What is Calcium and Why is it Important?

Calcium is the fifth most abundant mineral by mass in the human body. Calcium primarily makes up the teeth and bones but is also important in cellular processes such as neurotransmitter release, muscular contraction, and the electrical conduction systems in the heart.

Food Sources

Dairy products, like milk and cheeses, are the most recognized sources for calcium. It can be found in a variety of different foods such as, seaweed, kelp, almonds, hazelnuts, sesame seeds, soy beans, figs, quinoa, and broccoli.

calcium mineral foods sources

calcium mineral foods sources

Also, there are several drinks that are fortified with calcium like orange juices and soy or almond milks. In addition to dairy products, calcium is also available in mineral and vitamin supplements. Also see vitamin b12 information.

Recommended Dosage

The recommended daily dose of calcium is between 1000mg and 1500mg over the entire day. Most calcium supplements are 600mg per dose because most experts report that the percentage of absorption decreases as the amount of calcium in the supplement increases.


Different Forms of Calcium

There are two main forms of calcium in supplements, they are calcium carbonate and calcium citrate.

Calcium carbonate is the most common and the least expensive and should be taken with food. Calcium carbonate absorption depends on an acidic pH in the intestine.The average absorption percentage for calcium carbonate is about 40% which is about 400mg per 1000mg ingested and is similar to the absorption percentage for most dairy products.

Most people can tolerate calcium carbonate well, there are some reports of gastrointestinal discomfort and gas. It has also been reported that adding magnesium to a supplement of calcium carbonate can increase absorption.


Calcium citrate is more expensive than calcium carbonate but can be taken without food. Calcium citrate can be taken by patients that take proton-pump inhibitors (such as Prilosec) and H2 antagonist (such as Zantac) because it does not need as acidic an environment in order to be absorbed.

Calcium citrate has an average absorption percentage of about 21%, which is about 210mg absorbed per 1000mg ingested.


Calcium Side Effects

Most forms of calcium have a very low toxicity and has very few side effects. The most commonly reported side effect from calcium ingestion is kidney stones. However, excessive consumption of calcium carbonate supplements or antacids can cause milk-alkali syndrome. Milk-alkali syndrome can result in hypercalcemia (high levels of calcium in the blood) or potentially kidney failure.

The symptoms for high blood calcium include; kidney stones, bone pain, abdominal pains, nausea, vomiting, and at extreme levels can cause heart attack. Another possible side effect of calcium supplements is the diminished effectiveness of thyroid medications when taken within four to six hours of each other.

If a person has low calcium intake or absorption, they could develop osteoporosis. Osteoporosis is a condition in which the bones loose their density and can become fragile and tend to fracture more easily. When a person in young, the body can more efficiently absorb and store calcium in order to build strong bones.

As a person ages, their body does not store calcium as effectively, which can lead to bone loss. After menopause, women can loose bone mass at a rate of 2%-4% per year. Men tend to loose bone mass after age 50 but at a lower rate than women.

After age 65, both men and women tend to loose bone mass at the same rate. Therefore, increasing their calcium intake can help slow down bone loss that can occur naturally.

This article is for information purposes. Consult your physician before adding calcium to your current medications.


More Resources and Information about Calcium

Calcium – Wikipedia, the free encyclopedia

Osteoporosis – Nutrition Australia

Ministry of Health: Nutrient Reference Values for Australia and New Zealand: Calcium



The information written here is not meant as medical advice. Please talk to your doctor or other qualified health professional prior to following what is written on the article or taking herbal supplements of any kind.