When calcium is not absorbed, it may lead to deposits in the arteries and joints, high blood pressure, kidney stones and fractures. Absorption is one of the most important considerations when choosing a bone building supplement.
The effectiveness of a supplement depends on the elemental calcium in the tablet; solubility; and on our body's ability to absorb the mineral into our bones rather than our soft tissue. It is important to understand the basics of vitamin supplements before choosing the best calcium for osteoporosis treatment and prevention.
Calcium Magnesium
ELEMENTAL CALCIUM
Elemental calcium is the amount of the mineral that is available to our body for absorption. Normally, this is the total amount of calcium listed on the label under the "Nutrition Facts" panel...which is quite different than the weight of each tablet. The weight of a tablet is affected by whatever it is bound to- such as carbonate, citrate, lactate or gluconate. A greater percentage of elemental calcium means that fewer tablets are needed to achieve the desired intake. For example, elemental calcium accounts for 40% of a calcium carbonate compound but only 24% of a calcium citrate tablet.
SOLUBILITY
Solubility refers to the amount of the mineral that can be dissolved in water at a neutral ph. In other words, if stomach acid levels are high, most forms of calcium are soluble-depending on the source of the mineral. Unfortunately, low stomach acid may be a concern for many people who are taking a bone building supplement. According to Dr. Michael Murray in the book Encyclopedia of Nutritional Supplements, studies indicate that 40% of postmenopausal women are severely deficient in stomach acid. Dr. Murray argues that people with insufficient stomach acid can only absorb about 4% of calcium carbonate versus 22% in people with normal stomach acid. When calcium is not absorbed, it may lead to deposits in the arteries and joints, high blood pressure, kidney stones and fractures.
ABSORPTION
Calcium absorption varies with the source of the mineral as well as how much is consumed at one time. As the body can only absorb 500 mg of elemental calcium at one time, it is best to take supplements three times during the day with 4 to 6 hours between doses. Toxicity may only occur with doses over 2,500 milligrams of the mineral per day.
IS CALCIUM CITRATE ABSORBED MORE EASILY THAN CALCIUM CARBONATE?
Many people think that calcium citrate will provide the solution to low stomach acid. But research indicates that calcium citrate and calcium carbonate have similar absorption if calcium carbonate is taken with meals.
The following table compares the absorption rate of supplements that provide 500 mg of elemental calcium.
Calcium Citrate Malate (CCM): 40% Calcium Carbonate: 26% Calcium Citrate: 22%
Some research suggests that calcium bisglycinate and calcium formate have even higher absorption rates than CCM. These forms of the mineral are found in leafy green vegetables and some food based supplements. Absorption rates for calcium carbonate and calcium citrate are similar if taken with meals-while calcium lactate (from cow's milk) and calcium gluconate (highly promoted in liquid formulation) have solubility less than calcium citrate.