down. Goitrogens are no joke. Reducing the amount of uncooked cruciferous vegetables (i.e. kale) you eat will reduce the amount of goitrogens you let in your body. But there is a safe way to get the good stuff from kale. Read on…

Foods high in Oxalate

Unfortunately high sources of oxalate are some very popular and keto friendly foods. From highest to lowest, – buckwheat, black pepper, parsley, poppy seed, rhubarb, amaranth, spinach, chard, beets, chocolate, most nuts, most berries, and beans.

Nine types of raw and cooked vegetables were analyzed for oxalate using an enzymatic method. There was a high proportion of water-soluble oxalate in most of the tested raw vegetables.

The flip side

With some green vegetables in focus in this article, it’s also important to acknowledge steamed veggies provides a wealth of vitamins to support good health and performance.Green veggies like kale have a high concentrations of antioxidant vitamins A, C, and K. Just one cup of chopped steam kale contains 885 mcg of vitamin A. It also helps protect against infection from pathogenic organisms. The vitamin C found in kale facilitates tissue repair, boosts the immune system, and provides antioxidant protection against pathogens and toxins. Kale is also incredibly rich in vitamin K and suppr a wide variety of bodily functions, including normal blood clotting, antioxidant activity, and bone health.Because veggies like kale contain an abundance of health and performance optimizing vitamins, you should keep them in your diet but only if you take action against its built-in problems.

How to cook high oxalate foods

Like phytates, oxalates can be reduced by cooking and draining the water, or by soaking in acid. Added dietary magnesium and zinc bind to oxalic acid, thus lowering oxalate absorption substantially.

Boiling / Steaming

Boiling markedly reduced soluble oxalate content by 30-87% and was more effective than steaming (5-53%). An assessment of the oxalate content of cooking water used for boiling and steaming revealed an approximately 100% recovery of oxalate losses. The losses of insoluble oxalate during cooking varied greatly, ranging from 0 to 74%. Because soluble sources of oxalate appear to be better absorbed than insoluble sources, employing cooking methods that significantly reduce soluble oxalate may be an effective strategy for decreasing oxaluria in individuals predisposed to the development of kidney stones.

Boiling your vegetables will cause the oxalate to “leach” out of them. Leaching is the extraction of certain materials from a carrier (in this case, your vegetable) into a liquid (the boiling water). A study of this process found that boiling fresh New Zealand grown spinach reduced the amount of soluble oxalate by more than 60%. (Plants carry both soluble and insoluble oxalate; it’s generally harder to reduce insoluble oxalate.) Another study looked at a wider range of vegetables and found that soluble oxalate was noticeably reduced in most of them after boiling.

To leach your leafy greens, you can boil them in water for about 6-10 minutes, depending on the type of green. Once you have boiled and drained your greens, be sure to season them to taste with some spices, like garlic or mustard.

Your beloved spinach and kale green smoothies may be causing more harm than good. Oxalic acid is an antinutrient compound found in many plants, like raw cruciferous vegetables — kale, radishes, cauliflower, broccoli — as well as chard, spinach, parsley, beets, black pepper, chocolate, nuts, berries and beans.

Dinosaur Kale

Also, steaming your vegetables will protect your thyroid and ensure that you get all the nutrients provides – like vitamins A, C, and K.

Oxalic acid crystals can form anywhere in your body when oxalic acid binds to calcium to form crystals, causing muscle pain. It’s very similar to the way uric acid crystals form in joints in cases of gout. I suspect that many people with diagnosed gout, especially at a young age, also have oxalic acid problems. Oxalic acid also causes most kidney stones when it binds to calcium in the kidney. Low-grade fungal infections happen quite often in relatively healthy people, and they increase your oxalic acid burden.

Eat Veggies with Fat for Optimal Absorption of Vitamins

Many vitamins and micronutrients are fat-soluble, meaning they are not well absorbed without the presence of adequate fat. One study showed that people who consume salads with fat-free salad dressing absorbed far less of the helpful phytonutrients and vitamins from spinach, lettuce, tomatoes, and carrots than those who consumed their salads with salad dressing containing fat.

Calcium Loading

Because oxalic acid binds vital minerals in the gut, long-term consumption of foods high in oxalic acid can lead to nutrient deficiencies. When calcium supplements are taken with foods high in oxalic acid, the oxalic acid actually precipitates in the gut and drastically reduces the levels of oxalate absorbed by the body. Some cases show as much as a 97% decrease in oxalate levels.Additionally, a 1997 study showed that “mineral water containing calcium and magnesium deserves to be considered as a possible therapeutic or prophylactic agent in calcium oxalate kidney stone disease”. The best way to calcium load is not to take pills or drink water, but to toss your calcium carbonate and magnesium oxide supplements in the blender with your kale. Let the harmful oxalic acid precipitate out in the blender, so your body can filter it out when you drink it. If you allow free oxalic acid into your body without minerals at the exact same time, it will absorb into your body, then, depending on your genetics, infections, history, and your oxalate load, it can form crystals in your muscle tissue and/or kidneys.

Lightly steaming cruciferous vegetables for up to 30 minutes (far less helps) also significantly reduces the amount of goitrogens. In the same way lightly cooking vegetables also helps break down the cellular structures to increase the digestibility and nutrient absorption of nutrients in the vegetables. Nutrient absorption is also important in terms of the amount of energy your body is actually getting from the food you eat.

Key Takeaways

  • Oxalic acid is something you should minimize no matter where it comes from.
  • Never add raw kale, spinach, or chard to salads or smoothies. Steam them first, drain them , add some fat, lemon/vinegar and some cheese.

Further Reading

  1. http://www.westonaprice.org/food-features/the-role-of-oxalates-in-autism-and-chronic-disorders
  2. http://www.ncbi.nlm.nih.gov/pubmed/9096270
  3. What are Goitrogens and How Do they Affect the Thyroid
  4. http://www.ncbi.nlm.nih.gov/pubmed/20361352 – Role of dietary iodine and cruciferous vegetables in thyroid cancer: a countrywide case-control study in New Caledonia.
  5. https://www.urologyofva.net/articles/category/healthy-living/3740469/the-damaging-effects-of-oxalates-on-the-human-body
  6. https://pubmed.ncbi.nlm.nih.gov/15826055/