Calcium

Figure 1. The crystal structure of Calcium.

Calcium is a chemical element with the symbol Ca and atomic number 20. Calcium is the fifth most abundant element in Earth's crust, and the third most abundant metal, after iron and aluminium. The most common calcium compound on Earth is calcium carbonate. Calcium is an alkaline Earth metal.

Calcium is the most abundant metal and the fifth-most abundant element in the human body. About 99% of the body’s Calcium is stored in bones, and the remaining 1% is found in blood, muscle, and other tissues.

As electrolytes, Calcium ions (Ca²⁺) play a vital role in the physiological and biochemical processes of organisms and cells. Calcium ions outside the cell are important for maintaining the potential difference across excitable cell membranes, protein synthesis, and bone formation.

Food Sources

Calcium is not produced in the human body. The human body gets the Calcium it needs in two ways: by eating foods or supplements that contain calcium and by drawing from existing calcium within the body. If insufficient Calcium is consumed from foods, the human body will remove Calcium from bones. Ideally, Calcium that is “borrowed” from bones will be replaced at a later point. But this doesn’t always happen and can’t always be accomplished just by eating more Calcium.

Calcium is widely available in many foods, not just milk and other dairy foods. Fruits, leafy greens, beans, nuts, and some starchy vegetables are good sources of Calcium too. Some examples of Calcium rich foods include:

• Milk
• Yogurt
• Cheese
• Sardines (with bones)
  
• Soy products, such as Soy Beans, Edamame, Tofu
• Winter Squash
• Almonds
• Leafy greens, such as Collard, Turnip, Kale, Bok Choy, Spinach
  
• Fortified flour products
• White beans

Taken as a Dietary Supplement

Calcium is an essential element needed in large quantities within the human body. The Ca²⁺ ion acts as an electrolyte and is vital to the health of the muscular, circulatory, and digestive systems, is indispensable to the building of bone, teeth, and supports synthesis and function of blood cells. Calcium regulates the contraction of muscles, nerve conduction, and the clotting of blood. The intestine absorbs about one-third of calcium eaten as the free ion.

In particular, studies have suggested positive effects of Calcium in the following health applications:

• Blood pressure
• Cardiovascular disease
• Bone health
• Colorectal cancer
• Kidney stones

For bone formation, the Parathyroid hormone and Vitamin D act as a promoter by enhancing the deposition of calcium ions, allowing rapid bone turnover without affecting bone mass or mineral content.

In humans, Calcium deficiency may lead to:

• Hypocalcemia: muscle cramps and weakness, numbness or tingling in fingers, abnormal heart rate, poor appetite.
• Loss of bone mass, i.e. ostopenia and osteoporosis.

The Recommended Dietary Allowance for calcium for women 19-50 years of age is 1000mg. For women 51+ years of age: 1200 mg. For pregnant and lactating women: 1000mg. For men 19-70 years of age: 1000 mg. For men 71+ years of age: 1200mg. The Upper Limit for calcium is 2500 mg daily from food and supplements. People over the age of 50 should not take more than 2000 mg daily.

Side Effects

• Hypercalcemia: Weakness, fatigue, nausea, vomiting, shortness of breath, chest pain, heart palpitations, irregular heartbeat.
• Excessive Calcium above 2000mg daily may increase the risk of some conditions like kidney stones, prostate cancer, and constipation.

Background

Calcium was first isolated in 1808 by Humphry Davy. Calcium is listed on the World Health Organization's List of Essential Medicines.