Patient information: Calcium and vitamin D for bone health

CALCIUM AND VITAMIN D OVERVIEW

Osteoporosis is a common bone disorder that causes a progressive loss in bone density and mass. As a result, bones become thin, weakened, and easily fractured. It is estimated that more than 1.3 million osteoporosis-associated (or "osteoporotic") fractures occur every year in the United States, primarily of bone within the spine (the vertebrae), the hip, and the forearm near the wrist. (See "Patient information: Bone density testing".)

A number of treatments can help to prevent loss of bone and treat low bone mass. However, the first step in preventing or treating osteoporosis is to consume foods and drinks that provide calcium, a mineral essential for bone strength, and vitamin D, which aids in calcium break down and absorption. (See "Patient information: Osteoporosis prevention and treatment".)

CALCIUM AND VITAMIN D BENEFITS

Good nutrition is important at all ages to keep the bones healthy.

• Taking calcium reduces bone loss and decreased the risk of fracturing the vertebrae (the bones that surround the spinal cord).
• Consuming calcium during childhood (eg, in milk) can lead to higher bone mass in adulthood. This increase in bone density can reduce the risk of fractures later in life.
• Calcium also has benefits in other body systems by reducing blood pressure and cholesterol levels.
• Calcium and vitamin D supplements have been shown to help prevent tooth loss in older adults.

RECOMMENDATIONS FOR CALCIUM

General recommendations — Premenopausal women and men should consume at least 1000 mg while postmenopausal women who do not take estrogen should consume 1500 mg. You should not consume more than 2000 mg of calcium per day due to the risk of side effects.

Calcium in the diet — The primary sources of calcium in the diet include milk and other dairy products, such as hard cheese, cottage cheese, or yogurt, as well as green vegetables, such as spinach (table 1). Cottage cheese and ice cream contain approximately 150 mg of calcium per 4 oz (120 mL). Other foods, such as dark green vegetables, some nuts, breads, and cereals, supply an average of 200 mg of calcium daily. Some cereals, soy products, and fruit juices are fortified with up to 1000 mg of calcium per serving.

Calcium supplements — The body is able to absorb calcium contained in supplements as well as from dietary sources. If it is not possible to get enough calcium from dietary sources, consult a healthcare provider to determine the best type, dose, and timing of calcium supplements. Figure 1 shows the calcium and vitamin D content in commonly available supplements (table 2).

• Calcium carbonate is effective and is the least expensive form of calcium. It is best absorbed with a low-iron meal (such as breakfast). Calcium carbonate is not absorbed well in people who also take a specific medication for gastroesophageal reflux (called a proton pump inhibitor or H2 blocker). (See "Patient information: Gastroesophageal reflux disease in adults".) for a list of H2 blockers and proton pump inhibitors.
• Calcium citrate is absorbed best when it is taken on an empty stomach.
• Many natural calcium carbonate preparations such as oyster shells or bone meal contain some lead. The low lead levels in calcium supplements are unlikely to be a health risk because calcium blocks lead absorption.
• Calcium supplements should be taken in divided doses (eg, in the morning and evening). Doses above 500 mg are not absorbed as well as smaller doses.
• Calcium supplements do not replace other osteoporosis treatments. Calcium is less effective than other treatments, including hormone replacement, bisphosphonates (eg, risedronate [Actonel®] and alendronate [Fosamax®]), and raloxifene (Evista®). Calcium has additive benefits when used along with other treatments. (See "Patient information: Osteoporosis prevention and treatment".)

Underlying gastrointestinal diseases — Patients who do not adequately absorb nutrients from the gastrointestinal tract (due to malabsorption) may require more than 1000 mg of calcium per day. In such cases, a healthcare provider can help to determine the optimal dose of calcium.

Medications — All medications should be discussed with a healthcare provider to ensure that possible interactions with calcium are identified. Certain medications change the amount of calcium that is absorbed and/or excreted. As an example, loop diuretics (eg, furosemide, Lasix®) increase the amount of calcium excreted in the urine.

On the other hand, thiazide diuretics (eg, hydrochlorothiazide, HCTZ) can reduce levels of calcium in the urine, potentially reducing the risk of bone loss and kidney stones (see 'Kidney stones' below.

Side effects of calcium — Calcium is usually easily tolerated when it is taken in divided doses several times per day. Some people experience side effects related to calcium, including constipation and indigestion. Calcium supplements interfere with the absorption of iron and thyroid hormone, and therefore these medications should be taken at different times.

Kidney stones — There is little evidence that consuming large amounts of calcium (from foods and drinks) increases the risk of kidney stones, or that consuming small amounts of calcium decreases the risk. In fact, avoiding dairy products is likely to increase the risk of kidney stones.

However, use of calcium supplements may increase the risk of kidney stones in susceptible individuals by raising the level of calcium in the urine. This is particularly true if the supplement is taken between meals or at bedtime. (See "Patient information: Kidney stones in adults".)

IMPORTANCE OF VITAMIN D

Vitamin D decreases bone loss and lowers the risk of fracture, especially in older men and women. Along with calcium, vitamin D also helps to prevent and treat osteoporosis. To absorb calcium efficiently, an adequate amount of vitamin D must be present.

Vitamin D is normally made in the skin after exposure to sunlight. (See "Patient information: Vitamin D deficiency".)

Recommendations for vitamin D — The current recommendation is that all adults should consume at least 800 international Units of vitamin D per day. Lower levels of vitamin D are not as effective while high doses can be toxic, especially if taken for long periods of time.

Vitamin D is available as an individual supplement and is included in most multivitamins and some calcium supplements (table 2). Milk is the best dietary source of vitamin D, with approximately 100 IU per cup (table 3).

WHERE TO GET MORE INFORMATION

Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two people are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.

This discussion will be updated as needed every four months on our web site (www.uptodate.com/patients). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

Some of the most pertinent include:

Patient Level Information:
Patient information: Bone density testing
Patient information: Osteoporosis prevention and treatment
Patient information: Gastroesophageal reflux disease in adults
Patient information: Kidney stones in adults
Patient information: Vitamin D deficiency

Professional Level Information:
Calcitonin in the prevention and treatment of osteoporosis
Calcium and vitamin D supplementation in osteoporosis
Causes of vitamin D deficiency and resistance
Diet in the treatment and prevention of hypertension
Epidemiology and etiology of premenopausal osteoporosis
Evaluation and treatment of premenopausal osteoporosis
Overview of the management of osteoporosis in postmenopausal women
Treatment of vitamin D deficient states

A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable.

• National Library of Medicine

      (www.nlm.nih.gov/medlineplus/healthtopics.html)

• Osteoporosis and Related Bone Diseases National Resource Center (ORBD-NRC)

      (www.osteo.org)

• National Osteoporosis Foundation

      (www.nof.org)

• Osteoporosis Society of Canada

      (www.osteoporosis.ca/)

• The Hormone Foundation

       (www.hormone.org/public/osteoporosis.cfm, available in English and Spanish)

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