I personally eat a fair bit of spinach - I put it in my scrambled eggs, a handful or so, and I throw it in soups for dinner; I also put sorrel in my soup. So I normally eat about two handfuls just about every day. It was recently brought to my attention by my concerned grandma that I am eating too much of the green stuff, and that it contains oxalates and contributes to kidney stones, and joint problems such as arthritis!
Is that true? I've heard that fears about oxalates in greens are overblown unless you have a predisposition to kidney stones. And sorrel schi (a simple traditional Russian soup consisting of bone broth, some vegetables such as cabbage, meat, and sorrel or spinach) has been eaten a LOT in Russia, and as far as I know we never had huge epidemics of kidney stones in rural populations...
Personally, no-one in my family has had them as far as I'm aware, but both my grandparents have stiff joints and accumulation of salts, so I was wondering if I should be eating more Spinach than Popeye could shovel...
What do you think?
Oxalate is an antinutrient and a toxin. It is an antinutrient because in its insoluble form it readily binds with calcium, magnesium, and iron to make oxalate salts (such as calcium oxalate) which are insoluble and usually pass out through your stool. This keeps you from being able to absorb the vital calcium and magnesium. Diets high in oxalate and low in calcium are linked to low bone density. You can either reduce your oxalate consumption (e.g. eat more kale and mustard greens and less spinach) or you can increase your mineral consumption (especially in meals with low oxalate content) to decrease the antinutrient effect.
Oxalate is also toxin when it enters your bloodstream. People with healthy gut function usually only absorb a small portion of this oxalate (2-3%) and don't need to worry about its toxic effect (unless you eat a very high oxalate diet). People with leaky guts or poor balances of intestinal flora, however, can absorb up to 50% of the oxalate in their food and this can cause all kinds of severe symptoms and conditions. I just wrote a post on my blog listing these symptoms and condition (http://lowoxalateinfo.com/who-benefits-from-a-low-oxalate-diet/). Some of the most common symptoms and conditions are burning pain and itching in the genitals, bladder, rectum, mouth, eyes, joints, muscles and skin, and the formation of kidney stones, but other conditions and their link to oxalate are just as important and not as well known (such as autism, allergies and lichen sclerosis). Your body can also make too much oxalate if you take too much vitamin C, you have a genetic defect, or you have a B6 or B1 vitamin deficiency.
If you are a healthy person with a very healthy gut, you might want to consider the antinutrient properties of oxalate or you might just not want to worry about it. If you started a Paleo diet to heal from a leaky gut, you have poor intestinal flora, or you have any of the symptoms or conditions on my list (http://lowoxalateinfo.com/who-benefits-from-a-low-oxalate-diet/), you may want to minimize or eliminate just the highest oxalate foods or you may want to start a low oxalate diet.
I personally have had 15 of the 26 conditions on my list and I have completely healed from 13 of them during my 20 years on the low oxalate diet and I am making great progress on the last two.
Oh! One thing to be careful about -- the internet is FULL of horrible, inaccurate and out-of-date information about the oxalate content of foods. If you want to explore more about the effects of oxalate on your body here are three websites that provide accurate information:
http://lowoxalateinfo.com/ My blog which also has a Paleo/Weston A. Price slant http://www.lowoxalate.info/ This site has a short, accurate list of high and low oxalate foods http://thevpfoundation.org/
In addition, if you want a comprehensive accurate list of the oxalate content of foods (about 190 pages), here's a post I wrote about how to get a free one: http://lowoxalateinfo.com/how-to-get-an-accurate-low-oxalate-food-list/
100 g raw spinach contains 3,900 micromol of soluble oxalate and 3,560 micromol of insoluble oxalate. Forty-seven percent of the soluble oxalate is lost into the cooking water when spinach is boiled for 1 minute, whereas only 10% of the insoluble oxalate is lost.
A study found that in 12 men consuming a 1,970 micromol/day oxalate diet without spinach, fecal oxalate excretion was 1,200 micromol, about 60% of the dietary intake, whereas urinary oxalate excretion was 375 micromol, about 10%; these results imply that 30% (600 micromol) was degraded. During the fourth week of consuming an additional 102 g spinach, which contained about 3,000 micromol added oxalate, fecal oxalate excretion increased to 4,000 micromol--80% of total dietary intake. Again, about 600 micromol oxalate could not be accounted for, which suggests that degradation had occurred.
Another study found that, on average, 68% of a very high intake of oxalate (29,000 micromol oxalate as spinach) was excreted in feces during the last 2 weeks of a 3-week study. However, excretions were very high (near intake) in three subjects but only 10% to 20% of intake in the remaining four subjects. These data suggest that healthy individuals vary widely in their microbial degradation of oxalate.
The majority of dietary oxalate that is excreted in the urine is excreted within 1 to 8 hours after ingestion. Increased excretion is still detectable between 8 and 24 hours after consumption of oxalate-containing meals or loads. Dietary oxalate can be assumed to be absorbed and excreted within 24 hours after ingestion in people with normal gastrointestinal function.
I had four kidney stones when I was 20. I captured the last one (peed into a sieve) and it was analyzed as calcium oxalate. Each of them occurred during or after periods of long-distance travel. The Dr. told me to avoid spinach and chocolate. I did for a while. But I think the contributing factor was more likely dehydration from the travel than overindulgence in chocolate. At that time I certainly wasn't OD'ing on spinach!
I'd say unless you have a history of kidney stones, there's no reason to avoid spinach at all. I eat plenty of it and plenty of chocolate now and I've never had a recurrence. But I am careful to hydrate well, particularly when traveling.
The connection to oxalate consumption is speculative - from what I understand, the two haven't been linked yet. It is, however, true that oxalates can precipitate out some nutrients but if you're eating a diverse diet you won't get enough to care about. Eat varying kinds of leafy greens, drink lots of water, and you don't have to be anal about it. Leeks are also high as are a number of other foods btw in case you need more to worry about :)
I hope this helps others: Oxalobacter Formigenes: The Oxalate Eater. Another cause of high oxalate levels is due to missing bacteria called oxalobacter formigenes. Oxalobacter formigenes is a bacterium (probiotic) found in the gut of most animals. Almost all 6 to 8 year olds have oxalobacter formigenes in their intestines, but only 60 to 80% of adults. Oxalobacter formigenes degrades oxalate by eating it. In fact, oxalate is its only source of food. Unfortunately, it has been shown that oxalobacter formigenes is frequently decreased or missing in people with inflammatory bowel diseases such as celiac disease...............source:http://glutenfreeworks.com/blog/2010/11/17/kidney-stones-renal-calculus-causes-treatment-in-celiac-disease/#.UPrZnGIRbeU................ I did research in local health food store and I wasn't able to find this bacteria. It is a medical shame that the doctors and urologist are hiding this simple solution from us.
I wouldn't worry about it too much. Cooking breaks down some of the oxalate. To cut down the oxalate content even further, you can include vitamin C to your meal - tomatoes are a nice accompaniment, but citrus works too.