>The following are adequate and sufficient calcium substitutes:
>- dark greens: broccoli, spinach, collards, kale, turnips, bok choy,
>parsley, mustard, dandelion
Not a vegan, LOVE dairy products (Kefir! YUMMY!), but here <http://www.vrg.org/nutrition/calcium.htm> Disclaimer: Don't get your manties in a wad. Dietary/nutrition information is always tentative. We may learn tomorrow that everything they're starting to learn about calcium absorption is wrong or has been blown out of proportion -- like some of the horseshit shoveled about cholesterol and fat. Oh, and that they are now shoveling about low-carb. If I see one more "Try our low-carb menu" sign, I'm going to beat it with my lezbean phallus.
Anyway, calcium combines with other substances. Sometimes the binding aids absorption making it more bioavailable; other binding hinders absorption making it less bioavailable. Vita min D and magnesium, for instance, aid the absorption of calcium. I thought lactose did, too, but I didn't bother to look it up...
Vegetables and grains typically contain substances that hinder calcium absorption. Oxalic acid (oxalate) in spinach, for instance, binds with calcium and prevents 95% of it from being absorbed. Similarly, calcium binds with phytic acid in wheat bran and the phosphates in brown rice, make it unavailable.
Besides which, even if the calcium were completely bioavailable, you'd have to eat 10 c. of spinach a day. Or 3 cups of nuts. Or 6 cups of bok choy. Or some combination. (I once calculated all this to see if I could actually afford to get all my micronutrients from food! I couldn't!)
Calcium is
49-61% bioavailable in low oxalate veggies such as bok choy, broccoli, Napa cabbage, collards, kale, okra, turnip greens.
31-32% bioavailbe in calcium-set tofu and OJ with added calcium.
21-24% bioavailable in red beans, white beans, soy milk, almonds, sesame seeds.
If you pop a supplement, then the best is calcium citrate, then calcium carbonate (40% bioavail)