Do greens lose calcium from cooking?

Edited Question:

I buy 3 lbs of collards every week (lots of cabbage and broccoli as well). I don’t like them raw, so I steam them for about 15-20 minutes. Is the calcium content of leafy vegetables greatly reduced from cooking/overcooking? Do I overcook my greens? I have no idea about how long I need to steam them. I simply follow the instructions of the steaming machine’s manual. As I don’t wish to lose too much nutrition, can you please tell me if I’m overdoing my greens?


If you compare raw collards to boiled and drained collards at, you will see that they have, respectively, 4.8 and 5.4 mg of calcium per calorie. In this case, cooking the collards miraculously increased their calcium! I think it’s safe to assume this was from variance among batches of collards.

If you compare raw kale to boiled and drained kale, you will see that they have, respectively, 2.7 and 2.6 mg of calcium per calorie.

So, it appears that cooking greens results in only negligible calcium loss, if any.

15-20 minutes seems rather long to cook collards, but steaming can take longer than steeping (which is what I do), so I’m not sure. You could try steaming for 10 minutes to see if that’s long enough.

3 Responses to “Do greens lose calcium from cooking?”

  1. Ariann Says:

    15-20 minutes seems long to cook collards? Collards are traditionally boiled for an hour or more! I love greens, but find collards in particular basically inedible if not boiled for a long time (I drink the “pot liqueur” as well, which is delicious). Since calcium is a mineral rather than a molecule and since there’s no possible nuclear reaction going on during boiling, it seems virtually impossible that calcium would be gained or lost during the cooking process the way vitamins might be, but some of that calcium might be in the cooking liquid.

  2. Anca Says:

    Let’s pretend for a second that cooking greens reduces available calcium. You solve this by undercooking them. But now they’re not very edible or appealing raw. So you eventually give up eating them (and substitute with something with negligible calcium content, for the sake of argument). You’re no longer overcooking your greens (since you’ve given up buying them)…how much calcium are you getting from them now? Moral of the story? Healthy food is only useful if you enjoy eating it.

  3. Betty Says:

    You are absolutely correct, Anca, and you said it very well indeed.

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