How to obtain the best iron absorption from spinach?

Question

I've heard that while spinach contains plentiful amounts of iron, the iron content is hard for the human body to digest.

Spinach contains oxalic acid that binds with some of the iron, making it harder for your system to absorb.

And also that dietary iron compounds are categorised in two forms: 'heme iron' and 'non-heme iron' and that spinach (in common with many other vegetables) contains non-heme iron. According to this site

Heme iron is typically absorbed at a rate of 7-35%. Non-heme iron is typically absorbed at a rate of 2-20%

Are there ways that I can process spinach in my home so that the iron is easier to digest, or other fruits or vegetables that I could eat at the same time as spinach in order to make it easier to absorb its iron content? For what it's worth, I typically like to consume spinach in curries.

Answer 1

It's not the oxalic acid, it's the calcium:

CONCLUSION: Potassium oxalate did not influence iron absorption in humans from a kale meal and our findings strongly suggest that OA in fruits and vegetables is of minor relevance in iron nutrition. ^source

In short, calcium is extremely digestible in chloridric acid (some people even use it to polish marble), making it harder for iron ions to avoid being bound by another chemical. The truth is that spinach is such a nutrient-packed powerfood that the body struggles to absorb all of them at the same time.

If you are willing to sacrifice calcium absorption in favor of better iron absorption, there are organic acids that preserve it from those bindings. The best choice for a vegan would be, without a doubt, ascorbic acid (also known as vitamin C):

Ascorbic acid (AA), with its reducing and chelating properties, is the most efficient enhancer of non-heme iron absorption when its stability in the food vehicle is ensured. The number of studies investigating the effect of AA on ferrous sulfate absorption far outweighs that of other iron fortificants. The promotion of iron absorption in the presence of AA is more pronounced in meals containing inhibitors of iron absorption. ^source

Just drink a glass of citrus juice.

Answer 2

According to The Vegan Society's iron leaflet

relying on non-heme sources of iron gives the human body control over absorption sufficiency, by allowing it to increase uptake to suit its needs.

So this should not be seen as a problem.

Oxalic acid is broken down by cooking, and, besides being a source of iron

Spinach has a lot to offer nutritionally: it’s an excellent source of folic acid, potassium and magnesium, as well as vitamin K, carotenes, vitamin C and lutein, important for healthy eyes.

Along with The (UK-based) Vegan Society, this article mentions that

the Center for Disease Control and Prevention states that eating spinach with foods that contain a high amount of vitamin C improves the absorption of iron.

Vitamin C is present in a very wide range of fresh fruits and vegetables, but it is destroyed by cooking, so if you want to get some iron from your spinach curry, I recommend either drinking a glass of citrus juice alongside, or, to avoid consuming so much sugar use my number one tip to add vitamin C to a meal: zhuzh a raw red, orange or yellow capsicum pepper in a blender and stir it into your food just before serving. Peppers are one of the best sources of vitamin C, and when raw and blended they pack a great flavour punch too.