The body allows for absorption of only about 20-30% of ingested calcium. Recommended dosages of 1300 mg/day for 9-18 years of age, 1000-1200 mg/day for persons 19-50 years of age, and 1500 mg for persons over 50. The standard dose recommendation is that of 1200 mg/day for most adults. (men and women).
Foods that contain a higher level of calcium such as broccoli, chinese cabbage, milk, yogurt, sardines, soy nuts, dried figs, greens (kale, mustard, & turnip), cheese, and fortified orange juice.
You would need to consume 3 cups of any dairy products a day to achieve the daily recommended dose of 1200 mg/day.
Foods that affect the absorption of calcium include caffeine, chocolates, spinach, liver, and raisins to name a few.
Calcium supplements should be taken in 500 mg or less a day with meals for better absorption. Calcium carbonate is usually the easiest to digest.
Calcium absorbs better with meals because their absorption is increased with an acidic environment.
Also, if already taking a mutivitamin that contains Vitamin D, it is best to purchase a calcium supplement that does not contain Vitamin D. Do increase dietary fiber and water intake to avoid the problems with constipation, one of the major side effects of calcium supplements.
Along with building bone density is exercise. Exercise is a great way to build stronger bones and density. Bones become more thick and stronger with exercise so help promote strength and the prevention of falls.
an excellent article that talks about calcium supplements is http://www.medscape.com/viewarticle/548054
Since 2000 there have been several studies on the effects of calcium and bone density associated with osteoporosis. Many state that calcium supplementation is not effective in protecting from falls/fractures while several studies site the effects of calcium and its effects on protection.
The key to many of these studies is that what they have found is that people were inconsistent in taking calcium supplements faithfully day in and day out.
There are many many calcium supplements out there on the market in todays society. Read the labels to find the product that is best for you. Taking larger doses impairs the absorption so keep in mind that although you may take a supplement 3-4 times a day rather than once or twice, you will benefit from taking it more often than not since it is much easier to absorb with meals, and breaks down easier with the smaller doses.