Organic calcium is calcium derived from plant sources such as algae, in comparison to calcium derived from limestone or other mineral sources. Though technically calcium is an inorganic mineral regardless of its source, calcium supplements are based on compounds of calcium, not the pure element. In this regard, ordinary limestone-derived calcium is, in fact, calcium carbonate, and organic calcium is usually calcium phosphate or calcium citrate.
Calcium supplements that are labeled as organic calcium are often in the form of calcium chelates. A chelate is an organic compound with hydrogen bonds that is bound to a metallic ion such as calcium. Though calcium is not often thought of as a metal because of the forms it is seen in as supplements, it is indeed one. A common calcium chelate that is marketed as organic calcium is calcium citrate.
Calcium citrate's benefits are that it is highly soluble and it is absorbed better by the human body than mineral forms of calcium, such as calcium carbonate. The chemical bond in calcium citrate is one of calcium bound to citric acid, another compound considered beneficial to human health. Approximately 21% of the compound is actual calcium.
Other forms of calcium supplements are also marketed, including calcium ascorbate and calcium orotate. These compounds are recommended for people with osteoporosis, a deteriorating bone disorder, or low levels of stomach acid, as a supplement that will build up bone strength quickly. Calcium carbonate must be ionized by the body before it can be absorbed, and this can limit its absorption rate to only about 4% of the total supplement taken for people with low stomach acid levels. If acid levels in the stomach are normal, 22% of calcium carbonate will be absorbed. In contrast to this, people with low stomach acid levels taking organic calcium supplements like calcium ascorbate can absorb 45% of the compound, so it is much more effective.
After the human body absorbs a calcium compound into the bloodstream, it must be used to build up bone structure. With calcium carbonate once again, much of this is instead excreted in urine. More beneficial formulations such as calcium ascorbate also contain vitamin C, which helps increase collagen levels that are required to form bone structure, and it is not as highly excreted in the urine. Many of the organic calcium products on the market are also labeled as pesticide-free calcium sources, which is another important factor to consider when purchasing supplements.
Aside from obtaining calcium in pill form to help build up bones, many organic calcium sources exist in the food supply. Calcium-rich foods at the top of the list include dairy products, such as skim milk, low-fat yogurt, and cottage cheese. Vegetables that are rich in calcium include white and black beans, soy products, and vegetables in the cabbage and broccoli family. Sardines and salmon are also a very high source of calcium.