Got Calcium?

Nutrition: Exploring the latest research on calcium, vitamin D and bone health.

Conventional wisdom has long held that calcium plus vitamin D offers the best antidote for age-related bone loss. In fact, those ubiquitous “Got Milk” commercials boast of the calcium-rich beverage’s ability to strengthen bones. And some research suggests that both calcium and vitamin D play a critical role in maintaining bone health (Heaney 2007).

Since calcium is a building block of bone, and vitamin D increases calcium absorption, it makes sense that when taken together, the two nutrients may prevent osteoporosis, a weakening of bones that increases the risk of bone fractures.

But now new research says that this popular notion may be incorrect.

The Latest Research Findings

To protect against bone weakening, the Institute of Medicine (IOM) recommends that most adults consume 1,000 milligrams (mg) of calcium—the equivalent of three glasses of milk per day, which is far more than most Americans get (Ma, Johns & Stafford 2007). The IOM also recommends an adult intake of between 400 and 600 International Units (IU) of vitamin D each day (IOM 2004).

But now the widely publicized results from the Women’s Health Initiative (WHI), a long-term, large-scale study of the health of American women aged 50–79, is challenging the belief that calcium intake can actually reduce fractures. More than 36,000 healthy postmenopausal women—individuals at the highest risk for osteoporosis—participated in the WHI’s calcium plus vitamin D trial (Jackson et al. 2006). Half of the women were randomly assigned to receive 1,000 mg of elemental calcium and 400 IU of vitamin D in supplement form, while the other half received a placebo over the 7-year study period. Surprisingly, the women who received the calcium and vitamin D supplements experienced only a small increase in hip bone density, no reduction at all in hip fractures and—of most concern—an increased risk of kidney stones (Jackson et al. 2006).

Additionally, a research review that analyzed the results from 15 other high-quality trials (not including the WHI study), representing a total of 1,806 postmenopausal participants, reached a similar conclusion: calcium supplementation has a slight effect on bone density and shows a trend toward reduction in vertebral fractures, but it is uncertain if calcium decreases the incidence of nonvertebral fractures (Shea et al. 2004).

These findings suggest that calcium and vitamin D supplementation may not prevent osteoporosis, and what’s more, may do little to prevent the most dreaded consequence of the bone disease—hip fracture. Yet even in light of these findings, few experts are willing to declare calcium and vitamin D unnecessary for building bone strength and preventing osteoporosis. Here’s why.

Putting This Research Into Context

The existing body of research on calcium/vitamin D is inconclusive and imperfect. For example, the WHI study, while well-designed, had several important limitations. First, its results generally can be applied only to healthy women aged 50–79 (the age group studied). Second, both the supplement and placebo participants were allowed to take multivitamins and other supplements in addition to the study-prescribed dose of calcium and vitamin D. Therefore, it is still possible that calcium and vitamin D could protect against osteoporosis and fractures, but few differences were noted between the two groups of participants because even the control group had a high intake of these nutrients from other sources. In fact, 64% of the women in the placebo group had a daily calcium intake of at least 800 mg at baseline, and 42% had a daily vitamin D baseline intake of at least 400 IU (Jackson et al. 2006; Finkelstein 2006). Third, the WHI study included results from participants who did not adhere to the assigned therapy. When data were excluded after a participant’s adherence fell below 80% of the study’s daily prescribed supplement dose, the authors found that the risk of hip fractures was significantly reduced in the calcium/vitamin D group (Jackson et al. 2006; Finkelstein 2006). Also, the prescribed amount of 400 IU of vitamin D may not have been enough to detect a benefit to bone health, since other similar trials have demonstrated benefits when the dose was at least as high as 700 IU per day (Bischoff-Ferrari et al. 2005).

Supplementation Just May Help

The fact is that the overall body of research on the role of calcium and vitamin D in the prevention of osteoporosis is too limited in scope and quantity to draw any firm conclusions. So if calcium and vitamin D could help reduce the incidence of osteoporosis without causing harm, it is reasonable to encourage all Americans to consume the recommended amount of the nutrients. After all, osteoporosis is a serious and potentially disabling condition affecting 10 million Americans with another 34 million at high risk (National Osteoporosis Foundation 2007). Characterized by low bone density and diminished bone strength, this condition is responsible for more than 1.5 million fractures, including 300,000 broken hips each year (National Osteoporosis Foundation 2007). Hip fracture, the most serious consequence of osteoporosis, can create a cycle of hospital admission, serious disability and a 10%–20% increased mortality risk (Sambrook & Cooper 2006).

There are other factors that equally contribute to the development of osteoporosis, such as accelerated bone loss in older age and a low peak bone mass from suboptimal bone growth during childhood, adolescence and young adulthood (we stop building bone at about age 30), according to the National Institutes of Health Consensus Development Panel on Osteoporosis Prevention, Diagnosis and Therapy (NIH 2001). While some experts believe that calcium supplementation during childhood can increase bone mineral density, and thus presumably decrease the risk for fracture or osteoporosis later in life, studies suggest that calcium supplementation does not offer a significant benefit to youth (Lanou, Berkow & Barnard 2005; Winzenberg et al. 2007).

Navigating This Maze of Research

Ultimately, when trying to make sense of the role of calcium in bone health, the latest research findings should not be ignored. The bottom line is that calcium and vitamin D alone do not assure optimal bone health. Rather, the best solution is to take a multipronged approach that combines nutrition, lifestyle, exercise and fall prevention.

This is where you come in: fitness professionals can play a key role in helping their clients and participants to build and maintain strong bones and avoid osteoporosis and bone fracture by following these steps.

5 Steps to Optimal Bone Health
  1. Start With Good Nutrition. Proper nutrition involves more than simply meeting the current calcium and vitamin D recommendations. (Of course, clients should be informed that a deficiency in either nutrient can preclude optimal bone health, so encourage them to get the recommended daily amounts of calcium and vitamin D.) An overall healthy and balanced diet that provides adequate calories and appropriate nutrients will provide a solid foundation for all body tissues, including bone. Also, clients should ensure that they get enough vitamin K (found primarily in green, leafy vegetables and some vegetable oils), as this nutrient might also help decrease fracture risk (Cockayne et al. 2006).
  2. Maintain an Overall Healthy Lifestyle. Eating disorders, especially anorexia nervosa, smoking and depression all contribute to bone weakening and increase the risk of osteoporosis (NIH 2001). Although maintaining a healthy weight is important for overall health, thinner people tend to be at increased risk for osteoporosis (NIH 2001). Research suggests, however, that individuals who lose weight primarily through exercise (as opposed to calorie restriction) do not have reduction in bone mineral density at clinically important fracture sites, such as the hip (Villareal et al. 2006).
  3. Engage in Weight-Bearing Physical Activity. Exercise early in life leads to a higher peak bone mass. Exercise late in life likely slows the decline in bone mineral density and increases muscle mass and strength more than twofold in frail persons (NIH 2001). Additional benefits of regular physical activity include improved function, delayed loss of independence and improved quality of life. Most important, elderly individuals who engage in regular physical activity are less likely to fall (NIH 2001).
  4. Aim to Prevent Falls. Muscle strengthening, balance training or a regular body-mind program can help prevent falls (Gillespie et al. 2003). Other simple remedies such as removing rugs and clutter and other home hazards, eliminating psychiatric medications when possible and adhering to a multidisciplinary program to assess risk factors have all been found to substantially reduce the incidence of falls (Gillespie et al. 2003). And that, in turn, means a reduction in debilitating fractures.
  5. Visit a Doctor Regularly. This advice is especially true for clients with known risk factors for osteoporosis, which include:
  • female gender
  • increased age
  • estrogen deficiency (postmenopausal)
  • Caucasian race
  • low weight and body mass index
  • family history of osteoporosis
  • smoking
  • history of prior fracture (NIH 2001)

A physician can order a dual-energy X-ray absorptiometry (DXA) bone scan to confirm or rule out a diagnosis of osteoporosis. Also, several medications are available for the treatment and prevention of the bone disease.

Spread the Word

Calcium and vitamin D are the foundation on which to build strong bone, but alone they are not enough to prevent osteoporosis and fractures. Encourage your clients to complement their intake of these nutrients with regular weight-bearing exercise; to stop smoking; and to rid their homes of fall hazards. Only then can they avoid the devastating consequences of a brittle or broken bone.

 

SIDEBAR: Good Food Sources of Calcium

Food

Amount

Calcium (mg)

yogurt, plain, low fat

8 oz

415

collards, frozen, boiled

1 cup

357

skim milk

1 cup

306

spinach, frozen, boiled

1 cup

291

yogurt, plain, whole milk

8 oz

275

black-eyed peas, boiled

1 cup

211

canned salmon

3 oz

181

cheese food, pasteurized American

1 oz

162

trail mix (nuts, seeds, chocolate chips)

1 cup

159

baked beans, canned

1 cup

154

cottage cheese, 1% milk fat

1 cup

138

iceberg lettuce

1 head

97

green peas, boiled

1 cup

94

oranges

1 cup

72

almonds

1 oz (24 nuts)

1 oz (24 nuts)


Key: mg = milligrams.
Source: Pennington 1998.

SIDEBAR: Good Food Sources of Vitamin D

Food/Item

Amount

Vitamin D(IU)

sunlight

About 10–15 minutes without sunscreen 2–3 times per week

“more than adequate”(per NIH Office of Dietary Supplements 2005)

salmon, cooked

3.5oz

360

tuna fish, canned in oil

3oz

200

milk, nonfat, reduced fat, and whole, vitamin D-fortified

1 cup

98

egg (vitamin D is found in egg yolk)

1 whole

20


Key: IU = International Units.
Source: Pennington 1998.
SIDEBAR: Additional Resources
  • National Osteoporosis Foundation: (http://www.nof.org/) Provides an abundance of information and resources about osteoporosis including facts, support groups and advocacy information, plus a tool to locate a local doctor with expertise in osteoporosis and bone health
  • National Institutes of Health, Medline: Osteoporosis: (http://www.nlm.nih.gov/medlineplus/osteoporosis.html) Basic information about osteoporosis with links to numerous websites and web pages devoted to different issues of concern regarding osteoporosis, such as the latest news, risk factors, screening and prevention treatment
  • National Institutes of Health Office of Dietary Supplements: (Calcium Supplement Fact Sheet. http://dietary-supplements.info.nih.gov/factsheets/calcium.asp. Vitamin D Fact Sheet. http://dietary-supplements.info.nih.gov/factsheets/vitamind.asp.) These comprehensive fact sheets describe the main functions and roles of calcium and vitamin D, and teach people how to best meet their calcium and vitamin D needs.
  • Harvard School of Public Health Calcium & Milk pamphlet: (www.hsph.harvard.edu/nutritionsource/calcium.html.). An overview of osteoporosis, the role of calcium and vitamin D in its prevention, and a discussion of the best sources of these nutrients

 

Natalie Digate Muth, MPH, RD, CSCS, is a registered dietitian and medical student at the University of North Carolina at Chapel Hill. She is also an ACE master trainer.

References
Bischoff-Ferrari, H.A., et al. 2005. Fracture prevention with vitamin D supplementation: A meta-analysis of randomized controlled trials. Journal of the American Medical Association, 293 (18), 2257–64.

Cockayne, S. et al. 2006. Vitamin K and the prevention of fractures. Archives of Internal Medicine, 166, 1256–61.

Finkelstein, J.S. 2006. Calcium plus vitamin D for postmenopausal women—bone appétit? The New England Journal of Medicine, 354 (7), 750–52.

Gillespie, L.D. et al. 2003. Interventions for preventing falls in elderly people. Cochrane Database of Systematic Reviews, Issue 4. Art. No.: CD000340. DOI: 10.1002/1465
1858.CD000340.

Heaney, R.P. 2007. Bone health. American Journal of Clinical Nutrition, 85 (suppl), 300S–303S.

Institute of Medicine (IOM) Dietary Reference Intakes for Calcium, Magnesium, Phosphorus, Vitamin D, and Fluoride. Washington, DC: National Academy Press.

Jackson, R.D. et al. 2006. Calcium plus vitamin D supplementation and the risk of fractures. The New England Journal of Medicine, 354 (7), 669–83.

Lanou, A.J., Berkow, S.E. & Barnard, N.D. 2005. Calcium, dairy products, and bone health in children and young adults: A reevaluation of the evidence. Pediatrics, 115 (3), 736–43.

Ma, J., Johns, R.J. & Stafford, R.S. 2007. Americans are not meeting current calcium recommendations. American Journal of Clinical Nutrition, 85 (5), 1361–66.

National Institutes of Health (NIH) Consensus Development Panel on Osteoporosis Prevention, Diagnosis, and Therapy. 2001. Osteoporosis prevention, diagnosis, and therapy. Journal of the American Medical Association, 285 (6), 785–95.

NIH Office of Dietary Supplements. 2005. Dietary Supplement Fact Sheet: Vitamin D. (Updated 8/5/2005.) http://dietary-supplements.info.nih.gov/factsheets/vita
mind.asp; retrieved May 31, 2007.

National Osteoporosis Foundation. 2007. Fast Facts. www.nof.org/osteoporosis/dis
easefacts.htm
; retrieved May 30, 2007.

Pennington, J. 1998. Bowes and Church’s Food Values of Portions Commonly Used. (17th ed.) Philadelphia: Lippincott-Raven.

Sambrook, P. & Cooper, C. 2006. Osteoporosis. The Lancet, 367, 2010–18.

Shea, B.J. et al. 2004. Calcium supplementation on bone loss in postmenopausal women. The Cochrane Database of Systematic Reviews, Issue 1. Art. No.: CD004526. DOI: 10.1002/14651858.CD004526.pub2.

Villareal, D.T. et al. 2006. Bone mineral density response to caloric restriction—induced weight loss or exercise-induced weight loss. Archives of Internal Medicine, 166, 2502–10.

Winzenberg, T.M. et al. 2006. Calcium supplementation for improving bone mineral density in children. Cochrane Database of Systematic Reviews, Issue 2. Art. No.: CD005119. DOI: 10.1002/14651858.CD005119.pub2.

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Natalie Digate Muth, MD, MPH, RD, is a registered dietitian and a recent graduate of the UNC School ... more less
October 2007

© 2007 by IDEA Health & Fitness Inc. All rights reserved. Reproduction without permission is strictly prohibited.

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