Why would boiling spinach decrease the iron content?
I've found a lot of articles that say spinach contains more iron when boiled. However, I also came across someone saying the iron content would decrease as the boiling time increases. I was wondering why this is, if someone could answer, that would be great!
Best Answer
So, it turns out people have looked at this, and we can answer with science.
Basically, while the iron content in spinach is high relative to many other vegetables, it isn't very bio-available (i.e. not readily taken up by our bodies). This is because of some compounds found in plants, called polyphenolics. These prevent absorption of the iron by our bodies. So, while iron is at around 2 mg/100g (0.07 oz/3.5 oz) in spinach, the amount we take up is only 1.7% of that amount; 0.044 mg/100g (0.00155 oz/3.5 oz).
There's a handy infographic at compoundchem.com, which shows this:
Now, you didn't ask about that, but to make the answer more useful for other people looking on the same topic, I've included this for background. So, onto the cooking; what effect does that have.
It turns out that in the paper1 (I've linked it here, it may be paywalled and is a PDF, abstract is here), iron is more available after cooking, as you can see from table 2 in the linked paper, where the extractable iron goes up after cooking:
I haven't been able to find out about whether this actually increases the bioavailability of the iron or not (I suspect not), but there is certainly more extractable iron in cooked spinach than uncooked.
1: Yadav SK, Sehgal S. Effect of domestic processing and cooking methods on total, hcl extractable iron and in vitro availability of iron in spinach and amaranth leaves. Nutr Health. 2002;16(2):113-20. doi: 10.1177/026010600201600205. PMID: 12102364.
Pictures about "Why would boiling spinach decrease the iron content?"
Does boiling spinach remove iron?
The leafy green is packed with nutrients, but you'll absorb more calcium and iron if you eat it cooked. The reason: Spinach is loaded with oxalic acid, which blocks the absorption of iron and calcium but breaks down under high temperatures.How does boiling spinach affect iron content?
Oxalic acid naturally binds with minerals like calcium and iron, making them harder for the body to absorb. Cooking spinach can help unlock these iron absorption inhibitors and hence increase iron bioavailability. In other words, cooking spinach helps make iron more available to your body.How does temperature affect iron in spinach?
Fig 1(a) shows the effect of time and temperature of steam blanching on iron content of spinach leaves. Iron content increases with time until 10 min, after what it begins to decrease. It is the same observation with temperature, an increase of iron content until 95\xb0C, and a decrease after this temperature.What does boiling do to spinach?
Blanching the spinach leaves in a large pot of salted hot water quickly wilts the greens in under a minute. This is great for rapidly cooking multiple batches of leaves.Spinach Benefits and Caution Explained By Dr. Berg
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