1. http://zqb.cyol.com/content/2009-04/01/content_2604811.htm
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Posted by faunablues on Nov 24, 2010 · Member since Aug 2003 · 9655 posts
regarding oxalates, spinach does have them. but spinach also has calcium, which is why spinach isn't as great of a source of calcium as it appears to be. calcium with oxalate actually appears to decrease oxalate absorption in the GI tract, as stated here:
http://www.springerlink.com/content/l5xh217202326110/
but regardless, there is not so large an amount of oxalates in spinach that it sequesters calcium from other foods. some greens (like taro leaf) have higher levels of oxalate, and if consumed raw, is fairly toxic. but spinach is relatively low.
the calcium oxalate kidney stones depend on calcium & oxalic acid filtration in the kidney; in other words, both of these substances have to be in your bloodstream. If you're not absorbing oxalic acid (or not a whole lot of it), then it won't be coming out through the kidneys. Also, calcium oxalate stones tend to form in an acidic urine. Plant-based diets tend to yield more alkaline urine because of the different protein composition (I think that's why?) versus animal foods. So, everything else being equal, a vegan will have a urine that is more alkaline than an omnivore, and be less disposed to forming oxalate stones. I think that there was a organization (american urological society or something. or nephrology, i forget) that recommended reduced dietary animal protein to prevent kidney stones (as well as less salt, more water, etc).
