Self-Care Counseling for Calcium and Vitamin D Supplementation
© 2013 American Pharmacists Association. All Rights Reserved.
Considerations With Calcium And Vitamin D Supplementation
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Calcium is an electrolyte involved in many systems in the body including bone health, nerve signaling pathways, muscle contractions, and other intracellular processes.
Approximately 99% of the body’s calcium is stored and regulated via the skeletal system.
During the early years of life, calcium is predominantly stored through increased bone formation. Optimization of bone health early in life is important because bone
hemostasis is shifted toward bone breakdown (resorption) during the later years of life.
A combination of older age and decreased calcium intake can lead to an increased risk of bone fractures. Calcium supplementation is recommended in specific patient
populations to reduce the risk of fractures and subsequent complications. Although the role of vitamin D in fractures is not as well defined as calcium, appropriate vitamin D intake is involved in the absorption and hemostasis of calcium. The National Health and Nutrition Examination Survey (NHANES) found that more than 43% of the U.S.
population older than 1 year of age use supplemental calcium and more than 37% use a supplement containing vitamin D.
1,2Appropriate calcium and vitamin D intake through dietary sources—along with supplementation in specific patients—are required to reduce long-term complications associated with bone health.
Calcium is found in a variety of dietary sources including dairy products, certain vegetables, fortified grains, and other foods. Although a variety of foods contain calcium, the amount of calcium absorbed from the diet averages approximately 30%
and may not be sufficient to achieve the recommended daily intake. Calcium
supplements may be appropriate in patients unable to achieve the recommended daily intake through their diet. The NHANES study observed inadequate intake of calcium in all females greater than 4 years of age, specifically adolescents and women greater than 70 years of age. In addition, insufficient calcium intake was observed in males 9 to 18 years of age and men greater than 51 years of age.
1,2The recommended daily intake of calcium depends on the age of the patient as calcium
hemostasis changes during the lifetime (Table 1).
1-3Bone regulation is shifted toward
Self-Care Counseling for Calcium and Vitamin D Supplementation
© 2013 American Pharmacists Association. All Rights Reserved.
bone formation in children and adolescents leading to peak bone mass at approximately 30 years of age followed by breakdown in the later adult years. Calcium deficiency manifests over an extended period of time as the skeletal system is utilized to maintain blood calcium homeostasis. The long-term consequences of calcium deficiency manifest as osteopenia, which can lead to osteoporosis and increased risk of bone fractures.
2Table 1. Recommended Daily Allowance of Calcium
3Age Male Female
a0–6 months — —
6–12 months — —
1–3 years 700 mg 700 mg
4–8 years 1,000 mg 1,000 mg
9–13 years 1,300 mg 1,300 mg
14–18 years 1,300 mg 1,300 mg 19–30 years 1,000 mg 1,000 mg 31–50 years 1,000 mg 1,000 mg 51–70 years 1,000 mg 1,200 mg
>70 years 1,200 mg 1,200 mg
a
Includes pregnant and lactating women 14–50 years old.
Although appropriate calcium intake is necessary in all patients to avoid long-term consequences, specific patient populations have been identified to be at a greater risk.
Decrease in estrogen production in postmenopausal women increases bone breakdown and decreases absorption of calcium. Vegetarians and patients with lactose intolerance also are at risk for calcium deficiency owing to limited intake of calcium-rich foods. In addition, intake of vegetables rich in oxalic and phytic acids can decrease calcium absorption through binding in the gastrointestinal tract. Other risk factors for
osteoporosis include being female, white, having a thin build, inactivity, advanced age, smoking, excessive alcohol intake, and a family history of osteoporosis.
2,3Patients at increased risk for the consequences of calcium deficiency should be encouraged to supplement calcium intake and participate in regular weight-bearing or resistance exercise to maintain a healthy skeletal system.
Calcium supplementation is an important component for bone health and body signaling, but excessive calcium intake may be detrimental. Hypercalcemia is rarely caused by overuse of supplements and is usually associated with renal insufficiency, hyperparathyroidism, and malignancy. However, excessive calcium supplementation has been associated with an increased risk of nephrolithiasis due to formation of calcium oxalate crystals. Interestingly, increased dietary intake of calcium was not associated with the increased risk of kidney stones.
2Increased risk of cardiovascular disease and stroke has been observed with calcium
supplementation. A recently published study analyzed cardiovascular death utilizing
Self-Care Counseling for Calcium and Vitamin D Supplementation
© 2013 American Pharmacists Association. All Rights Reserved.
information from the NHANES III database. The authors found no clear association between dietary or supplemental calcium and cardiovascular death. There was increased mortality associated with cardiovascular disease with serum calcium levels
<1.16 mmol/L and with ischemic heart disease in women with serum calcium levels
>1.31 mmol/L.
4A majority of the other studies that show a positive correlation are observational and robust prospective studies have yet to be conducted to elucidate this association. Overall, the data raise questions regarding appropriate supplementation of calcium and association with cardiovascular disease. Patients should be thoroughly evaluated to determine the risk-to-benefit ratio of adding calcium supplementation.
A variety of oral calcium supplements are currently available over the counter (OTC).
The calcium salt in the product determines the amount of elemental calcium and adverse effect profile. Calcium carbonate products are available as capsules, tablets, suspensions, and most notably as a chewable tablet for acid suppression. It contains 40% elemental calcium and must be taken with meals because it requires an acidic environment for optimal absorption.
5Calcium citrate is another common OTC calcium supplement that contains 21% elemental calcium and may be taken with or without a meal.
6Other calcium salts are available, such as calcium acetate. Although ingestion of calcium acetate will have inherent absorption of calcium, these products are utilized as a binding agent to treat patients with hyperphosphatemia. Following ingestion with a meal, these phosphate binders will preferentially bind to phosphorus in food thereby preventing absorption. These products are useful for patients with chronic kidney disease unable to properly eliminate phosphorus. It is important for health care providers to evaluate the calcium salt to ensure the patient is taking the supplement appropriately and in sufficient quantity.
Common adverse effects associated with calcium supplementation include the abdominal discomforts of gas and constipation. Gastrointestinal adverse effects are more commonly seen with use of calcium carbonate salts compared with calcium citrate.
Decreasing the dose and increasing the frequency of supplementation may help reduce these symptoms. Changing to a different calcium salt should be considered in patients who are unable to tolerate the abdominal adverse effects.
Absorption of calcium supplements depends on a variety of factors. In general, with an increased dose of calcium, the percent absorbed conversely decreases. Patient
counseling should include instructions to take no more than 500 mg of calcium at a time
and separate calcium supplements throughout the day to achieve the appropriate daily
intake. Calcium will bind with specific medications if taken concomitantly, thereby
decreasing absorption and efficacy of the medication. Quinolones, tetracyclines, and
levothyroxine will bind to calcium salts in the gastrointestinal tract. Although thiazide
diuretics do not have a direct interaction with calcium absorption, these diuretics are
calcium sparing and concomitant use may increase the risk of hypercalcemia. An overall
review of the patient’s medication list should include assessment of supplements to
avoid interactions.
Self-Care Counseling for Calcium and Vitamin D Supplementation
© 2013 American Pharmacists Association. All Rights Reserved.
Vitamin D (calciferol) is a prohormone essential for absorption of calcium and regulation of calcium hemostasis. It is a lipophilic vitamin that has two major forms in the body:
ergocalciferol (vitamin D
2) and cholecalciferol (vitamin D
3). Ergocalciferol is found in fortified foods and OTC supplements. Cholecalciferol is unique in that it can be
synthesized in human skin through exposure to sunlight and it is also found in food from animal sources.
2These forms of vitamin D act similarly in the body and require
activation by enzymes. The first step of metabolism occurs in the liver, converting the inactive forms to 25-hydroxyvitamin D (25OHD or calcidiol). 25OHD is the predominant form of vitamin D found circulating in the body bound to vitamin D proteins. The final step of metabolism converts 25OHD to 1,25-dihydroxyvitamin D (calcitriol) in the kidney.
Calcitriol is the active form of vitamin D that regulates calcium and phosphorus in the body. Unfortunately, this form of vitamin D is generally poor for evaluating vitamin D status because of its very short half-life and its production is not directly related to the amount of vitamin D intake. Since vitamin D cannot be directly measured due to sequestration in fatty tissues, 25OHD is utilized as a surrogate biomarker for supply of vitamin D to the body. Measurement of this precursor takes into account both forms of vitamin D from oral intake and skin biosynthesis. The target goal of vitamin D that correlates with optimal bone health has not been established. The Institute of Medicine has suggested that 25OHD levels should be >20 ng/mL.
3Although the therapeutic range remains undefined, higher levels may be associated with increased risk of cancer and bone fractures.
2,3The benefit of vitamin D intake for decreasing the risk of bone fractures is unclear. The available data are confounded by the utilization of calcium supplementation with vitamin D. Although there is currently not a measurable benefit to the addition of vitamin D supplementation, appropriate intake may improve calcium absorption and reduce the risk of hip fractures when used in combination with calcium
supplementation. According to the NHANES report, 41.6% of adults had 25OHD levels below the recommend goal.
1,2Vitamin D supplementation should be provided daily; it is absorbed readily regardless of food. Recommendations for intake depend on age and whether the patient is
considered deficient based on measured 25OHD levels (Table 2).
3Other supplemental
sources of vitamin D including multivitamins or combination calcium and vitamin D
products should be noted to ensure the patient is receiving the appropriate amount of
vitamin D. Vitamin D supplementation is well tolerated with minimal adverse effects,
although excessive vitamin D intake may precipitate hypercalcemia.
Self-Care Counseling for Calcium and Vitamin D Supplementation
© 2013 American Pharmacists Association. All Rights Reserved.
Table 2. Recommended Daily Allowance of Vitamin D
3Age Male Female
a0–6 months — —
6–12 months — —
1–3 years 600 IU 600 IU
4–8 years 600 IU 600 IU
9–13 years 600 IU 600 IU
14–18 years 600 IU 600 IU
19–30 years 600 IU 600 IU
31–50 years 600 IU 600 IU
51–70 years 600 IU 600 IU
>70 years 800 IU 800 IU
a
