Bone building is a team effort. Calcium is just one member of the team. Some of the other nutrients may actually be more important since Calcium is now supplied in many fortified foods other than diary, such as orange juice and the many milk alternatives, like almond and rice drinks.
Here is a current reference showing the value of some of those other nutrients, especially magnesium. Some of these other nutrients not only help in the bone building process, but also prevent bone loss which may be just as important as the building process. Another benefit from vitamins like C and B12.
While milk is a rich source of calcium, some other elements in milk must interfere with bone building over the long term. Research shows that milk drinkers have higher risks from fractures. Yes, this is counter to the message from the Dairy Industry. Check out this study.
Another study reveals a very interesting fact. Calcium and vitamin D reduce osteoporosis but do not necessarily reduce fracture risk. Why this difference? The answer probably is connected to the physiology of bones. There are two parts to consider. One is density, the other structure. The marriage or coupling of these two together relates more to fracture prevention than either by themselves. Oh, there is some improvement occasionally in some studies, but simply increasing density while ignoring the building of a stronger structure appears to be the model for mainstream medicine. One that fails most of the time.
For more facts, article.
Below copied from the Harvard Medical website:
"Problems with (Calcium) supplements
Acid rebound. Calcium carbonate may cause acid rebound: the stomach overcompensates for the high dose of calcium carbonate, which is alkaline, by churning out more acid. For that reason, people with a history of stomach ulcers are advised that they may not tolerate it and may have to switch to calcium citrate.
Constipation. Calcium supplements can have a mild binding effect but by themselves don’t usually cause serious constipation. But if you’re taking another supplement or medication that binds the stool, the addition of calcium supplements could cause a problem.
Too much calcium. Although it doesn’t happen often, some people have taken so much calcium that it causes hypercalcemia, an above-normal level of calcium in the blood. Hypercalcemia may cause nausea, vomiting, confusion, and other neurological symptoms.
Drug interactions. Large doses of calcium interfere with the absorption of a variety of drugs. You should avoid consuming large amounts of calcium — either in food or as a supplement — within 2–4 hours of taking a tetracycline or quinolone antibiotic. After taking alendronate (Fosamax), risedronate (Actonel), or another one of the bisphosphonate drugs for osteoporosis, you should wait at least 30 minutes before consuming a large amount of calcium. People taking calcium-channel blockers or beta blockers should discuss taking calcium with their doctors because it can reduce the effectiveness of these drugs."
Sidebar: Also this fact should be mentioned here. Larger calcium intakes, while they might not generate hypercalcemia, they could and probably do interfere with the absorption of other minerals in the same meal. While the body realizes the value of calcium and has a built-in active absorption process for it, any excess over body needs then competes with all the other minerals in a free for all to get absorbed. Excess calcium from sheer numbers often wins out and blocks many of the other major minerals and especially the minor ones. Nature likes balance and even though she has many compensating options available to aid the mineral balance, they use up vital energy and divert elements from other vital body functions.