When discussing plant nutrition, the focus often gravitates toward macronutrients and prominent vitamins or phytonutrients, leaving the less-discussed elements hidden in plain sight.
Unbeknownst to many, one such stealthy component lurking within our meals is the group of compounds known as oxalates. Have you heard of oxalates? These tiny, unassuming compounds hold the potential to wreak metabolic havoc, sparking a cascade of health concerns. Many of you may have read the Men’s Health story about Liam Hemsworth who at the age of 29 developed kidney stones and had surgery for removal after being vegan for four years. His routine included spinach smoothies with almond milk and almond butter just about everyday. There is a strong association here that should not be overlooked. He has since changed his diet.
This article explains the unsettling truth about oxalates and their potential impact on your well-being. Optimal health comes with balance and recognition that not all plants in the plant kingdom are innocent even if we consider them edible.
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What are oxalates?
Oxalates are naturally occurring compounds found in various plants like nuts, leafy greens, fruits and spices. They exist as oxalic acid or oxalate crystals which are both under the broader group of molecules known as organic acids. In plants, oxalates serve various purposes, such as contributing to the plant's defense mechanisms against infections and predators including fungi and insects all while managing calcium stores and capturing sunlight for the plant.
Not so surprising but, oxalic acid is a registered pesticide (parasiticide to be exact) used to control mites in bee-keeping practices. However, oxalic acid is considered “natural” so it is recognized as being safe and organic. Now, don’t be alarmed, using such for honey production does not seem to have any substantial impact on the oxalate load of the honey. We just want to illustrate its diverse applications and potential. Another strong observation recorded in 2006 demonstrated that within a few days after feeding sheep beet greens, which are high in oxalates, the sheep developed anorexia, weight loss, tremors and stumbling.
Unfortunately, oxalates in general are resistant to cooking and digestion. Oxalate crystals are found in the plant and also form in our body (oxalic acid + calcium). These crystals are very abrasive and damaging to our tissues and joints. When you take whole foods like spinach and almonds per say and make smoothies, you are pulverizing the foods and releasing more oxalates from the plant, increasing the toxic burden on your body. Almond milk itself has a high concentration of oxalates.
There is mixed data on oxalate content in foods, and there are many variables like serving size, time the produce was harvested, and even bacteria contamination that can change the oxalate load. However, there are foods that have been tested time and time again and the general trend from highest to lowest oxalate content is shown below.
How do oxalates interfere with our health?
Oxalates can potentially interfere with our health in several ways, particularly when consumed in excessive amounts (not hard to do these days) or for individuals who might be more vulnerable.
- Kidney Stone Formation: One of the most well-known health concerns related to oxalates is their potential role in kidney stone formation. When oxalates combine with calcium in the urine, they can form solid crystals, leading to the development of kidney stones. These stones can be painful and may require medical intervention to treat.
- Calcium Absorption Inhibition: Oxalates can bind to calcium, reducing its absorption in the digestive tract. This can impact calcium availability for bone health and other bodily functions, especially if the diet is high in oxalates and low in calcium.
- Nutrient Binding: Oxalates can also interfere with the absorption of other minerals, such as iron and magnesium, potentially affecting nutrient balance and overall health.
- Gastrointestinal Irritation: In some individuals, particularly those sensitive to oxalates, consuming high-oxalate foods can lead to gastrointestinal discomfort, such as bloating, gas, or abdominal pain.
- Oxalate Sensitivity: Symptoms of oxalate overload can include joint pain (including low back pain), urinary discomfort or nocturia, digestive issues such as IBS-like symptoms or bloating, and neurological symptoms that can resemble dementia or vision changes. People who are more sensitive to oxalates can develop these symptoms even from typical food-level intake.
Eating too many oxalates can cause permanent kidney damage in cases of sustained, very high intake or an underlying condition that increases oxalate absorption. Oxalate crystals that build up in kidney tissue over time can cause a condition called oxalate nephropathy, and the resulting scarring is often permanent, per a review in the American Journal of Kidney Diseases. Typical hyperoxaluria (abnormally high levels of oxalates in the urine) more often causes recurring kidney stones than lasting tissue damage. There are two types of hyperoxaluria:
- Primary Hyperoxaluria: This is a rare genetic disorder caused by a mutation in one of several genes involved in the metabolism of oxalates. As a result of these genetic mutations, the body is unable to properly break down and eliminate oxalates, leading to their accumulation in the urine. Primary hyperoxaluria can range in severity and often requires specialized medical management.
- Secondary Hyperoxaluria: This form of hyperoxaluria is not primarily due to a genetic mutation but is rather a result of other medical conditions or factors. It can occur in individuals with certain gastrointestinal disorders that affect nutrient absorption, such as Crohn's disease or short bowel syndrome. In these cases, the increased absorption of dietary oxalates in the intestine contributes to higher oxalate levels in the urine.
Research indicates that individuals with diminished populations of gut bacteria responsible for oxalate degradation and those affected by specific digestive disorders are more susceptible to elevated oxalate levels within the body.
How is oxalate overload or hyperoxaluria diagnosed?
A 24-hour urine collection that measures total oxalate output is the standard test for diagnosing hyperoxaluria. A doctor typically orders it after reviewing symptoms and stone history, often alongside a blood panel and imaging such as a CT scan or ultrasound to check for existing stones. Genetic testing is added when primary hyperoxaluria is suspected, most often in children or people with a family history of kidney stones.
Warning signs that mean you should see a doctor right away
Fever or chills together with flank pain, an inability to urinate, or pain severe enough that you cannot sit still are warning signs that need immediate medical care. NIDDK also lists persistent vomiting and visible blood in the urine as reasons to be seen right away, since these can signal an infection or a blocked kidney. Milder symptoms, such as occasional discomfort after a high-oxalate meal, warrant a call to your doctor rather than an emergency visit.
Which foods contain oxalates?
| Food | Serving Size | Oxalate Content (mg) per Serving |
| Pumpkin seeds | 1 cup (64g) | <3 |
| Cauliflower (chopped) | 1 cup (107g) | 5 |
| Flaxseed (whole) | 1 cup (168g) | 5 |
| Pecans (halved) | 17 halves (28g) | 18 |
| Clementine (peeled) | 1 (75g) | 20 |
| Hemp hearts | ¼ cup (40g) | 22 |
| Brown rice (cooked) | 1 cup (195g) | 24 |
| Turmeric | ½ tsp (1.1g) | 25 |
| Whole grain bread | 2 slices (75g) | 30 |
| Apricots (dried) | ¼ cup (35g) | 30 |
| Sesame seeds (hulled) | ¼ cup (30g) | 45 |
| Beets (boiled) | ½ cup (85g) | 45 |
| Peanuts (roasted) | 28 nuts (28g) | 45 |
| Walnuts | 100g | 54 |
| Pine nuts (pignoli), raw | 3 tbs (28g) | 60 |
| Black beans (boiled) | ½ cup (90g) | 65 |
| All Bran cereal | ½ cup (30g) | 75 |
| Cashews | 24 nuts (28g) | 75 |
| Cocoa powder | 2 tbs (11g) | 80 |
| Potatoes, Russet, baked, flesh only | 1 medium (170g) | 85 |
| Beet juice | 2/3 cup (160ml) | 95 |
| Chocolate (70% dark) | 1.75oz (50g) | 110 |
| Quinoa (boiled 30 mins) | 1 cup (180g) | 110 |
| Sweet potatoes, baked, flesh only | ½ cup (110g) | 120 |
| Almonds (whole with skins) | 24 nuts (28g) | 120 |
| Chocolate (85% dark) | 1.75oz (50g) | 140 |
| Poppy seeds | 1 tbs (8g) | 180 |
| Buckwheat (cooked) | 1 cup (180g) | 230 |
| Chia seeds | ¼ cup (40g) | 260 |
| Star fruit | 1 (90g) | 270 |
| Beet greens or red stemmed chard, raw | 1 cup (40g) | 380 |
| Spinach | 1½ cup (45g) | 450 |
| Spinach (boiled) | ½ cup (90g) | 450 |
Spinach tops this table at 450 milligrams in a serving smaller than a cup. Liam Hemsworth's daily spinach smoothies, mentioned above, would have added up fast at that concentration.
The fine balance
Maintaining a healthy diet while reducing oxalate intake requires striking a delicate balance. While it's important to manage oxalate consumption, it's equally crucial to ensure that your diet remains well-rounded and nutritious.
A normal and safe level of oxalates for most people would be less than 200 milligrams per day. We can see that it is very easy to exceed this number. Optimal is likely less than 100-150 milligrams. If you are on a low oxalate diet because of a history of kidney stones or pseudogout, it's recommended to reduce that even further to 40–50 milligrams of oxalates daily.
Several pro-tips for reducing oxalates in your diet include:
- Eating a varied diet. Minimize those foods with substantial amounts of oxalates (ones you can reach your daily limit with one serving or less), and focus on incorporating a wide range of low-oxalate options. This way, you can still enjoy the nutritional benefits of various food groups without compromising overall health.
- Opt for nutrient-dense foods that are low in oxalates. Remember foods from animal sources are very low in oxalates and provide many if not all the micro-nutrients the human body needs to thrive. Remember, the brassica or cabbage family of produce like cauliflower, broccoli, arugula and turnips are low in oxalate.
- Watch your portion control. While some high-oxalate foods are nutritious, consider moderating your portion sizes. Smaller quantities of these foods can still contribute to your diet's diversity without causing excessive oxalate intake.
What cancels out oxalates?
Calcium binds oxalate in the digestive tract before either reaches the bloodstream, so eating a calcium source with an oxalate-rich food at the same meal lowers how much oxalate gets absorbed. Mayo Clinic recommends calcium-rich foods at each meal for people managing stone risk, since restricting calcium raises the amount of free oxalate available for absorption. Dairy and fortified plant milks are common calcium sources; a calcium supplement is a separate decision to make with your doctor.
Can You Flush Oxalates Out?
Water dilutes the oxalate already in your urine, which lowers the chance it binds with calcium into a stone, but it does not undo oxalate already absorbed into tissue. NIDDK recommends drinking enough water to keep urine pale yellow, and Mayo Clinic puts a rough target at 8 to 10 ounces of fluid every hour you're awake. Hydration helps prevent new stones from forming. It does not reverse existing oxalate buildup or a diagnosed condition like oxalate nephropathy.
Consulting professionals
As with any dietary component, moderation and a balanced approach are key. If you have specific health concerns or dietary considerations, consulting with a healthcare professional or registered dietitian can provide personalized guidance on managing oxalate intake while still enjoying a nutritious diet.
Our experienced clinicians at Opt Health are here to guide you on your journey to better health. Whether you have specific health conditions or simply want to strike the right balance between reducing oxalates and maintaining a nutritious lifestyle, our experts can provide personalized advice and tailored strategies. Don't navigate this path alone – reach out to Opt Health today and take confident steps toward optimal well-being. Your health matters, and we're here to help you find the harmony your body deserves.
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