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Know Your Supplements: Calcium Supplements

Updated: Aug 19, 2021

Calcium is the most abundant mineral in the body, and plays as vital role in the functioning of our body. It is common knowledge that calcium contributes to the structure and function of our bones and teeth, but do you also know that it is also needed for the contraction and relaxation of muscles and blood vessels, hormonal secretion, nerve and cell signalling, etc...?

The body uses the bones as a store for and source of calcium. As a consequence, our bones are constantly in a state of remodelling through bone resorption (dissolution of bone, releasing calcium into the blood stream) and deposition (formation of new bone material).

Pregnancy and Breastfeeding

During pregnancy and breastfeeding, the mother needs sufficient calcium to support the nutritional needs of the developing fetus and growing infant respectively. Calcium is also needed to prevent excessive maternal bone loss through the resorption process. Research suggests that during breastfeeding, women may lose about 3-5 percent of their bone mass.

There are good news though, as it appears that such bone loss is generally recovered a few months after the end of pregnancy or after weaning.

Age-Related Bone Loss

With age (particularly when one reaches age 40), the rate of bone resorption exceeds the rate of bone deposition. This is particularly evident in postmenopausal women due to decreased estrogen levels. The net result? Bone loss and increased risks of osteoporosis.

Ensuring sufficient calcium intake can help to reduce the extent of bone loss and is part of maintaining good nutritional status.

You may obtain dietary calcium from dairy products, fortified soymilk, tofu, sardines with bones and some vegetables such as kale and broccoli. For individuals who are unable to consume enough of these foods to meet their calcium requirements, supplementation becomes beneficial.

Calcium supplements are formulated with different calcium salts, the most common being calcium carbonate and calcium citrate.

Calcium carbonate has the highest amount of elemental calcium by weight (40%) and is inexpensive. However, this form of calcium appears to be more constipating, causes more gastric bloat and abdominal discomfort than other calcium salts. In addition, it is recommended to be taken after meals to 1.) reduce gastric side effects, and 2.) to improve absorption as calcium carbonate is better absorbed in the presence of gastric acid.

Calcium citrate has less elemental calcium by weight, about 21%. However, it causes fewer gastric side effects than calcium carbonate and can be taken without regards to food as its absorption is not affected by gastric acid. That said, individuals suffering from achlorhydria or taking gastric acid suppressants (eg. omeprazole, esomeprazole) might benefit from taking calcium citrate instead of calcium carbonate.

Calcium gluconate and calcium lactate contain much less elemental calcium by weight and are thus not commonly used as supplements.

Generally, calcium phosphate, calcium gluconate and calcium lactate are also limited in terms of studies on their use as calcium supplements.

What about Vitamin D?

Many calcium supplements are formulated with ergocalciferol or cholecalciferol - a.k.a Vitamin D2 and Vitamin D3 respectively. Vitamin D aids in the absorption of calcium. It is generally recommended to take 600 - 800iu of vitamin D a day. You may also be instructed by your doctor to take a higher dose of vitamin D, especially if you have been diagnosed to be in deficiency.

Trivia: Commercially, ergocalciferol is derived from yeast while Cholecalciferol is derived commonly from animals (in particular, lambs' wool) and more recently, lichen.

The more, the better?

Not true in the case of calcium supplementation - excessive calcium intake leads to hypercalcemia, which in turn causes nausea, muscle weakness, brain disturbances etc. Vascular and soft tissue calcification, and kidney stones may also occur in addition to other health issues.

Similarly, excessive vitamin D intake risks toxicity and can lead to hypercalcemia.

It is therefore important to stick to the recommended dietary allowances (RDAs) as mentioned earlier.

More about the products:


  1. Calcium: Fact Sheet for Health Professionals

  2. Vitamin D: Fact Sheet for Health Professionals

  3. Demontiero O, et al. Aging and bone loss: new insights for the clinician. Ther Adv Musculoskelet Dis. 2012;4(2):61-76. doi:10.1177/1759720X11430858

  4. Trailokya A, et al. Calcium and Calcium Salts. JAPI. 2016.

  5. Pregnancy, Breastfeeding and Bone Health

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