I made the spinach provocation test and I think I can now rule out oxalate (both soluble and insolube/bound to calcium) at least as a stand-alone contributor for symptoms.
I ate a pound of spinach, plain (nothing added), sauteed in a pan without discarding any water, for breakfast with the previous and subsequent meal both being pizza, i.e. high-calcium. I think I felt some symptoms (palpitations) right after the meal, but I think these were nocebo effects or late effects of a previous meal (e.g., pizza contains tomato, which is a nightshade) or because of the high nitrate content. There was no noticable worsening in the next 24 hours.
A pound of spinach contains about 3.5 grams of oxalates which is a dose that vastly exceeds any amount of oxalate a normal meal without high-oxalate foods (spinach, rubarb, chard, beets etc.) would contain. I would probably at some point have to test it again with a protein source (e.g., spinach pasta) and see if it's worse than kale, which contains almost no oxalates, but at this point I am confident that oxalates aren't the problem.
So why did I think oxalates are bad? It's probably because spinach contains other nutrients that do cause symotoms. It is relatively high in protein for a green and also in choline:
https://www.ars.usda.gov/ARSUserFiles/80400525/data/choline/choln02.pdf
So why was spinach lasagna so bad, which brought me to the oxalate hypothesis?
*Contains lots of protein (pasta sheets, spinach, cheese)
*Contains lots of choline in the spinach and pasta, especially if the pasta is whole grain
*Contains lots of fat (olive oil, fat from cheese)
*Lactic acid bacteria from the cheese are introduced during preparation
*It sits around for a good while during preparation and has time to ferment before it goes in the oven and is sterilized
*I used frozen spinach, which is pre-heated and which bacteria can immediately use for fermentation once thawed and frozen spinach probably sits around after blanching for a few hours during production before being frozen
*There is a certain time window in the oven where it gets slowly heated between 30 C and 40 C which provides optimum fermentation conditions for bacteria.
Regarding the last point, there had once been advice by Europe's health authorities that spinach should not be reheated because even that small reheating time would produce too many nitrites:
https://www.independent.co.uk/life-...ng-independent-reader-complaint-a7059316.html
The advice has since been retracted, because they now think this is not a health concern, but the general principle is not in question: Even a few minutes at 30-40 C can lead to significant bacterial degredation activity, which can produce new compounds that weren't present before or wouldn't immediately be produced in the conditions of the stomach. After ingestion, some nutrients would be absorbed quickly and no longer available for the bacteria.
So the spinach lasagna - with its nutrient profile and long preparation and cooking time at moderate temperatures - provided a suitable environment for pre-ingestion bacterial fermentation and activity. I think that was the problem with spinach, not the oxalates.
I ate a pound of spinach, plain (nothing added), sauteed in a pan without discarding any water, for breakfast with the previous and subsequent meal both being pizza, i.e. high-calcium. I think I felt some symptoms (palpitations) right after the meal, but I think these were nocebo effects or late effects of a previous meal (e.g., pizza contains tomato, which is a nightshade) or because of the high nitrate content. There was no noticable worsening in the next 24 hours.
A pound of spinach contains about 3.5 grams of oxalates which is a dose that vastly exceeds any amount of oxalate a normal meal without high-oxalate foods (spinach, rubarb, chard, beets etc.) would contain. I would probably at some point have to test it again with a protein source (e.g., spinach pasta) and see if it's worse than kale, which contains almost no oxalates, but at this point I am confident that oxalates aren't the problem.
So why did I think oxalates are bad? It's probably because spinach contains other nutrients that do cause symotoms. It is relatively high in protein for a green and also in choline:
https://www.ars.usda.gov/ARSUserFiles/80400525/data/choline/choln02.pdf
So why was spinach lasagna so bad, which brought me to the oxalate hypothesis?
*Contains lots of protein (pasta sheets, spinach, cheese)
*Contains lots of choline in the spinach and pasta, especially if the pasta is whole grain
*Contains lots of fat (olive oil, fat from cheese)
*Lactic acid bacteria from the cheese are introduced during preparation
*It sits around for a good while during preparation and has time to ferment before it goes in the oven and is sterilized
*I used frozen spinach, which is pre-heated and which bacteria can immediately use for fermentation once thawed and frozen spinach probably sits around after blanching for a few hours during production before being frozen
*There is a certain time window in the oven where it gets slowly heated between 30 C and 40 C which provides optimum fermentation conditions for bacteria.
Regarding the last point, there had once been advice by Europe's health authorities that spinach should not be reheated because even that small reheating time would produce too many nitrites:
https://www.independent.co.uk/life-...ng-independent-reader-complaint-a7059316.html
The advice has since been retracted, because they now think this is not a health concern, but the general principle is not in question: Even a few minutes at 30-40 C can lead to significant bacterial degredation activity, which can produce new compounds that weren't present before or wouldn't immediately be produced in the conditions of the stomach. After ingestion, some nutrients would be absorbed quickly and no longer available for the bacteria.
So the spinach lasagna - with its nutrient profile and long preparation and cooking time at moderate temperatures - provided a suitable environment for pre-ingestion bacterial fermentation and activity. I think that was the problem with spinach, not the oxalates.