While there are several types of calcium, the most frequently used and effective calcium supplements are calcium carbonate and calcium citrate.
Calcium carbonate is a mineral or salt used to help prevent the bone loss that occurs in osteoporosis. Calcium carbonate is the active ingredient in most OTC antacids. Calcium carbonate is inexpensive and comes in tablets (including chewable tablets), capsules, and liquid. This type of calcium supplement is taken three to four times daily. Breakfast is the best time to take calcium carbonate because the body absorbs it best when taken with a low iron meal. Calcium citrate absorbs about as well as calcium carbonate; however, it may be a better calcium supplement choice for people with reduced levels of stomach acids. Fortified fruit juices often contain calcium citrate malate. While calcium carbonate absorbs best when taken with food, calcium citrate works equally as well when taken with or without food.
Other types of calcium include calcium gluceptate, oral calcium gluconate, calcium lactate, and calcium phosphate.
Calcium salt, in conjunction with some other substance (carbonate or gluconate, for example), is what provides the calcium. Not all calcium salts contain the same amount of elemental calcium. Elemental calcium is the amount of calcium actually absorbed by the body, for example there is more elemental calcium in calcium carbonate than in calcium gluconate. Make sure the label of the calcium product you choose lists the amount of elemental calcium, as well as the total calcium. If the phrase "elemental calcium" is not listed, find another calcium supplement.
When using calcium supplements, it's important to remember that magnesium and vitamin D are essential in assisting with the absorption of calcium so that you will achieve the maximum benefit of your supplementation. Vitamin D is so important, actually, that milk is fortified with it for this reason. Many calcium supplements also include the vitamin.
Taking more than 500 mg of calcium at one time is not recommended. This is because your body cannot absorb more than 500 mg of calcium at one time. If you take more than 500 mg of calcium per day, make sure you spread your doses out over the course of the day.
Talk with your doctor if you have questions regarding the daily amount of calcium that you should be taking.
CDC. Nutrition For Everyone. Basics. http://www.cdc.gov/nutrition/everyone/basics/vitamins/calcium.html. Accessed 07/19/09.
Calcium and Vitamin D For Bone Health. UpToDate. http://www.uptodate.com/patients/content/topic.do?topicKey=~mDwe_OQdHhEOKm&selectedTitle=12~19&source=search_result. Accessed 08/24/09.
Dietary Supplement Fact Sheet. Office of Dietary Supplements - NIH. http://dietary-supplements.info.nih.gov/factsheets/calcium.asp. Accessed 08/24/09.