It really sent me into a spin recently when I read over at Healthy Home Economist that it's best not to eat spinach and silverbeet raw. Whaaat? Why?
Apparently because they contain oxalic acid, which "blocks iron and calcium absorption and may contribute to the formation of kidney stones."
*UPDATED: I was so gutted about this, but then my friend Jessica did some digging and discovered several published studies that have proven it's not so bad eating raw spinach after all. This is especially true if you consume probiotics regularly - in natural yoghurt and kefir.
I'm still not eating as much raw spinach and silverbeet as I used to - we're not including it in our smoothies anymore, but I'm fine to put spinach leaves in salads and on hamburgers.
If you are at all concerned about this, or have a history of kidney stones, oxalic acid can be reduced by a light steam or boil. Tip out the cooking water though, as that's where the oxalic acid ends up.
I had a bit of spare time recently, so I cooked up a big batch of spinach and then a big batch of silverbeet and froze them in ziplock bags to use in lasagne and frittatas in the future. I don't like the taste of cooked spinach much, so I have to disguise it in meals with lots of other ingredients.
1. Bring a big pot of water to the boil.
2. Cut the stalks out of your spinach / silverbeet / kale.
3. Thoroughly wash the leaves.
4. Throw leaves into the pot of boiling water and cook for exactly one minute. (If your water stops boiling when you add the leaves, you can start the timer from when the water starts boiling again. Just watch your leaves to ensure they're not getting overcooked and blackened.)
5. Tip out into a strainer and pour cold water over the cooked spinach until it is completely cool. (This prevents it from over-cooking and turning black.)
6. Squeeze to remove excess water. (For some reason this photo rotates when I upload it, and I can't see a way to rotate it to its correct position. Anyone know what that's about?)
7. Chop up finely. (This helps me disguise it in meals. I've even been known to puree it in the food processor.)
8. Store in the quantities you want in labelled ziplock bags in the freezer until ready to use. (Suck all the air out of the ziplock bags to prevent freezer burn.) (This photo is doing the weird rotate thing too. Any ideas how to fix that in Blogger?)
Whenever I'm making a mince-based dish like lasagne or Asian pork mince, I chuck one of these bags of cooked spinach in it (minus the bag). We hardly notice it's there, but it packs a great nutritional punch.