The TLO Group oxalate spreadsheets list oxalate values for many items in terms of both soluble oxalates and total oxalates. But what is the difference between these two values, and why is it important?
Without going into the chemistry of it, it might be easier to think of “soluble oxalates” as “water-soluble oxalates.” Simply put, soluble oxalates are the oxalate compounds in a food (such as oxalic acid) which are capable of dissolving in water. It might help if you think of it in terms of tea; it’s the soluble compounds in tea (including oxalate, ironically enough) which leach into the water from the tea leaves, and give it a distinctive flavor.
Soluble oxalates are considered to be more bioavailable (more easily absorbed by the gut), and as such more detrimental. And studies have definitely shown that when foods with higher quantities of soluble oxalates are eaten, more oxalates are absorbed (and subsequently excreted – reference here). So for anyone trying to lower the oxalates in a diet, the amount of soluble oxalates in a food is important to know.
Since soluble oxalates can dissolve in water, it is only logical that insoluble oxalates do not. While this may seem like a good thing, it can work against us in some very important ways. For one thing, it means that boiling will not reduce the amount of insoluble oxalate in a given food. And while some sources contend that insoluble oxalates are not absorbed by a healthy gut, many individuals on the low oxalate diet are saddled with a leaky gut. Alas, once the gut becomes leaky, all bets are off; it is entirely possible that both soluble and insoluble oxalates will pass through the membrane of a damaged gut wall.
Of course, even in a healthy gut, insoluble oxalates are acknowledged to cause irritation, as mentioned in this study. Since irritation (and the inflammation it can cause) can contribute to the damage which results in a leaky gut, oxalate itself could conceivably be a cause, or at least a contributing factor, in the development of a leaky gut. This makes it easy to see why a diet that is high in oxalates, such as the Standard American Diet, would be detrimental to overall health. This is also one reason why kidney stones made of calcium oxalate are such a problem; once the calcium oxalate compound has formed, it is no longer soluble in water. So if you’ve already formed the stone, you’re not going to be able to dissolve it no matter how much water you drink.
Why Soluble vs. Insoluble is Important
There are several reasons why one might want to know the amount of soluble vs. insoluble oxalates in a food. For example; a food which has a high level of soluble oxalate might have its oxalate content easily lowered by boiling (although the only way to know for certain is to have the food tested after boiling). In addition, soluble oxalates can tie up dietary (or supplement-sourced) minerals. This is why on the TLO group it is recommended to take calcium with or before meals; the hope is that the calcium will bind the soluble oxalates in the gut, rather than allowing them to be absorbed. Of course, binding them is still no guarantee that they won’t pass through the intestinal wall, but at least if they are already bound to a mineral they will not then be mopping up essential minerals in the bloodstream.
Total Oxalates – The Most Important Number of All
Here’s the most important thing to remember, though: when calculating your daily oxalate intake (or guesstimating, if you prefer that method ), always make sure to use the total oxalate per serving column (when available). Why? Simply put, since we don’t know how much insoluble oxalate is absorbed, and we don’t yet know what its precise effects are on the body, it is always better to err on the side of safety. There have been plenty of reports on the group of folks reacting to foods which have very little soluble oxalate, so chances are quite high that this oxalate is absorbed and affects the body in some way.
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