February 2013 Issue

Bone Health and Diet
By Sharon Palmer, RD
Today’s Dietitian
Vol. 15 No. 2 P. 44

Today’s Dietitian mines the latest science to provide strategies to help clients power up on bone-friendly foods and nutrients.

If you’ve worked in healthcare long enough, you know the importance of bone health. As people develop osteoporosis—a disease that occurs in those who lose too much bone, make too little, or both—bones become weak and can break, even with a minor fall, bump, or sneeze.

Bone disease can have a devastating impact on individuals, causing pain, deformity, and a downward spiral into physical and mental health problems, such as the inability to dress oneself or walk; poor self-esteem, body image, and mood; and a feeling of isolation and helplessness. There’s also a higher risk of pressure ulcers, pneumonia, urinary tract infections, and early death. The cost of osteoporosis runs in the billions. By 2025, experts predict osteoporosis will be responsible for 3 million fractures and cost $25.3 billion per year.1,2

Unfortunately, osteoporosis isn’t rare; about 10 million Americans have it, and another 34 million are at risk. Both women and men are at risk of developing the condition as they age, but women are particularly vulnerable, as eight in 10 sufferers are female.2 Additionally, about one-half of women and up to one-quarter of men older than 50 will break a bone because of osteoporosis. Also, it’s called a “silent” condition because many people don’t know they have bone disease until they suffer a fracture.

Nutrition’s Role in Bone Protection
A growing field of science shows that diet can be an important tool in preventing bone disease. Bone health is the result of bone mass, bone architecture, and body mechanics—all of which are supported by nutrition throughout the human life cycle.

“Ninety percent of adult bone mass is in place by the end of adolescence, and it has to last you a lifetime,” says Diane Schneider, MD, a National Bone Health Alliance Governance Committee member; cofounder of 4BoneHealth, an organization to promote bone health; and the author of The Complete Book of Bone Health. “Not getting enough nutrients to develop strong bones puts people at risk later for breaking a bone or osteoporosis. A healthful, balanced diet and a healthful weight can prevent bone disease.”

The following nutrients and the foods that contain them hold particular promise in promoting optimal bone health.

Calcium
Calcium is a mineral essential for both building bones and keeping them healthy. The body uses bone tissue as a reservoir and source of calcium to maintain constant concentrations of calcium in the blood, muscles, and intercellular fluids. Bone is in a continuous state of “remodeling” under the control of osteoblasts (cells that form bones) and osteoclasts (cells that help eat away old bone). Constant resorption (breaking down and releasing minerals) and deposition of calcium into new bone occurs, and the balance changes with age. Bone formation exceeds resorption in periods of growth, such as in childhood, but is relatively equal during early and middle adulthood and in aging adults. Breakdown exceeds formation particularly among postmenopausal women.

To replace calcium loss in bones, dietary sources of calcium must be consumed. A large number of studies have found that consuming adequate amounts of calcium throughout life may delay or minimize age-related bone loss and thereby decrease the risk of osteoporosis. The Dietary Guidelines for Americans reports that adequate calcium status is important for optimal bone health and that calcium is a nutrient of concern, since low calcium intake among children aged 9 and older, adolescent girls, adult women, and adults 50 and older is common.2-4

The Institute of Medicine updated the Dietary Reference Intake (DRI) for calcium in 2010 to 1,300 mg for kids aged 9 to 18; 1,000 mg for adults aged 19 to 50 and for men aged 51 to 70; and 1,200 mg for women aged 51 to 70 and for men and women over 70. Food sources of calcium include dairy products such as reduced-fat milk, yogurt, and cheese; green vegetables; and calcium-fortified foods such as soymilk, tofu, cereals, snacks, breads, and orange juice. MyPlate now recommends people over the age of 9 consume three servings of dairy products per day.5-7

 “We know from multiple research studies that calcium is essential for bone, but the majority of Americans aren’t getting enough. Eight-five percent of girls across the country aged 9 to 13, a time of maximal bone growth with 40% of adult bone mass made during that time period, aren’t hitting their daily calcium target,” Schneider says.

How can you help your patients meet their calcium goals? “I recommend the usual suspects: milk and enriched milk alternatives, such as soy and almond milk, cheese, and yogurt. I also recommend the lesser known calcium-rich foods, such as bok choy, kale, turnip greens, almonds, white beans, tofu, and fortified orange juice,” says Kathryn Ciamaichelo, RD, lead outpatient dietitian and wellness coordinator for Sodexo Nutrition Services at Memorial Hospital in Colorado Springs.

“First, people should know their target for daily calcium intake. And No. 2, they should try to meet their daily calcium recommendations through foods first. If they don’t reach their goal with food, then fill in the deficit amount with a calcium supplement,” Schneider says. “There are many people who don’t count the calcium in food and are just taking supplements. They may be taking 1,000 mg/day in supplements in addition to calcium in foods, fortified foods, and a multivitamin and mineral supplement.”

Vitamin D
Vitamin D also is essential to bone health, as it promotes calcium absorption in the gut, maintains adequate serum calcium and phosphate concentrations for normal mineralization of bone, and supports the process of bone remodeling by osteoblasts and osteoclasts. Vitamin D deficiency can cause rickets, a disease in children characterized by soft, deformed bones. The Dietary Guidelines lists vitamin D as a nutrient of concern, noting that most dietary intakes are below recommendations.

To support bone health, the Institute of Medicine recommends 600 IU of vitamin D every day for people aged 1 to 70; 800 IU for individuals over 70; and 400 IU for infants 0 to 12 months. The National Osteoporosis Foundation takes it a step further, recommending women aged 50 and older, including healthy women and those with low bone density or osteoporosis, get 800 to 1,000 IU of vitamin D daily.2-4,6,8

There are few sources of vitamin D in the food supply. Fatty fish such as salmon, tuna, and mackerel and fish liver oils are good sources. Small amounts are found in beef liver, cheese, and egg yolks. Some mushrooms that are exposed to ultraviolet light provide varying levels. Most of the vitamin D in American diets comes from vitamin D-fortified foods, such as milk, milk products, orange juice, and cereals. However, adequate amounts of vitamin D can be obtained through synthesis in the body following sunlight exposure. Because there are few dietary sources of vitamin D and the use of sunscreen is widespread, the National Osteoporosis Foundation recommends most people take a vitamin D supplement to achieve and maintain adequate vitamin D levels for bone health.2-4,6,8

“The advice is to try and get as much vitamin D as possible from the diet, but in many cases a supplement may be needed,” says Jeri Wanzor Nieves, PhD, an associate professor of clinical epidemiology at Columbia University and the nutrition principal investigator for the New York State Osteoporosis Prevention Education Program.

“It’s also important to point out to clients that the Percent Daily Value on nutrition facts labels is set at only 400 IU, so people may be miscalculating how much vitamin D they’re getting from foods. In addition, there may be multiple factors preventing adequate vitamin D intake through sun exposure. It depends on where you live, how much casual exposure you have to sunlight, age, time of year, and body size. For the overweight or obese, it’s going to take more vitamin D to fill up the tank, and [it depends on] whether they have darker skin, which requires more vitamin D,” Schneider says.

Calcium and Vitamin D Controversy
Recent controversy has spurred a debate over just how effective calcium and vitamin D intake is for maintaining bone health as well as the potential health consequences of consuming large amounts of these nutrients. A recent analysis of calcium intakes and bone mineral density in elderly US men and women using National Health and Nutrition Examination Survey data found that a high calcium intake, beyond the Recommended Dietary Allowance for elderly women and men, most commonly achieved by calcium supplements, didn’t provide any benefit for hip or lumbar bone mineral density. And a dietary intake of calcium approaching or meeting the current recommendations wasn’t related to higher bone mineral density of the hip or lumbar spine in late life compared with lower intakes of calcium in older adults.9 A high-calcium diet also has been linked with both cardiovascular disease risk and prostate cancer.10

The US Preventive Services Task Force released its draft recommendations regarding vitamin D and calcium supplementation to prevent cancer and osteoporotic fractures in adults in July 2012, which concluded that the current evidence is insufficient to assess the balance of the benefits and harms of combined vitamin D and calcium supplementation for the primary prevention of fractures in premenopausal women or in men.11

The Harvard School of Public Health recently issued the Healthy Eating Plate, its take on the USDA’s MyPlate. Instead of recommending three servings of dairy products, the Healthy Eating Plate recommends one to two daily servings because the school reports that it’s unclear how much calcium is needed for bone health and whether dairy products are the best source of calcium.12

However, the National Osteoporosis Foundation strongly urges all individuals to get the recommended amounts of calcium and vitamin D to protect bone health. In addition, the National Bone Health Alliance advises people to consult with their healthcare professional before discontinuing the use of supplements while continuing to meet their daily calcium and vitamin D needs from food sources first, though the alliance concurs that more research is needed to better understand the risk and benefit of calcium and vitamin D supplementation.2,4

“There has been a substantial amount of research to set the DRI values, and these values are evidence based and accurate,” Nieves says. “There have been several recent controversies; however, they don’t change the DRIs. There’s evidence that with high intakes of calcium—values that exceed the DRI—there may be an elevated risk of cardiovascular events, particularly if the calcium is from supplements. Therefore, the message should be to set your goal to meet the calcium DRI with food sources when possible and that more calcium is clearly not better.”

Other Nutrients
Other nutrients that have been linked with bone health include vitamins C and K, and magnesium. Researchers from Mount Sinai School of Medicine found that vitamin C protects against osteoporosis in animals.13 Some evidence indicates that magnesium—50% of the body’s store of which is found in the bone—may protect against osteoporosis. The National Institutes of Health reports that diets providing the recommended levels of magnesium are beneficial for bone health, but further investigation on the role of magnesium in bone metabolism and osteoporosis is needed.14

Vitamin K insufficiency is linked with low bone mineral density and increased fractures, while vitamin K supplementation has been shown to improve the bone turnover profile.15 More research is needed to understand the role of these nutrients in osteoporosis prevention.

Healthful Eating Patterns
Bone health may be more about a healthful eating pattern than a focus on individual nutrients. A recent study found that in men assigned to a Mediterranean diet enriched with olive oil, levels of markers for healthier bone formation were significantly higher at the end of the study’s two-year period than they were at the start. The Mediterranean eating pattern includes a diet rich in bone-promoting foods, including fruits, vegetables, and moderate alcohol intake.16

Eating a diet rich in fruits and vegetables may protect bones through several mechanisms, including creating an alkaline environment that reduces the acidity in the body and providing more bioactive components, such as phenols and flavonoids, that act as antioxidants. Some specific fruits and vegetables have been linked to bone health, including lycopene-rich produce such as watermelon, tomatoes, pink grapefruit, bell peppers, and guava. A 2009 study found that carotenoids, particularly lycopene, help protect older women’s lumbar spine and older men’s hips against fracture.17 And one study found that postmenopausal women who enjoyed two daily drinks—either wine or beer—had 5% to 8.3% greater hip and spine bone density than nondrinkers.18 However, heavy drinking (more than two drinks per day) appears to weaken bones and increase the risk of falls.

According to Nieves, the current body of evidence suggests that many nutrients may be beneficial for bone health and if individuals can increase their consumption of nutrient-rich foods, they will be able to meet their needs. “Many years of research have shown that it’s much better to get these nutrients from food for overall health,” she adds.

 “It’s hard to tease out individual nutrients from the diet. People with a healthier diet, with a good source of protein, fruits, and vegetables have healthier lifestyles. By eating a balanced, healthful diet, you’re getting micronutrients in the diet,” Schneider says.

This healthful eating pattern also applies to a moderate intake of other foods. For example, high levels of protein, caffeine, sodas, and sodium have been linked to calcium loss. “Many Americans consume too much protein, which can increase the urinary excretion of calcium, and this is of particular concern in a person with calcium intakes that are low,” Nieves says. “However, at older ages, protein intake is often too low, and this may lead to bone loss and fractures. In addition, there are reports that protein supplementation may help the healing of hip fractures,” she adds.

 “For protein, it’s important to have a balance. We should aim to have not too much but enough. This is true for everything,” Schneider says. She reports that caffeine doesn’t seem to promote calcium loss as long as there’s adequate calcium intake. However, if someone’s diet is high in sodium, Schneider says it can “pull calcium with it.”

Weight and Exercise
Maintaining a healthful weight through diet and physical activity are key strategies for preventing bone disease. “Osteoblasts come from stem cells. If you have physical activity and mechanical stress, stem cells make osteoblasts. If there’s inactivity, stem cells become adipocytes—fat cells. And we now know that fat isn’t inert; it has a lot of inflammatory factors that aren’t good for bone,” Schneider says.

“Physical activity is key to bone health, and the suggestion is to combine a program of weight-bearing activity, simply to carry the weight of your skeleton, such as walking; strength training to improve the muscles that support your skeleton; and exercises to improve your balance to prevent falls,” Nieves says.

When it comes to preserving bones, there’s a lot at stake, and dietitians have the skills to help their clients.

— Sharon Palmer, RD, is a contributing editor at Today’s Dietitian, a freelance food and nutrition writer in southern California, and the author of The Plant-Powered Diet.

 

References
1. Bone Health and Osteoporosis: A Report of the Surgeon General. Rockville, MD: US Department of Health and Human Services Office of the Surgeon General; 2004.

2. Learn about osteoporosis. National Osteoporosis Foundation website. http://www.nof.org/learn. Accessed October 15, 2012.

3. US Department of Agriculture, US Department of Health and Human Services. Dietary Guidelines for Americans, 2010. 7th ed. Washington, DC: US Government Printing Office; 2010.

4. NBHA reacts to media coverage regarding the US Preventive Services task force vitamin D and calcium supplementation to prevent cancer and osteoporotic fractures in adults draft recommendation statement. National Bone Health Alliance website. June 14, 2012. Accessed October 15, 2012.

5. Dietary supplement fact sheet: calcium. Office of Dietary Supplements website. http://ods.od.nih.gov/factsheets/Calcium-HealthProfessional. Accessed October 16, 2012.

6. Dietary reference intakes (DRIs): recommended dietary allowances and adequate intakes, vitamins. Institute of Medicine website. http://iom.edu/Activities/Nutrition/SummaryDRIs/~/media/Files/Activity Files/Nutrition/DRIs/RDA and AIs_Vitamin and Elements.pdf. Accessed October 16, 2012.

7. How much food from the dairy group is needed daily? ChooseMyPlate website. http://www.choosemyplate.gov/food-groups/dairy-amount.html. Accessed October 20, 2012.

8. Dietary supplement fact sheet: vitamin D. Office of Dietary Supplements website. http://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/. Accessed on October 18, 2012.

9. Anderson JJ, Roggenkamp KJ, Suchindran CM. Calcium intakes and femoral and lumbar bone density of elderly US men and women: National Health and Nutrition Examination Survey 2005-2006 analysis. J Clin Endocrinol Metab. 2012;97(12):4531-4539.

10. Giovannucci E, Rimm EB, Wolk A, et al. Calcium and fructose intake in relation to risk of prostate cancer. Cancer Res. 1998;58(3):442-447.

11. Vitamin D and calcium supplementation to prevent cancer and osteoporotic fractures. US Preventive Services Task Force website. http://www.uspreventiveservicestaskforce.org/uspstf12/vitamind/vitdfact.pdf. Accessed October 19, 2012.

12. Healthy eating plate. Harvard School of Public Health website. http://www.hsph.harvard.edu/nutritionsource/healthy-eating-plate. Accessed October 18, 2012.

13. Zhu LL, Cao J, Sun M, et al. Vitamin C prevents hypogonadal bone loss. PLoS ONE. 2012;7(10):e47058.

14. Dietary supplement fact sheet: magnesium. Office of Dietary Supplements website. http://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional. Accessed October 20, 2012.

15. Bügel S. Vitamin K and bone health in adult humans. Vitam Horm. 2008;78:393-416.

16. Fernández-Real JM, Bulló M, Moreno-Navarrete JM, et al. A Mediterranean Diet enriched with olive oil is associated with higher serum total osteocalcin levels in elderly men at high cardiovascular risk. J Clin Endocrinol Metab. 2012;97(10):3792-3798.

17. Weaver CM, Alekel DL, Ward WE, Ronis MJ. Flavonoid intake and bone health. J Nutr Gerontol Geriatr. 2012;31(3):239-253.

18. Tucker KL, Jugdaohsingh R, Powell JJ, et al. Effects of beer, wine, and liquor intakes on bone mineral density in older men and women. Am J Clin Nutr. 2009;89(4):1188-1196.