Just taking calcium isn't the answer. Matter of fact, just calcium alone can be deadly. Here's why--
Calcium can build up in body areas other than bone. This is called calcification. It can deposit in joints, kidney (stones), breast, lung, arteries (atherosclerosis), tendons and other soft tissue.
We're told to take calcium with vitamin D and magnesium. Calcium and magnesium work together with collagen and other minerals to build bone matrix. But calcium is actually hard to absorb. That's the reason for the vitamin D--it helps your gut absorb calcium. So, ideally, when calcium is absorbed, we hope it goes to build bone. But that's not always the case.
Enter vitamin K2. It's only in the last few years that vitamin K2 is being discussed, because little was known about it. Vitamin apparently K2 interacts with a protein in the body that directs calcium into the bones and teeth where it belongs.
So, where do we get it? Beef, butter, eggs. Wait, there's a problem! Actually, two problems. For forty years or so we've been (wrongly) told to avoid those things because saturated fat causes high cholesterol and heart disease. And, yeah, the other catch is that the beef and chickens have to be raised in the pasture, exposed to sunlight and have their natural diet instead of the corn and grains they are being fed now. Grass-fed beef (100%) and pastured eggs. Hard to find and expensive.
The only known plant source for K2 is a fermented soybean product the Japanese eat with rice. It's called natto. The K2 isn't formed from the soybeans; it's formed from the bacteria on the soybeans. It's sticky, slimy and stinky and not even relatively available. But it's also cultured and dried for supplements. So, that's probably the only reliable source for us right now.
K2 comes in different forms, but primarily MK4 and MK7 are what we need for bone health. It is debated which form is best, so I got a supplement with both forms in it. By the way, this all started with me when I got a coronary artery calcium (CAC) scan that showed I had a calcium score of 234, which isn't good. So, I'm trying to stop the progression before this eventually completely blocks my artery.
I really have a very long and arduous rant I could give, because there is much more to the story, including how our food supply is adulterated, how the pharmaceutical companies manipulate information to our detriment, and how uninformed the medical community is about lots of things including nutrition. But I won't. There are many pieces of the puzzle to put together, and I'm beginning to see a picture emerge that's not apparent without a lot of digging.
Just, if you want strong bones, and particularly if you take calcium (which I don't and never have), please get magnesium (citrate or glycinate preferably), vitamin D3 AND don't forget the K2.