Calcium is another of one of the vital micronutrients our bodies rely on. Not only is it essential for strong bones, but it also is necessary for blood clotting, muscle contraction, regulating heart rhythms, and nerves functions. Most of our calcium, 99%, is stored in our bones. We get our calcium from two sources, food and supplements, and when the body does not get enough from those sources, it begins to draw from the bones. See the problem with not getting enough calcium?
We have been taught that we should get the majority of our calcium from milk and dairy products. However, there are a vast amount of vegetables that also contain calcium and their bioavailability is much higher than dairy. What is bioavailability? It is the amount of calcium that the body is actually able to absorb. Most dairy has a 30% bioavailability, so that means if a cup of milk contains 300 mg of calcium, the amount that the body absorbs is only 100 mg. There are plant foods such as bok choy, broccoli, and cauliflower that have a much higher absorption rate, around 50-60%, so a cup of broccoli has as much calcium as a cup of milk. Spinach on the other hand is rich in many other nutrients but has a very low bioavailability rate, 5%.
As we gain years it is extremely important that we know where our calcium levels are and that we eating a diet rich in calcium, but as we just read, all of our calcium does not have to come from dairy. Post menopausal women need to pay particular attention to their levels because estrogen which is lower at this time also helps calcium absorption, less estrogen less absorption. Those with dairy allergies and intolerances also have to pay close attention to insure they are getting enough calcium in their diet. A list of bioavailability rates can be found here https://americanbonehealth.org/wp-content/uploads/2020/01/12.2B__Calcium_Bioavailability.pdf