Healthy Bones, Calcium, Vitamin D

	There are 206 bones in the human body and the skeleton comprises 20 percent of total body weigh¹. The human skeleton is strong, yet light, and almost perfectly adapted for the movement, protection and manipulative functions it performs. Maintaining strong, healthy bones can be accomplished by getting the recommended amount of calcium daily, being physically active and maintaining body weight in the normal weight range. Kids/Teen Fractures Fracture incidence has increased by one-third in boys and one-half in girls compared to a generation ago². This can be attributed to the large increase in childhood obesity, replacement of milk with other beverages such as soda and juice and a decrease in physical activity due to increased “screen time” such as playing video games or being on the computer. Dietary calcium, a key nutrient in milk, has been shown to be a major factor associated with fracture risk; the greater the calcium intake, the lower the risk of fracture. Physical activity is another key determinant in bone health. Physical activity is one of the few ways the body builds up bone density, so when children are inactive their bones become weaker. Activities that are specifically good for bone health include weight-bearing activities such as jogging, walking and dancing. Teens can assess their level of physical activity by completing the Teen BEAT, Basic Exercise & Activity Tracker. During the teenage and young-adult years, it is important to achieve the highest peak bone mass possible to reduce the likelihood of developing osteoporosis later in life. Peak bone mass is attained at about 30 years of age; however, the biggest impact on total bone mass is determined during adolescence. Calcium is best absorbed into bones at around age 12 for girls and age 14 for boys. During the years of rapid growth during adolescence, 40 percent of total lifetime bone mass is accumulated. Research shows that adequate calcium intake is critical for achieving peak bone mass and also modifies the rate of bone loss associated with aging. Calcium intake in early life may account for as much as a 5 percent to 10 percent difference in peak adult bone mass, which may contribute to a 50 percent difference in the hip fracture rate later in life. Although other foods such as broccoli, mustard greens and almonds contain calcium, the best sources of calcium in the Western diet are milk and dairy foods. Unfortunately, dietary intake surveys repeatedly show that many children fail to meet the dietary recommendations for calcium. Nine out of ten girls aged 12 – 19 and seven out of ten boys do not consume adequate calcium in their diet. According to a study published 2008 in Bone, children who had inadequate calcium consumption prior to the start of these studies experienced a substantial increase in their total body bone mineral content (BMC) that was approximately 25 times greater than children who already consumed adequate amounts of calcium. These improvements in bone mineral content were achieved when calcium intake was increased to the amounts recommended in the Dietary Guidelines³. Parents—Be Your Child’s Partner in Healthy Bones offers realistic suggestions for increasing calcium in the diet during these critical years. Research also shows that overweight children experience more fractures than normal-weight children, and children who have a fracture at an early age have a higher rate of repeat fractures.⁴ A case-control study in boys aged 3 to 19 years found that high adiposity and low bone-mineral content were associated with increased risk of forearm fractures.⁵ Another study found that high body weight contributes to fracture risk in children and adolescents who fracture their forearms repeatedly. Body weight may contribute to fracture risk by placing extra burden on bones during falls. Lack of physical activity—common in overweight children—may also play a role in fracture risk, as physical activity is associated with stronger bones. The younger a child gets his or her first fracture, the more likely it is that he or she will have reoccurring fractures. Children who consume three cups of milk and dairy foods daily and are physically active for one hour on most days are likely to maintain strong bones and good health.⁶

	Osteoporosis Osteoporosis is a bone disease common in older adults, marked by lower than normal bone mineral levels that lead to increased fracture risk. This disease affects millions of Americans every year, especially women. Women are twice as likely to develop osteoporosis as men due to the sudden drop in estrogen at menopause and their tendency to live longer. Some other risk factors for osteoporosis are: smoking, old age, ethnicity (whites or Asians have a higher risk than blacks or Hispanics), family history, being very thin, early menstruation and/or late menopause, eating disorders, alcoholism, excess caffeine, low calcium intake and a sedentary lifestyle.⁷ Keeping calcium levels high, making physical activity a habit and trying to avoid the risk factors that can be avoided (such as smoking or drinking) is a good way to prevent the disease. Calcium intake in early life may contribute to a 50 percent difference in the hip fracture rate later in life.⁸
	Vitamin D Vitamin D is often referred to as the "sunshine" vitamin because our bodies can make it when our skin is exposed to the sun. About 10 to 15 minutes of sun exposure per day on our face, hands and arms—without sunscreen—is enough to meet our needs. For children and adults up to age 50, 200 International Units (IU) is the recommended amount of vitamin D per day. With age, we lose some ability to make the vitamin from sunlight exposure and to turn it into its active form, so the recommendation increases to 400 IU per day for those aged 51-70 years, and to 600 IU for those older than 70. In these latter groups, supplements may be needed to reach recommended intake levels. Vitamin D is essential to good health because it helps with dietary absorption of calcium. New research has found a link between vitamin D and preventing various cancers and other diseases. Deficiency in vitamin D in children will cause rickets and in older adults could cause muscle weakness that may lead to falls. Studies suggest that having enough vitamin D increases cognitive performance, immune function and protects against periodontal disease that can lead to tooth loss.
	More about vitamin D: Vitamin D: What You Need to Know About the Sunshine Vitamin. Return to Dairy Facts Overview page.

	¹Khosla S et al. JAMA 2003;17;290(11):1479-85. ²Kranz S et al. J Pediatr 2007; 151(6) 642-6. ³Huncharek M, et al. Bone 2008; 43(2):219-410. ⁴Taylor et al. Pediatrics 2006;117(6):2167-2174. ⁵Goulding A et al. J Bone Miner Res 2005;20(12):2090-6. ⁶Dietary Guidelines for Americans 2005, 6th ed. 2005: www.healthierus.gov/dietaryguidelines. ⁷Mayo Clinic (2007) Osteoporosis risk factors. Retrieved Aug 13, 2008, from Mayo Clinic website: http://www.mayoclinic.com/health/osteoporosis/DS00128/DSECTION=risk-factors. ⁸Bligh M et al. (2008) Bone health for children and adults: Implications for counseling. Retrieved Aug 13, 2008, Dairy Council of California website: http://www.dairycouncilofca.org/HealthProfessionals/BoneHealthCourse/BH_online.aspx..