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Thread: Oxalates in leafy greens

  1. #1
    Join Date
    Dec 2006
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    Abbotsford, BC
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    Default Oxalates in leafy greens

    I know leafy greens are not a major food source of tegus, so this topic might be more suitable in an iguana forum, but I thought I'd post it here anyway because I know some of you, myself included, use leafy greens as part of your tegu's diet. A source of concern when using leafy greens is their oxalate content and the resulting limitation in calcium absorption when oxalates and calcium meet in the gut.

    Since oxalate ions have a -2 charge and calcium ions have a +2 charge, one ion of oxalate would bind to one ion of calcium to form one calcium-oxalate molecule. Because of this relationship, if we know the amount of oxalate ions and calcium ions in a given amount of, say, spinach or collard greens, we can figure out if there is a surplus of either calcium or oxalate ions. The surplus will be absorbed into the blood while the calcium-oxalate molecules will pass through in the feces. The passing of calcium-oxalates in the feces is not a problem, we are more concerned with what is absorbed into the blood. Calcium absorbed into the blood is good, this is available for use, while oxalates absorbed into the blood is bad, this will bind with blood calcium but will be deposited and will collect somewhere in the body, it will not pass through in the feces. So having calcium bind with oxalates in the gut is fairly harmless, while having them bind in the blood is bad.

    You can prevent oxalates from being absorbed into the blood by making sure there is enough calcium to at least bind all the oxalates in the gut. So you can come up with a ratio of calcium ions to oxalate ions for different foods (a ratio of calcium to oxalates in grams or milligrams doesn't work, these values need to be converted to actual ions). I came up with such ratios for a few commonly used greens:

    Ca ions : Ox ions
    1 : 5.70 (swiss chard)
    1 : 4.40 (spinach)
    1 : 0.15 (collards)
    1 : 0.06 (kale)
    1 : 0.06 (dandelion greens)

    Any ratio in which the oxalates outnumber the calcium indicates a oxalate surplus, if the calcium outnumbers the oxalates, there is a calcium surplus.

    So spinach and swiss chard give an oxalate surplus, oxalates will be absorbed into the blood and can bind with blood calcium. Bad.
    Collards, kale, and dandelion greens give a calcium surplus, calcium will be absorbed in the blood. Good.

    Spinach and swiss chard can be used, but should be supplemented with calcium to bring the ratio in favor of calcium. Collards, kale, and dandelion don't need supplementation.

    For tegus, really they should receive most of their minerals (calcium included) through whole animal prey so this info is more important for more herbivorous reptiles, but does still apply to tegus.

    If anyone has anything to add, has any conflicting information, or wants more information, please post.
    Last edited by dpjm; 02-14-2014 at 06:00 PM.

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