What about OXALATES in spinach?

Dear GreenSmoothieGirl: Some people think you should lightly cook your spinach and other greens before eating them. Is it safe to eat them raw?

Answer: This is an excerpt from Ch. 1 of my e-book, 12 Steps to Whole Foods.   It is both safe and good to eat spinach raw, which I have done every day for 15 years. Cooking, by any method, kills 100% of the greens’ enzymes.

A popular and growing theory and opinion among those interested in nutrition is that greens (especially spinach) are high in oxalates and should be avoided because oxalates cause kidney stones or gallbladder problems, since oxalates may interfere with absorption of calcium from the body.   Another popular opinion is that cooking spinach renders the oxalates harmless.

In fact, a review of the peer-reviewed research reveals that the ability of oxalates to lower calcium absorption is small and does not outweigh the ability of those foods to contribute significant calcium to the diet, since spinach is rich in calcium.   A few rare health conditions require oxalate restriction: absorptive hypercalciuria type II, enteric hyperoxaluria, and primary hyperoxaluria.  These are not the more common condition wherein kidney stones are formed.   The research is not clear that restricting foods such as spinach helps prevent stones in those who have previously had them. Many researchers believe that dietary restriction cannot reduce risk of stone formation.   In fact, some foods that were assumed to increase stone formation because of oxalate content (like black tea) have appeared in more recent research to have a preventative effect.

Further, cooking has a small impact (about 10 percent) on the oxalate content of foods, with no statistically significant lowering of oxalates following blanching or boiling of greens.   It appears that the nutritional advantages of eating raw greens continue to far outweigh any benefit of cooking them.

Two other classes of nutritional compounds, purines and goitrogens, are found in some leafy greens such as spinach.   Eating “excessive” amounts of spinach or cruciferous vegetables (broccoli and cauliflower, for instance) containing these compounds can be a problem for people who suffer with gout, kidney stones, or low thyroid hormone production.   These chemical compounds are also found in peanuts, strawberries, soy products, and other foods as well.   Lightly steaming these foods may help, as well.   However, the literature seems to support that a few weekly servings of these foods is a good idea for almost everyone.

10 thoughts on “What about OXALATES in spinach?

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  1. I was always taught that you could only eat spinach (and lettuce) once a week because of nitrates.

    Now I eat a lot more spinach and lettuce than once a week, but it’s always in the back of my mind: am I getting to much nitrates?

    What do you think about this?

  2. Hi Robyn, very interestd in the comment on low thyroid function and spinach. I have low thyroid (hypothyroid) I have been eating spinach every day, in smoothies and salads and thrown into soups. Should I limit my spinach consumption?

  3. The one thing that I thought about when I read the question was the spinach outbreak 2 years ago. Our family was affected so I thought I’d ad a little bit in case anyone who read was concerned on that front.

    If you are worried about food poisoning such as e. coli etc. The truth is that you should wash your spinach but cooking will not help much because you cannot get the spinach to a high enough temp. to kill the e. coli bacteria and have it still be edible. So the short answer is, wash it and hope for the best because unless you like cooked spinach better there’s no reason to do so.

  4. I have an unscientific question regarding spinach.

    A long time ago, my grandfather was a farmer in Missouri. He hated spinach and always said that he wouldn’t eat anything the hogs wouldn’t eat. He proved it by giving them left over spinach (assumed it was cooked) and the hogs would not eat it.

    A couple of years ago, we planted a garden where we lived in Colorado. We planted lettuce, radishes , spinach etc. We fought the animals, the deer, the rabbits etc but we lost, except on the spinach, they just didn’t eat it???? We really enjoyed it!!

    Why do animals not eat spinach? Anyone know?

  5. Anne, the only nitrates you should worry about are the chemical versions in processed meats. Tiffany, I agree. Jeane, interesting–I had no idea!

    Wendy, I have low thyroid function, too, and eat spinach virtually every day–some days LOTS. I can’t advise re: medical issues for any specific situation (don’t know your T-3 and T-2 readings, etc. and am not a doctor), but I just hoped with that passage from the book that people don’t worry about eating natural foods, just because one or two people made a big deal about this oxalate issue. I wanted to put it all in perspective. Fact is, so many other things in greens are nourishing for the thyroid; intuitively, it makes no sense to break down all its parts and say to avoid it as a food because of one tiny part. (The alternatives we might eat if we bump out lots of greens are thyroid suppressing in their own right. Soy isolates? Meat? Sugar?)

  6. I have hyperthyroid and take 3 PTU pills each day to control it. Otherwise I am impossible to be with – too much energy, washing kitchen floor at 3 a.m., talking non stop, flitting from one thing to the other. However, thank goodness, it is all controlled through the PTU medication. I also eat tons of raw green stuff every day, either in green smoothies or salads and feel totally wonderful. Next week am having my annual checkup.

    Thanks for the above info, Robyn.

  7. What about the effects of spinach and other greens on the viscosity of blood? My mother takes coumadin to thin her blood and has to limit her amounts of greens. This is hard on her because she has always been a health nut. She had an arterial blood clot a couple of years ago and was put on meds to thin her blood so she doesn’t have another clot. Now she has to be careful NOT to eat to many salads. Last year I had had a venous blood clot and am not sure if the huge amounts of green make my blood thicker. I DO know that my cholesterol went from 212 to 167 in the last 3 mos and that I have lost 35 lbs. So I certainly dont want to change what is seeming to work.

    I do have a question about my fingernails. They have longitudinal lines down them. I know that it means I am deficient in somthing but I am not sure what. Any ideas?

  8. Anyone taking drugs should follow the warnings of the doctors/pharmacist/drug warning sheet. Coumadin is scary. It’s always frustrating for me to hear that the medical doctors’ protocols not only require all the usual frightening side effects, but also a need to stop or avoid getting good nutrition. That’s rough for your mom.

    Although many theorize that various issues relating to mineral deficiencies show up in fingernails, I don’t about the specific long lines complaint. I’m going to be blogging in the near future about getting whole, completely unrefined salts (with 84 trace minerals) in the diet to address mineral deficiencies–which can’t be overstated as a problem in our culture–and at some point I’ll also talk about iodine. You may want to look at both those issues.

  9. Can you give us some sources for your comment “The research is not clear that restricting foods such as spinach helps prevent stones in those who have previously had them. Many researchers believe that dietary restriction cannot reduce risk of stone formation. In fact, some foods that were assumed to increase stone formation because of oxalate content (like black tea) have appeared in more recent research to have a preventative effect.”

    All I can find is research telling me to avoid these foods. I am sure you have seen those findings as well. (like http://www.ohf.org/docs/Oxalate2008.pdf)

    I want to keep drinking green smoothies and LOVE the hot pink breakfast smoothie but have been feeling more pain in my lower back for the past few months. I want to convince my self to keep going. HELP!

    1. Tiana, read George Mateljan, for one. Oxalates may contribute to stone formation in people who already have some crystallization issues. Overall, it’s a synergistic part of lots of green plants that, with all their other properties, have many preventative effects of course. You would, of course, want to lean on a practitioner for your own very specific health questions.

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