Calcium is essential for strong, healthy bones. If there’s not sufficient calcium in the blood (to maintain normal heartbeat, blood coagulation and nerve-muscle function), it will be taken from the bones, which could cause bones to weaken. The requirement is 1,000 mg daily for women up through age 50 and men up through age 70. Women 51 and older and men 71 and older need 1,300 mg calcium daily. And you also need adequate vitamin D so you can properly absorb and use calcium.
Actually, milk, yogurt and many types of cheese are excellent sources of calcium, and they’re also good sources of protein, which is critical for healthy bones. However, overdoing protein by going on a very high protein diet is not healthy. If you’ve heard that it’s better to consume plant sources of calcium than dairy, it could be because some research shows that dairy foods are associated with a higher risk of developing ovarian and prostate cancer. (On the other hand, studies generally show that dairy consumers have lower risk of colon cancer and heart disease.)
The research is not yet definitive on the ovarian and prostate cancer links, but if you’re concerned, or, if you just don’t like dairy, then you can avoid it and still have a healthy diet. (If you’re lactose intolerant, you can usually tolerate Lactaid and other brands of milk that have transformed the milk sugar lactose into its component sugars, which don’t cause intestinal problems.)
If you’re not eating dairy, make sure to get enough calcium through other good sources and/or take a calcium supplement. Sources of well-absorbed calcium include calcium-enriched soymilk and calcium-enriched orange juice. Some plant foods are naturally high in calcium such as collard greens, kale, soybeans, tahini, and spinach, but in general, the calcium in these foods is not very well absorbed by your body. So while these are healthy foods, and do contribute to your calcium needs, don’t rely on them as your sole source.