Low Oxalates Diet
by Sue Kira, Naturopath & Clinical Nutritionist
Oxalates (aka oxalic acid) are naturally occurring substances called organic acids that can be derived directly from the food we eat, or indirectly from our food via the breakdown of amino acids (proteins) as part of our metabolic processing.
Oxalates play a positive role in our metabolic pathways, but when too many accumulate, or if our body doesn’t clear oxalates sufficiently, they can become an issue for us. Some people may develop kidney stones, for others it can contribute to health conditions such as poor gut health, fibromyalgia, or vulvodynia, and have even been linked with some of the signs and symptoms of autism.
Oxalates can also originate from certain fungi such as Penicillium (the fungi that penicillin comes from), Aspergillus and even Candida species has been hypothesised. This means that certain antibiotics or bacterial and fungal infections can contribute to an inability to break down and excrete oxalates.
The good bacteria (Lactobacillus and Bifidobacteria) help us break down oxalates to benefit rather than hinder our bodies. So good levels of these probiotic bacteria are essential for healthy oxalate metabolism.
Rhubarb and chocolate are very high in oxalates. High levels can also be found in spinach, Swiss chard/silver beet, beet greens, peanuts, and cashews. Foods that contain less oxalates but are still quite high in oxalic acid include other dark leafy green vegetables, lemon/lime peel, berries, nuts, legumes, and grains. A list follows.
But it is not only foods that are naturally high in oxalates that can be an issue. Eating too much protein can create problems. This includes nuts, legumes, meats, and eggs. Protein breaks down into amino acids and these aminos can create oxalates as part of the metabolic processes they perform.
For some people, oxalates can be formed by consuming certain types of vitamin C or calcium (particularly calcium ascorbate or calcium oxalate).
Even our red blood cells can make oxalates. Red blood cell membrane fragments (red cells that have been damaged or oxidised) promote the formation of calcium oxalate monohydrate crystal growth and aggregation – also known as the formation of crystals/stones. This is part of the process of oxidation and why antioxidants are so important.
Most people can eat plenty of nutritious high oxalate foods or protein, or take high doses of vitamin C and calcium, with no issues regarding oxalate build-up or poor clearance, whereas others can be quite sensitive to oxalates.
There can be a genetic predisposition towards oxalate build-up or reactions to oxalates. If you have a family or self-history of kidney stones, autism, gut, or behavioural issues, then it may be worth exploring a low oxalate, low protein diet. Also speak to your practitioner about what vitamin C or calcium supplements are most suitable, if needed.
Only 20-40% of our oxalates come directly from our food, but reducing high oxalate foods can make all the difference.
Calcium oxalate kidney stones
When calcium (from food or supplements) is combined with high oxalate foods, calcium oxalate crystals can form. While most oxalates are soluble and can be excreted by the urine or small intestines, the calcium oxalate form is an insoluble type that cannot be excreted as easily or be absorbed for good use.
As the body tries to excrete calcium bound to oxalic acid (calcium oxalate), the formed crystals can block urine flow not to mention create intense pain as the crystals try to pass through the urinary tract. Ouch!
This does not mean you should avoid calcium, but instead a low oxalate diet combined with gut bacterial balance can help to support this problem.
Iron deficiency anaemia
Oxalates can also act as chelating agents, meaning that they bind to other minerals. If they bind to iron they form insoluble iron oxalate which can lead to anaemia. It is because of this binding of minerals to oxalates that vegan or vegetarian sources of iron, such as green leafy vegetables, are not considered good for those with oxalate issues, because while these foods are rich in iron, they are also high in oxalates.
However not all vegetarian/vegan foods are high in oxalates and not everyone has an issue with oxalates. If you are a vegan/vegetarian and find it difficult to keep your iron levels healthy and know you are eating iron rich foods, then oxalates may be part of the problem.
Poor Heavy Metal excretion
Oxalates can also bind to toxic minerals like lead and mercury. This seems good, but unfortunately they then can’t be excreted by the body and can build up in the tissues and organs creating damage.
Autism spectrum disorders
There are many studies that show children with autism have a much higher rate of inflammation in their digestive systems, with many having ‘leaky gut syndrome’. Because of this increase in intestinal permeability, there is a higher risk for excess absorption of oxalates from the diet. This excess travels from the gut into the bloodstream. It’s also common for these children to have an imbalance of bacteria in their gut.
Although more studies need to be done, much anecdotal evidence shows that children on low oxalate diets have improvements in their behaviour, learning ability and concentration, among other positive claims. A low oxalate diet is certainly worth trying, along with considering other health aspects related to the individual.
Oxalate crystals damage other organs and tissues
Oxalate crystals can be very sharp and damage kidneys and the urinary tract. They can also form in and create damage to blood vessels, nerves, brain, joints, bones, and lungs and contribute to associated conditions such as arteriosclerosis, tinnitus, vertigo, lung scarring/cancer, arthritis’s, fibromyalgia, and gout. These crystals can also take the space of bone marrow cells which can affect the immune system. Oxalate crystals can generate a lot of inflammation, oxidation, damage, and pain in the areas that the crystals form.
Other situations that can trigger issues with oxalates
Here are some clinical and personal circumstances that demonstrate how people with no issues with high oxalate foods, can suddenly have problems with them.
- When I was in my teens, I had a boyfriend who went to Bali for a surfing holiday with his mates and when he returned he had an infection in his gut that triggered a case of Ulcerative Colitis (serious inflammatory bowel disease). Not only did the infection require antibiotics, but the decrease of his good bacteria set up a cascade of events that lead to the ensuing bowel disease which required some serious pharmaceutical drugs. These drugs dehydrated his system/kidneys that then lead to kidney stones (dehydration was the reason he was given). The stones or crystals were made of calcium oxalate, (you can get other types, such as uric acid, struvite, or cysteine). He was put onto a low oxalate diet, made to drink heaps of water, and had his meds changed, all of which sorted the kidney side of his health imbalance.
- Other medications have been known to trigger similar situations as above. Some affect the good bacteria in the gut (microbiome) while some affect the liver and its ability to convert minerals and clear toxins. Some meds have terrible side effects which can leave people with all sorts of imbalances that lead to their inability to clear oxalates. The triggering pathway is often unknown. There is so much for science (and all of us) to learn about the interaction of medicines on the body and how different diets can help or make things worse.
- People with Ross River Virus/Fever have been bitten by a mosquito that carries the virus. The virus affects the lymphatic system, including the liver, in such a way that the liver cannot process many minerals as normal. The resulting aches and pains associated with this virus can often be alleviated with a low oxalate diet.
- Similarly, viruses such as Epstein Barr Virus, aka Glandular fever, and other infections like Barmah Forest or Dengue Fever can also benefit from a low oxalate diet.
- Many young clients (kids) I have treated in-clinic over the years have had gut imbalances due to various infections e.g. ear infections, tonsillitis, and subsequent antibiotic use that upset the delicate micro-flora/micro-biome of the digestive system. They then commonly develop ‘leaky gut syndrome’ which creates food intolerances, which then disturbs the liver (among other issues) and they develop a problem clearing oxalates in foods. Often the first thing that parents notice is how their child’s behaviour changes from being ‘such a nice kid’ to a ‘rat bag’ (typical parent’s comments). A low oxalate diet, along with correcting the gut imbalance and healing the leaky gut, has commonly brought back their ‘little angel’.
- I have also seen positive results for those suffering from different arthritis conditions such as osteoarthritis, rheumatoid, psoriatic arthritis, fibromyalgia, and gout. Did you know that there are around 100 different types of arthritis’s and conditions related to arthritis? All can be better supported with a low oxalate diet and by investigating any other drivers of these conditions, such as gut health, food allergies, inflammation, and immune integrity.
Antioxidant Protection from Oxalates
Because oxalates are oxidants, which are free radical damaging molecules, then our body’s own antioxidants (e.g. glutathione) along with antioxidants in the food we eat, can help to protect us from the damage of these substances.
When we have an infection or inflammatory condition then our antioxidant systems may not work as well to protect us. Many low oxalate fruits and vegetables are naturally rich in antioxidants. For more information about antioxidants, see the Antioxidant Rich Diet article.
A low oxalate diet is defined as being less that 50mg of oxalates per day.
Low oxalate foods
The following foods have less than 50mg (0.00176oz) per 100g (3.5oz) of oxalates per serve (unless marked differently).
Note: while the best of care has gone into compiling the following lists, food oxalate content is constantly being revised and updated by the scientific community, so the lists accuracy may change. We will endeavour to adjust as we receive this information. It also appears that certain foods may be fine for some people but not for others, so do take care and only choose foods that feel right for you as an individual.
In children, there is often a natural aversion to certain foods that are not right for them. We adults can feel this too, but often over-ride this feeling with mental rationalisation. You may feel that after eating something, it didn’t feel right, and you can take note of this for next time.
The messages (feeling) from your body are not just about oxalates, but for anything that simply just isn’t right for you, even if it’s just for that specific meal.
Beef, pork, chicken, turkey, fish, seafood, and eggs are all low in oxalates, but proteins break down to amino acids that can create oxalates via metabolic processing so take care with the amount eaten. One palm size of animal protein food per day is considered safe in most cases. By the way, this is the size of the palm of your hand, including the thickness and width (not the size of a palm tree). 🙂
These include – coconut flesh, black-eyed peas, green peas and yellow split peas, flax seeds, lima beans, garbanzo (chickpeas), lentils, pumpkin seeds, and sunflower seeds. All are fine provided you have a maximum of ½ cup in total (cooked or soaked & sprouted) in one day. These beans give you less than 10mg oxalate per ½ cup serve. Other beans like adzuki, baked beans, kidney beans, pinto beans and refried beans contain around 10-25mg per ¼ cup cooked.
- White, wild rice or rice products. Maximum of ½ cup cooked per day
- Corn chips. Only occasionally. Maximum of 1 cup per day
- Fruits such as apples, avocados, bananas, (1 med/day) cherries, cranberries, grapefruit, all melons, passionfruit, mangosteen, lychee, olives, orange juice ½ cup (not the whole fruit), pomegranate, seedless grapes both red and green, peaches, pears, papaya, fresh pineapple, and fresh juice ½ cup (no canned pineapple), fresh strawberries and plums, seedless watermelon (½ cup max per day). Jelly or jam from these fruits is ok in small amounts (1Tbsp)
- Vegetables such as artichokes, asparagus, broccoli, Brussels sprouts, cabbage, cauliflower, cucumbers, endive, kale (¼ cup), lettuce, rocket, Asian greens (½ cup max), mushrooms, onions (yellow and white), peas, radishes, red sweet peppers (capsicum), squash (zucchini, acorn, and yellow – ½ cup day), turnips, mung bean sprouts, string beans, watercress, water chestnuts and pumpkin in small amounts (¼ cup).
- Medium oxalate vegetables: carrots, celery, green beans, fresh corn (¼ cup fine – cornmeal/cornflour & popcorn is low), fennel, parsnips, summer squash, tomatoes and turnips are all medium oxalate vegetables, so keep the quantity down (¼ cup), but have plenty of the above low oxalate vegetables so you still have variety (unless a restriction on an amount is shown).
- Small amounts of white potato (high oxalate) can be tolerated by some. The problem with potato or potato products like chips is that it is usually hard to have only a small amount. However, if the rest of the meal is low oxalate and you have say ¼ steamed potato served with other vegetables, this can be fine unless you are very sensitive, or have kidney stones or pain, in which case it’s just not worth trying.
Fats and Oils
All oils are low in oxalates. Vegetable oils should be not used for cooking at high heat, however they are fine to drizzle over raw or cooked foods. Coconut oil and animal fats are the most heat stable for cooking.
Herbs, Spices and Condiments
Basil, fresh chilli in small amounts, cilantro/coriander, dill, garlic, ginger, nutmeg, onion powder, oregano, fresh parsley (small amounts), salt, saffron, tamarind paste, tarragon, thyme (small amounts), vanilla and white pepper in small amounts. Mayonnaise, mustard, horseradish, apple cider vinegar, coconut aminos, coconut vinegar, coconut teriyaki sauce. Coconut sugar, honey, and maple syrup in small amounts.
Spring and filtered water, apple juice, rooibos and chamomile tea are fine. Tea made from the above herbs and spices in diluted amounts is ok, as is a little honey if desired. Water is best.
Do not drink: mineral water, soda water, soda/soft drinks and juices made from high oxalate fruits or vegetables, alcohol, coffee, drinking chocolate, and black, white, or green tea.
High Oxalate Foods
Foods with more than 50mg of oxalates per 3.5oz/100g per serve unless otherwise noted. Brackets show number of mg of oxalates per serve.
Note: the symbol ~ means approximate
- Beetroot and beet greens (~800mg)
- Spinach – all types (~750mg)
- Swiss chard aka silver-beet (~650mg)
- Rhubarb (~500mg)
- Grains and grain products (up to~250mg), except white & wild rice
- Okra, mustard greens, potatoes, and sweet potatoes (~150mg)
- Figs (fresh or dried) and apricots (dried only) contain (~100mg) per fruit
- Tomatoes canned, tomato paste can have (~100mg) but fresh (~10 to 25mg)
- Blueberries, other berries, and gooseberries (~10 to 100mg). This quantity of oxalates is for a 100g serve so a small amount can be ok
- Kiwi fruit contains around (~100mg) oxalates per fruit
- Orange/lemon peel, (a small amount of fresh juice is ok).
- Mangos, prunes, frozen strawberries (but a small amount when fresh is ok)
- Soy products, especially miso and TVP (but 1Tbsp gluten free soy sauce per day can be ok).
- Beans such as black-beans, navy beans, chilli beans, white beans, pink beans, per ¼ cup (~50 to 100mg)
- Almonds including almond spread, buckwheat (~450mg)
- Cashews, cashew spread, cashew mylk, cashew cheese (~250mg)
- Peanuts and peanut butter (~180mg)
- Other nuts (between ~40 to 450mg). This is per 100g so just a few can be ok e.g. ¼ cup macadamia nuts, peanuts or pistachios only have (~10 to 25mg)
- Potato, potato chips and fries (~65mg)
- Chocolate (~250 to 500mg depending on % cacao)
- Coffee (not so much a high oxalate but dehydrates the kidneys and concentrates oxalates)
- Spices such as turmeric, black pepper, cumin, curry powder, poppy seeds caraway seeds and cinnamon are high in oxalates, but just a sprinkle can be fine to use occasionally.
- Tahini, sesame seeds (sesame oil ok) & chia seeds are high oxalate
Before you commence this diet, see your medical or health care professional for qualified guidance and check if you need extra nutrients from supplements during the diet. Also do not stop any medications or supplements previously prescribed unless advised otherwise by your medical or health care professional.
During the early stages of your new diet, you may experience symptoms such as fatigue, headaches, or body aches, which may occur because your body is detoxifying. However, if you are unsure about a symptom, check immediately with your medical or health care professional.