May 2011 Issue
Best Defense — Early Exercise and Proper Nutrition Can Help Prevent Later Osteoporosis
By Densie Webb, PhD, RD
Vol. 13 No. 5 P. 14
May is National Osteoporosis Awareness and Prevention Month, established to increase education about and awareness of this bone-deteriorating condition. While osteoporosis is generally considered to be a problem that plagues older people, the most critical time for preventing the condition is in childhood and adolescence. Knowing the facts will prepare you to better counsel patients, clients, and their children about lifelong bone health.
Of the 10 million people affected by osteoporosis, 80% are women, according to the National Osteoporosis Foundation. The number of afflicted people is expected to increase to 14 million by 2020. The foundation says another 34 million people have low bone mass, putting them at risk of fractures. It’s important to make sure children take ongoing steps toward preventing osteoporosis so they can reduce the impact the disease may have in later life.
During the years of peak skeletal growth, teenagers accumulate more than 25% of adult bone.1 It’s an unfortunate reality that dietary habits tend to take a nosedive during these years, as fast food often replaces more nutritious meals at home and sodas replace calcium- and vitamin-D-rich milk. There is evidence that fractures in children have increased over the last four decades.2 Whether that is a result of changes in childhood activities or a decline in the quality of children’s diets, or both, isn’t known.
Higher calcium intakes increase bone mineral density in children and adolescents.3 However, calcium intakes in U.S. children often fall short of recommendations and tend to decrease even more during the preteen and adolescent years.4 National Health and Nutrition Examination Survey data from 2007-2008 found that for boys between the ages of 6 and 19, calcium intake ranged from an average of 1,034 mg to 1,173 mg per day. For girls in the same age group, intake ranged from only 878 mg to 885 mg per day, with older girls consuming less than younger girls. The recently updated Institute of Medicine recommendations for calcium established a Recommended Dietary Allowance of 1,000 mg/day for boys and girls aged 4 to 8 and 1,300 mg/day for those aged 9 to 18. Girls, who are most at risk, have the largest gap between these calcium recommendations and intake.
The American Academy of Pediatrics recommends consuming three 8-oz glasses of low-fat milk per day (or the equivalent) for children aged 4 to 8 to achieve the recommended adequate intake of calcium and vitamin D and four 8- to 10-oz glasses of milk (or the equivalent) for adolescents. A Harvard study found that among boys and girls aged 9 to 18, recommended intakes for calcium could not be met with dairy-free diets.5 The researchers suggested calcium-fortified foods to fill in the calcium gap. Calcium supplements are the next best option for children and adolescents who can’t or don’t consume dairy foods.
While calcium and vitamin D are the primary nutrients of concern for achieving good bone health in children, other nutrients such as zinc, magnesium, and phosphorus also play important roles. However, according to Emma Laing, PhD, RD, LD, an assistant research scientist in the Bone & Body Composition Laboratory at the University of Georgia, there are few studies that have looked at the roles these other nutrients play in the bone health of children and adolescents. “Our lab is currently looking at zinc and others are studying phosphorus, magnesium, potassium, and vitamin K,” she says.
Physical Activity’s Role in Building Bone
While calcium and vitamin D intakes are important, it’s becoming increasingly clear that the combination of adequate nutrient intake and regular vigorous physical activity is key to good bone health as an adult. A U.K. study looked at a group of boys and girls aged 8 to 11 and evaluated their calcium intakes and levels of physical activity.6 Researchers found that children who engaged in 25 to 40 minutes of vigorous activity per day, such as running, playing tag, and jumping rope, and who consumed at least 700 to 800 mg of calcium per day built and retained the greatest bone mass. The study also suggested that the lower a child’s calcium intake, the more important regular vigorous physical activity becomes.
A University of Iowa study suggests that the often-cited “window of opportunity” for building peak bone mass may begin even earlier than previously thought—as early as 5 years old.7 The study, which looked at young children and their physical activity and bone mineral content, found that those with the highest levels of moderate and vigorous physical activity at age 5 accumulated between 4% and 14% more bone mineral content at ages 8 and 11 than those with the lowest levels of physical activity.
“The higher the impact, the greater the benefit and the less time needed to incur benefits,” says Kathleen Janz, EdD, a researcher on the study.
Volleyball ranked as the activity with the greatest benefit, followed by jogging. Cycling and swimming ranked as two activities with the least benefit for bone. For bone health, Janz recommends that children accumulate 60 minutes of daily physical activity, including at least 20 to 30 minutes of vigorous activity.
Six Counseling Tips for Saving Bone
Gathered from a variety of expert sources, these tips are key to osteoporosis prevention that begins in childhood and adolescence:
1. Ensure that children and adolescents obtain an adequate calcium and vitamin D intake. Foods are best, followed by fortified foods and supplements (in that order).
2. Recommend an overall healthful diet that includes fruits, vegetable, whole grains, lean meats, and low-fat dairy to ensure adequate intake of other vitamins and minerals critical for bone development.
3. Encourage children to take part in a total of 60 minutes of physical activity every day; 20 to 30 minutes of that should be vigorous, high-impact activity such as running, jumping rope, and sports such as soccer.
4. Discourage smoking, which is associated with low bone mass. According to the Centers for Disease Control and Prevention (CDC), almost one-half of all high school students have tried smoking.
5. Discourage drinking, which is associated with low bone mass. According to the CDC, almost one-quarter of high school students had five or more alcoholic drinks in a row within the 30 days prior to being surveyed.
6. Be alert to extreme dieting measures, which can lead to undernutrition and negatively impact bone health.
— Densie Webb, PhD, RD, is a freelance writer, editor, and industry consultant based in Austin, Tex.
Extra Help for Girls
Best Bones Forever (BFF) is a national bone health campaign from the Health and Human Services Office on Women’s Health aimed at improving bone health in girls aged 9 to 14. The colorful site includes quizzes and easy-to-prepare, kid-friendly recipes. The section for parents provides a wealth of information and tips—from a bone-healthy grocery list to bone-building family activities.
1. Bailey DA, Martin AD, McKay HA, Whiting S, Mirwald R. Calcium accretion in girls and boys during puberty: A longitudinal analysis. J Bone Miner Res. 2000;15(11):2245-2250.
2. Khosla S, Melton LJ 3rd, Dekutoski MB, Achenbach SJ, Oberg AL, Riggs BL. Incidence of childhood distal forearm fractures over 30 years: A population-based study. JAMA. 2003;290(11):1479-1485.
3. Wosje KS, Specker BL. Role of calcium in bone health during childhood. Nutr Rev. 2000;58(9):253-268.
4. Keller KL, Kirzner J, Pietrobelli A, St-Onge MP, Faith MS. Increased sweetened beverage intake is associated with reduced milk and calcium intake in 3- to 7-year old children at multi-item laboratory lunches. J Am Diet Assoc. 2009;109(3):497-501.
5. Gao X, Wilde PE, Lichtenstein AH, Tucker KL. Meeting adequate intake for dietary calcium without dairy foods in adolescents aged 9 to 18 years (National Health and Nutrition Examination Survey 2001-2002). J Am Diet Assoc. 2006;106(11):1759-1765.
6. Rowlands AV, Ingledew DK, Powell SM, Eston RG. Interactive effects of habitual physical activity and calcium intake on bone density in boys and girls. J Appl Physiol. 2004;97(4):1203-1208.
7. Janz KF, Letuchy EM, Eichenberger Gilmore JM, et al. Early physical activity provides sustained bone health benefits later in childhood. Med Sci Sports Exerc. 2010;42(6):1072-1078.