Calcium Supplementation in Postmenopausal Women to Reduce the Risk of Osteoporotic Fractures

Benefits of Calcium and Vitamin D

Calcium is essential for various body functions, such as nerve impulse transmission, muscle contraction, and blood clotting. About 99% of calcium is found in the skeletal system but is leeched from the bones when the plasma calcium concentration is low. With low blood levels of calcium, parathyroid hormone is secreted, leading to the synthesis of calcitriol, which results in bone resorption and the release of calcium; if abundant calcium is present in the serum, this cycle will not occur and bone turnover will return to normal levels.^[23] Due to a decrease in estrogen production after menopause, women's bodies are less able to retain calcium from dietary sources.^[24] Calcium supplementation has been used for decades to prevent this calcium depletion, maintain bone mass, and prevent and treat osteoporosis. Because peak bone mass is achieved between the ages of 25 and 35 and slowly declines thereafter, calcium supplementation is recommended for women of all ages who are unable to meet dietary calcium recommendations.^[1] Because calcium intake tends to decrease with age, calcium supplementation is especially important in postmenopausal women. Vitamin D is also fundamental to bone health, because it is essential for optimal calcium absorption. Vitamin D production by the skin also declines with age, so older individuals require more vitamin D through dietary means or supplementation. Both calcium and vitamin D are important in regulating age-related increases in parathyroid hormone and bone resorption.^[25]

Calcium is best absorbed from food sources, but most postmenopausal women do not consume enough calcium and must use supplements to achieve the recommended amount. On average, U.S. adults consume 600 mg of elemental calcium per day, far below the recommended intake.^[26] There are a number of general guidelines on how much calcium postmenopausal women should consume. A consensus statement issued in 1994 by the National Institutes of Health (NIH) recommends 1500 mg of elemental calcium per day, obtained from dietary sources or supplements, for postmenopausal women; for those under age 65 years who are taking hormone replacement therapy, the recommended daily calcium intake is 1000 mg.^[27] These guidelines also recommend 600–800 IU of vitamin D per day. NIH has also stated that without sufficient calcium and vitamin D, other treatments for osteoporosis cannot improve bone architecture. Another guideline comes from the Institute of Medicine (IOM) Food and Nutrition Board, which recommends 1200 mg of elemental calcium per day.^[28] That panel also recommends 400 IU of vitamin D per day for patients 51–70 years of age and 600 IU daily after age 71. The National Osteoporosis Foundation^[29] (NOF) and AACE^[1] support the IOM recommendation on postmenopausal calcium intake. NOF recommends 800–1000 IU of vitamin D after age 50; AACE recommends 800 IU for the elderly.

Am J Health Syst Pharm. 2011;68(4):309-318. © 2011 American Society of Health-System Pharmacists, Inc.

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