What is a Low Oxalate Diet?
People who follow a low oxalate diet are striving to reduce consumption of high oxalate foods. Some also avoid salt and/or calcium rich foods. The goal is to consume no more than 40-50 mg of oxalates in a given day. A normal diet contains about 150 mg per day.
The reason a person may wish to try this type of diet is to reduce a chronic problem with kidney stones or a build-up of oxalate crystals elsewhere in the body such as the thyroid. About 10% of the population is genetically predisposed to their formation.
However, there is an environmental component as well. Those who have taken a lot of antibiotics and/or suffer from imbalanced gut flora also may experience health issues from consuming too many oxalates on a daily basis.
What are Oxalates
Oxalates and oxalic acid are naturally occuring chemicals. They are found in a wide variety of plant foods, from dark leafy greens, nuts and seeds, to many fruits and root crops! They are found in very low to nonexistent amounts in animal foods like dairy, meat and eggs. Thus, vegans and to a lesser extent, vegetarians find reducing sources of oxalic acid in the diet quite hard to do.
In addition, our body produces them. The liver manufactures oxalates under certain low enzyme conditions. Thus, it is not fully accurate to classify oxalates as anti-nutrients. While researchers haven’t sorted out what role(s) this group of chemicals play, it is clear that like many in our food and body, it has both benefits and risks.
Avoiding high oxalate foods is the quickest way to relief according to some doctors and health gurus. Many of these foods are nourishing and ancestral in origin. Why would we need to avoid these traditional foods? Isn’t there another way to prevent or resolve a problem with excessive buildup of oxalates in the body?
Does a low oxalate diet even work or offer other health benefits? Before we consider these questions, let’s take a look at what foods are high in oxalates. When you see how long it is, you might wonder if perhaps these foods are a problem because of what we have done to our bodies, especially our guts, and not because of the oxalates themselves.
High and Low Oxalate Foods
While most high oxalate foods follow a clear pattern, a few may surprise you!
Foods considered to be high oxalate contain between 10 and 50 milligrams per serving. As mentioned before, high oxalate foods are plant based. Hence, those espousing a plant based diet are most at risk from the health issues that can occur from overconsuming them.
Note that the fruits, vegetables, nuts, seeds, legumes and grains listed in the charts below are those that are highest in oxalates. If you don’t see a whole food you are looking for, it most likely contains low to no oxalates on a per serving basis. For example, wheat is very high in oxalates on a per cup basis. However, the average person would not consume an excessive amount per serving as ground flour in a baked good. For this reason, it is not listed.
Note that for processed foods purchased at the store, the oxalate levels can vary considerably depending on the manufacturer. Sticking to freshly prepared dishes allows for more accurate tracking of oxalate intake on a daily basis.
High Oxalate Fruits (Fresh)
The list below identifies fresh fruits that are very high, high, or moderate in oxalates. All other fruits have little to none. Note that canned and dried fruits may contain high levels whereas the fresh fruit counterpart is low.
Pineapple is a good example of this. While a cup of fresh pineapple is very low in oxalates at 2 mg per half cup, the same amount of canned pineapple is very high at 24 mg and dried pineapple is even higher at 30 mg. However, other foods like apples and pears are low oxalate fruits in either fresh or canned/dried form. Similarly, high oxalate food like nuts are also high in processed forms such as almond flour or meal.
Hence, if you are oxalate sensitive, do not automatically assume that if a food is low oxalate in fresh form, the same is true for processed forms and vice versa. There is clearly some negative aspects to industrialized fruit processing that have the potential to add these substances.
|Avocados||1 fruit||Very High||19mg|
|Dates||1 date||Very High||24mg|
|Grapefruit||1/2 fruit||Very High||12mg|
|Kiwi||1 fruit||Very High||16mg|
|Orange||1 fruit||Very High||29mg|
|Raspberries||1 cup||Very High||48mg|
|Tangerine||1 fruit||High||10 mg|
|Figs||1 med||Moderate||9 mg|
High Oxalate Vegetables
The chart below lists all the high oxalate vegetables and legumes. There are a number of other moderately high vegetables. The University of Chicago provides an excellent and very comprehensive list if you wish to dig deeper. The worst offenders are noted in red.
Spinach whether cooked or raw is the highest of all foods in oxalates. It follows that the dangers of green smoothies containing large amounts of this vegetable are potentially quite considerable.
|Bamboo Shoots||1 cup||Very High||35mg|
|Beets||1/2 cup||Very High||76mg|
|Fava Beans||1/2 cup||Very High||20mg|
|Navy Beans||1/2 cup||Very High||76mg|
|Okra||1/2 cup||Very High||57mg|
|Olives||approx 10||Very High||18mg|
|Parsnip||1/2 cup||Very High||15mg|
|Red Kidney Beans||1/2 cup||Very High||15mg|
|Refried Beans||1/2 cup||Very High||16mg|
|Rhubarb||1/2 cup||Very High||541mg|
|Rutabaga||1/2 cup mashed||Very High||31mg|
|Spinach, cooked||1/2 cup||Very High||755mg|
|Spinach, raw||1 cup||Very High||656mg|
|Tomato Sauce||1/2 cup||Very High||17mg|
|Turnip||1/2 cup mashed||Very High||30mg|
|Yams||1/2 cup, cubed||Very High||40mg|
|Carrots, raw||1/2 lg carrot||Very High||15 mg|
|Celery, Cooked||1 cup||High||10mg|
|Soybeans||1 cup||Very High||96mg|
|Brussel Sprouts||1/2 cup frozen||Very High||17mg|
|Celery, raw||1/2 Cup||Very High||19mg|
|Potato||Med, baked||Very High||60 mg|
|Sweet potatoes||4 oz cooked||Very High||141 mg|
Oxalates in Nuts and Other Common Foods
The list below identifies other common high oxalate foods on a per serving basis. Again, the worst offenders are noted in red.
|Almonds||1 oz||Very High||122mg|
|Cashews||1 oz||Very High||49mg|
|Peanuts||1 oz||Very High||27mg|
|Pistachios||1 oz||Very High||14mg|
|Walnuts||1 oz||Very High||31mg|
|Sesame Seeds||1 oz||Very High||26 mg|
|Soy Milk||1 cup||Very High||20 mg|
|Miso||1 cup||Very High||40 mg|
|Tea (brewed)||1 cup||Very High||14 mg|
|Cocoa Powder||1 tsp||Very High||17 mg|
|Tofu||3.5 oz||High||13 mg|
|Soy Protein Isolate||1 oz||Very High||27 mg|
|Amaranth||1/2 cup||Very High||115 mg|
|Buckwheat Groats||1 cup||Very High||133 mg|
Note a number of surprises. Kale is not listed because it is low in oxalates, for instance. Sweet potatoes, raspberries, and a number of other foods are high!
Also note, while some foods are very high in oxalates – like black pepper – the amount people consume is quite small. So the actual amount of oxalates someone gets from such foods is miniscule and not of much concern.
Furthermore, with some high oxalate foods – like raspberries – the amount you may absorb is quite small. This is because the bulk of the oxalates are in the small seeds that our bodies don’t actually fully digest. So some high oxalate foods may in fact be only moderate or low oxalate in practice.
Low Oxalate vs Kidney Stone Diet
While a low oxalate diet may help prevent kidney stones in some people, it is not the same as a kidney stone diet.
A kidney stone diet is even more restrictive than a low oxalate diet as it seeks to restrict the intake of calcium rich foods as well. This would most notably include all types of dairy foods.
Oxalates and Kidney Stones
Do oxalates really cause kidney stones or oxalate crystals to build up in other body tissues? The answer is not really. In certain people, higher oxalate consumption can lead to these painful health challenges. However, it isn’t what really causes them. Let’s take a look at this complex issue.
First, if you are genetically or otherwise prone to kidney stones (about 10% of the population), you are at a higher risk. Kidney stone formers are different from the rest of us. (2)
Second, it appears that repeated exposure to antibiotics contributes to this issue and even possibly causes it in some people.
Certain beneficial strains of gut flora, specifically oxalobacter, break down oxalates! These strains are destroyed by antibiotics and potentially dozens of other pharmaceuticals. They are not commonly included in probiotic supplements. (3)
According to the American Society for Microbiology:
Oxalate degradation by the anaerobic bacterium Oxalobacter formigenes is important for human health, helping to prevent hyperoxaluria and disorders such as the development of kidney stones. Oxalate-degrading activity cannot be detected in the gut flora of some individuals, possibly because Oxalobacter is susceptible to commonly used antimicrobials. Here, clarithromycin, doxycycline, and some other antibiotics inhibited oxalate degradation by two human strains of O. formigenes. (4)
How Low Oxalate Diets Can Backfire
It is important for those considering a low oxalate or kidney stone diet to understand that the potential exists for making the problem worse. This is because diets low in oxalates can cause beneficial gut microorganisms that break these substances down to die off from lack of food! Over time, a person could become even more sensitive to the effects of oxalates. (5)
In addition, an imbalanced gut typically has an overgrowth of yeast. Oxalates are produced in large amounts by fungus! Large oxalate containing stones have been found in the sinuses and lungs of people suffering from systemic fungal infections such as Candida or Aspergillus.
The lack of proper gut bacteria is is why fecal transplants help some people with kidney stone issues. This procedure helps replenish and rebuild the beneficial bacteria that deal with excess oxalates in the body. (6, 7)
The same goes for the kidney stone diet. Low calcium intake as recommended by certain health authorities can actually contribute rather than resolve a propensity to form kidney stones.
Other Factors Affecting Kidney Stones
Other factors that affect a problem with stones forming in the kidneys include excessive vitamin C and high protein intake. Collagen supplementation, especially for those who are B6 deficient, is also a concern according to Chris Masterjohn PhD:
Oxalates can cause problems in a variety of ways when they’re elevated in the blood, but it’s far more common for them to be elevated in the urine where they will contribute to kidney stones because oxalate binds to calcium to form calcium oxalate crystals. Now glycine can be converted to oxalate, but this is not a major fate of glycine. However in gelatin and collagen you have another amino acid, hydroxyproline. Oxalate can be a major fate of hydroxyproline and in fact gelatin supplements and presumably collagen supplements by extension, gelatin supplements have been shown to increase the urinary excretion of oxalate at fairly low doses that we’ve been talking about in these videos and can even increase the blood oxalate concentrations if the dose is really large such as 30 grams of gelatin. (8)
Does a Low Oxalate Diet Work?
Is it worth it to consider a low oxalate diet if you are prone to kidney stones or have a diagnosed issue with oxalate shards embedded in other tissues? Unfortunately, the answer is not a solid yes. While such a diet can be helpful, the extent of the benefits is not as cut and dry as sufferers might hope.
As mentioned above, there are many contributing factors. Oxalate intake is only one part of the picture. Also, many foods that are moderate or high in oxalates are incredibly healthy. Collagen, vitamin C, protein – limiting these has its own risks and drawbacks. This is especially true with limiting protein. While it may help those with kidney stone issues, it contributes to other, even more significant problems.
Tips for Preventing Kidney Stones
So what should you do? According to Chris Masterjohn Phd, “Ideally you want to focus on the protective factors so that you can increase your ability to tolerate the potentially harmful factors.” (8)
Protective factors first include getting sufficient natural dietary calcium! Too little natural calcium from whole foods actually contributes to issues with oxalates. Aim for at least 100-1200mg/day.
Third, consume a diet rich in potassium and take mineral supplements in citrate form. Last, avoid processed foods! The reason is that processed foods often contain phosphate additives that are hidden and not listed on the label. These substances can aggravate the risk of kidney stones. (8)
Using these tips combined with avoiding only the highest oxalate containing foods may be the most sensible approach of all.
The best way to know what works for you is to test your urine pH and oxalate levels. pH is something you can track at home using pH test strips. You want a urine pH between 6.4 and 6.8.
DIY Remedy to Help Kidney Stones
By the way, there is one interesting and somewhat all natural way to help prevent and remove kidney stones – roller coasters! While researchers have developed an ultra-sonic or similar device to break up kidney stones, using it has risks and side effects (10). A safer DIY kidney stone treatment is simply going to your local theme park a few times a month!
How does this work? It appears that the bumping and jostling on a roller coaster may break up larger stones. In addition, it apparently helps smaller ones make their way out of the body before they get too large. (11, 12)
Score another one for older, bumpier, wooden roller coasters and similar rides!
Sarah Pope has been a Health and Nutrition Educator since 2002. Her work is dedicated to helping families effectively incorporate the principles of ancestral diets within the modern household. She is a sought after lecturer around the world for conferences, summits, and podcasts.
Her work has been covered by major media including USA Today, ABC, NBC, and many others.