The Oxalate Content of a Food Can Mislead: Soluble and Insoluble Fractions
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Effect of Cooking on the Soluble and Insoluble Oxalate Content of Some New Zealand Foods
The difference after cooking is due to losses in preparation, and soluble oxalates are easier to leach. If the person doesn't mind wasting nutrients, boiling the food and discarding the water should reduce the exposure.
But what stands out is how insoluble oxalate predominates in foods, which is harder to absorb and prone to excretion. Taking extra calcium with the meal helps to form the insoluble calcium oxalate.
Calcium oxalate is (molar mass basis):
- 1/3 calcium
- 2/3 oxalate
As the stomach is emptied and the meal alkalinized, oxalic acid becomes charged and can complex with calcium. From the above, to complex with oxalate (and ignoring other interactions), calcium must be present in a solution in at least half of the soluble oxalate content.
- Soluble oxalate (mg) × 1/2 → Calcium (mg)
Even though the absorption of calcium is on average 2/3 of what's ingested, its absorption occurs after pancreatic alkalinization. At that stage of digestion, most of the calcium available in the meal can serve to complex with oxalate and not much is needed. Some calcium is also secreted into the duodenum along with sodium hydrocarbonate.
If a food has 100 mg of soluble oxalate, 50 mg of calcium may be enough to take care of it and can be considered to be wasted. The fraction of absorbable calcium will be the leftover of their reaction.
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Milk with oat meal is always a good idea
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I like to pair oxalate-rich foods with some source of calcium, but depending on the case (if you have recurring problems due to oxalate) it's better to pair with magnesium too, since magnesium oxalate is apparently 100x easier to excrete than calcium oxalate.
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I love oxalates
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Amazoniac always comes through with the most useful information.
I've been wondering whether adding calcium completely negates the value of limiting oxalate intake. Sally Norton says people should keep oxalate intake under 50mg/day which is pretty difficult. I would rather just pair with cheese or chase back some magnesium and calcium if that's an option. Or even maybe cook high oxalate foods in water mixed with some calcium carbonate or citrate.
There's practically no safe food but especially when you limit pufa. It's very frustrating.
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@Amazoniac I wonder if soaking in lye could help similar to how it breaks down starch in corn flour