A mineral element that is essential in the diet for building bones and teeth and for many processes in cells.
Sources of calcium from food are mainly milk and other dairy products, sardines, mackerel, and salmon, leafy greens (collard, mustard leaves, kale, bok choy), beans (especially edamame), Tofu made with calcium sulfate, winter squash, wakame (seaweed), broccoli, almonds, sesame and tahini.
Calcium is not easily absorbed by the body, and the amount that is actually absorbed depends on its bioavailability in the food.
Dairy foods have have a high calcium content, their bioavailablity however is only around 30%
absorption, while leafy greens, which genrerally have a lower calcium content than milk, nevertheless have a higher
bioavailability of around 50%. Therefore, eating 1 cup of cooked bok choy has
almost as much bioavailable calcium as 1 cup of milk.
Some plant foods contain oxalates and phytates that bind to
calcium and decrease its bioavailablity. Spinac e.g. which has a high calcium content is also rich in oxalates so that the bioavailability of the calcium is only 5%.
