<<Disclaimer: Verify this information before applying it to your situation.>> Things I didn't know. From an article in the Aug 14 issue of Newsweek: Women 50 and younger need at least 1000 mg of calcium each day. Calcium carbonate comes from limestone and oyster shells: This is what is used in Tums and most pills. You absorb this best when taken in amounts of 500 mg or less, and it is taken with food and Vit D. Calcium citrate is easier to assimilate and does not need food or Vit D with it. Calcium is depleted when you take a lot of caffeine, protein or sodium. Each gram of protein leaches out 1 to 1.5 mg of calcium; 500 mg of sodium leaches out 10 mg of calcium. Calcium from OJ is an efficient way to get some of your calcium from calcium citrate. If you take 2,500 mg of calcium per day it causes the following problems: constipation, stomach upset; blocks the absorption of critical minerals, especially zinc and iron. If you take extreme amounts of calcium it can harden the kidneys and contribute to the formation of kidney stones. Some research indicates that men with too high a calcium intake are slightly more prone to prostate cancer. Some people who make a practice of eating calcium fortified foods may easily end up with too much. The woman who posed for the Venus di Milo in 150 BC ingested too much calicium: that's how she lost her arms :) -vance