Calcium Citrate Vs. Calcium Carbonate Vs. Oyster Shells

While it's possible to get all the nutrients you need from food sources alone, many people find supplements helpful in meeting their daily recommended amounts of certain vitamins and minerals. Many kinds of calcium supplements are available from health food stores and drugstores; calcium citrate and calcium carbonate are two common types. Oyster shell calcium is another name for calcium carbonate.

Calcium Needs

If you're an adult female under 51 years of age or an adult male under 71 years of age, MayoClinic.com notes that you need to get at least 1,000 mg of calcium each day from food or supplement sources. Your needs go up as you age--older men and women need 1,200 mg per day--because your bones decrease in density with time. If you're concerned about getting enough daily calcium from food sources, you have many options for supplements. Calcium carbonate and calcium citrate are both viable options.

Calcium Citrate

One of the common types of calcium available on the market is calcium citrate. You can't find--and don't need--pure elemental calcium. Instead, calcium in your food, in supplements, and in the body occurs as a salt. Calcium salts consist of positively charged calcium particles chemically combined with negatively charged particles. The identity of the calcium salt varies with the identity of the negatively charged particle. In the case of calcium citrate, the negatively charged citrate particles don't have any activity in the body. However, calcium citrate is a well-absorbed source of calcium.

Calcium Carbonate and Oyster Shell Calcium

Calcium carbonate is quite abundant in nature, which is why calcium carbonate pills are typically so much cheaper than calcium citrate pills. One of the most common sources of calcium carbonate for supplementation is oyster shells. Unfortunately, calcium carbonate--whether from oyster shells or from another source--is not particularly well absorbed by the body. As a result, you will not get as much benefit from calcium carbonate as you will from a similar quantity of calcium citrate.

Other Considerations

If you suffer from heartburn, you may be familiar with calcium carbonate for another reason--it's an antacid. Both Tums and Rolaids contain calcium carbonate. The calcium has no effect upon stomach acid, but the carbonate particles react with acid in the stomach. This produces water and carbon dioxide, explain Dr. Reginald Garrett and Dr. Charles Grisham in their book "Biochemistry." You can therefore get some of your daily calcium, in addition to heartburn relief, by using chewable calcium carbonate tablets.