The best food for calcium should be milk, because the calcium content of milk is relatively high, containing 104mg of calcium per 100g of milk, and it is relatively easy to absorb. However, the calcium content of some vegetables is comparable or even higher than milk, such as amaranth, mullein, kale, rape, chard, chickweed, spinach, etc. The calcium content is similar to milk, from 66-187mg per 100g, but the absorption rate is lower than milk, because most of the calcium in vegetables is bound calcium that exists in the cell wall of vegetables, and there are oxalic acid, phytic acid and other components that affect calcium absorption. Therefore, the absorption rate may be lower than that of milk. The amount of oxalic acid and phytic acid in vegetables that can hinder the absorption of calcium can be reduced by means of cooking in order to improve the absorption rate of calcium, including blanching vegetables in advance, adding vinegar when cooking, and not putting too much salt, all of which are beneficial to the absorption of calcium.