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Oxalates

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Oxalates, or oxalic acid, are poisonous compounds found in many vegetables. In most cases the amounts are small, but in some cases care should be taken not to consume excessive amounts.

Occurrence[edit]

The highest amounts are found in beet leaves, rhubarb, spinach, beets and chard; purslane and dandelion are similarly high, but are generally eaten in very small amounts so are of less importance. Younger leaves are sometimes reported to have slightly lower levels of oxalate, at least in some plants, but the opposite may also be true.[verification needed][1]

More information:

The problem[edit]

Oxalate can form kidney stones, and can also interfere with the body's absorption of calcium. Caution is especially important for anyone suffering from oxalic acid type kidney stones, or with a particular need for calcium.

Reducing the problem[edit]

Boiling seems to reduce oxalate significantly (by 30-87%)[2] - the water absorbs some of the oxalate and should then be thrown away. Other forms of cooking have little or no impact.

Having a certain kind of bacteria in the gut (Oxalobacter formigenesW) increases the body's tolerance.

Reducing intake is of course the key step for those with existing problems - see #Occurrence, above.

Notes[edit]

  1. WHFoods: Does baby spinach differ nutritionally from mature, large-leafed spinach?: "There had been research showing that baby spinach had lower levels of oxalic acid. Yet, other studies have shown the opposite, that in fact some samples have higher levels."
  2. http://www.ncbi.nlm.nih.gov/pubmed/15826055