Calcium Facts

Calcium, an element in the periodic table with the chemical symbol Ca. Calcium is one of the mineral salts found in the earth’s crust and throughout many food sources. Calcium is the most abundant mineral in the human body and is vital to healthy body functioning, including bone growth, heart, muscle and nerve function.

Calcium in its natural state is difficult to digest because it is relatively insoluble. But combined with other Vitamin D, calcium becomes more easily absorbed. A person can only absorb 500-600 mg of calcium at a time. Therefore, proper timing and dosage is important.  Calcium constitutes between 1.5 and 2.0% of a person’s body weight and is needed first and foremost, for proper bone and tooth enamel development. Approximately 98% of the calcium absorbed by the body is used for bones and 1% is found in teeth. The remaining calcium intake is used to facilitate blood clotting, muscle contraction, and nerve conduction. Calcium not only provides structure to bones and teeth but also aids in weight loss by binding to fatty acids that get eliminated through the feces.

The normal level of calcium in the blood is approximately 10 mg. per 100 ml. of blood. When the amount of calcium drops below this level, the parathyroid glands secrete more parathyroid hormone (PTH), which in turn increases intestinal absorption of ingested calcium and extracts more calcium from the bones. The result is that calcium blood level returns to normal, but the bones become weaker due to loss of calcium. If the loss of calcium is not replaced, further progression of bone density loss can lead to osteoporosis. Women over the age of 51 are at risk for osteoporosis and need additional calcium (1200 mg/day) to prevent bone loss.

Doctors often prescribe or recommend daily calcium drug or supplements, especially for post-menopausal women who have either been diagnosed with or at risk for significant bone loss. These supplements come in different varieties, forms, and dosages.  Calcium from foods is the preferred source, however if supplements are required, selecting the best source that is right for you is crucial.  Taking calcium supplements at the right time and dose is just as important as what type of calcium source is best for your age and health condition

Supplement Types:

Calcium Citrate:  (Acidic form) As the body ages, stomach acid is decreased. Older individuals will benefit most from calcium citrate, as the calcium is already in the acidic form.

Calcium Carbonate:  (Alkaline form) less expensive form of calcium and is used in most calcium supplements. Best when taken with an acidic food such as orange juice.

Calcium is best absorbed when taken in doses ≤ 500 mg and ingested with food, preferably an acidic food such as orange juice and Vitamin D.

Even though spinach is a good source of calcium, the oxalates found in spinach hinder the absorption of calcium.

Nutrients That Enhance Calcium Absorption

Nutrients and compounds that inhibit absorption

Vitamin D

Oxalic Acid: *


Phytic Acid:**




Excessive mg and in

Xylitol: sugar alcohol







Compounds enhancing Calcium loss

Excessive Calcium intake inhibits absorption of:

Increased Sodium intake


Increased Protein Intake

Fatty Acid




* Foods containing high amounts of oxalic acid are poor food choices for calcium, as oxalic acid binds calcium and prevents calcium absorption. Food sources that contain oxalic acid are spinach, rhubarb, eggplant, strawberries, beets, blueberries, pecans, swiss chard, and celery.

** Foods containing high amounts of phytic acid can bind calcium and prevent absorption if consumed in large amounts. Foods containing phytic acids are wheat bran, seeds, and legumes. However, these foods in moderation are healthy and advised.