Calcium is essential to the structure of bone and teeth and vital functions such as nerve transmission and enzyme and hormone activity. This important mineral is available from dietary sources such as dairy products and in supplement form. However, some dietary and other factors can make it difficult for the body to absorb calcium, especially calcium supplements.
Insufficient Vitamin D
The parathyroid gland monitors and regulates blood calcium levels. When these levels drop, it activates a vitamin D enzyme called 1,25-dihydroxyvitamin D, which triggers the kidneys and intestines to absorb more calcium. Thus, adequate vitamin D essential to calcium absorption. Vitamin D is available in foods such as fatty fish, fish liver oils and through exposure to sunlight. Many foods, such as eggs, bread and cereal, have been fortified with vitamin D. You can also take a vitamin D supplement with your calcium supplement. Several calcium supplements are formulated with added vitamin D. Choose one with 600 IU of vitamin D, the recommended dietary allowance for adults set by the Institute of Medicine.
Choosing Calcium Supplements
The most common types of calcium supplement are calcium citrate and calcium carbonate. Calcium citrate is more easily broken down in the stomach and digested, but it contains less elemental calcium, the type of calcium the body actually absorbs. It can also be expensive. Calcium carbonate contains more elemental calcium and is more affordable. However, the elemental calcium in calcium carbonate can be difficult for the body to absorb because it requires more stomach acid to digest. The University of Maryland Medical Center recommends drinking a glass of orange or grapefruit juice with your calcium carbonate supplements to stimulate stomach acid production.
Other Nutrients and Dosage
Magnesium is also important to calcium absorption. Magnesium can be found in foods such as tofu, nuts, whole grains and green leafy vegetables or in supplement form. The recommended dosage for magnesium for adults is between 270 and 400 mg daily for men and between 280 and 300 mg for women. High levels of sodium, protein and caffeine all cause calcium to be excreted through urine instead of absorbed. To address this, keep sodium consumption low and take your calcium supplement separately from dietary sodium, proteins or caffeine. Take your calcium supplements in two separate daily doses of 500 mg each, since that is the most your body is able to absorb at one time.
When to See a Doctor
A calcium deficiency can also be caused by more serious medical issues. Hypoparathyroidism, or underactive parathyroid glands, will keep the body from absorbing enough calcium, since the parathyroid regulates the enzymes that stimulate calcium absorption. People with intestinal problems such as Crohn's disease and celiac disease may have trouble absorbing calcium. Intestinal surgery or resection can also cause difficulties. If you suspect or know you may have one of these conditions, see your doctor for diagnosis and treatment.
References
- Linus Pauling Institute; Calcium; Jane Higdon; 2003
- National Endocrine and Metabolic Diseases Information Service; Hyperparathyroidism; 2006
- University of Maryland Medical Center; Calcium; Steven D. Ehrlich; 2009
- Linus Pauling Institute; Vitamin D; Jane Higdon; 2004
- University of Maryland Medical Center; Magnesium; Steven D. Ehrlich; 2009
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