The message from the Dairy Industry of the United States and the U.S. Department of Agriculture is simple. Calcium intake through milk consumption helps to prevent osteoporosis. However, many experts are still divided on the actual merits of milk as a primary source of calcium. The advertising makes a person think that they must drink milk to be healthy. What is actually undisputed is that calcium is important in preventing osteoporosis, and milk is a good source of calcium. If you like milk, drink it. If you don't, there are other sources of calcium.
The body is quite efficient at absorbing calcium levels up to 500 mg, but becomes less efficient for amounts above that. Women who take calcium supplements after a calcium rich meal may not absorb as much as they think.
The best advice is to eat a calcium rich source at every meal and if supplements are used, the supplement could serve as the calcium rich source for that meal.
Calcium absorption is most efficient at 500mg or less. As calcium intake goes, about 500mg at a time the percentage of extra calcium you absorb drops dramatically. Research has shown this. The National Academy of Sciences set calcium requirements for the United States in 1997 as 1000mg a day if you are under fifty and 1,200mg a day at 50+.
Do not make the mistake of assuming that if you take 1000mg of calcium at one meal you are absorbing enough for the whole day. The best advice is to divide your calcium intake over the course of the day.
It is uncertain whether it is more beneficial to take a calcium supplement at bedtime. Parathyroid hormone levels seem to be highest in the blood at night and some feel that taking calcium make parathyroid hormone levels drop, therefore protecting the bone.