If a child comes to Childrens Hospital Los Angeles with a bone problem, the shout immediately goes out: ?Call Dr. Duke!? That is the nickname for Pisit Pitukcheewanont, M.D., assistant professor of pediatrics at the Keck School of Medicine of USC and clinical director of the pediatric bone program in CHLA?s endocrinology division. These days, many are getting to know ?Dr. Duke? because of his talks in the community on behalf of kids? bone health. Pitukcheewanont wants to spread the word: Lifestyle habits that children have today can either strengthen or hinder the bones they end up with in adulthood. But with a little effort and smart choices, kids? bones can grow to be all they can be. Bone bank Children?s bones grow in stages. As children grow up, from babyhood to just before puberty, their bones grow longer, wider and thicker, with boys? bones growing bigger than girls? bones. In puberty, hormones surge and influence bone growth. During these teen years, bones not only keep growing larger, but they also grow denser. Bone growth peaks in the late teens and early 20s, when bones are at their very strongest. It levels out until the early 30s, when bones start losing mass and density. ?If anything interferes with bone growth during childhood, you?re going to have a problem,? he says. For some children, diseases and medications are to blame for bone problems; but others have no such underlying causes. ?About a third of children will suffer a fracture of some kind between birth and age 16,? Pitukcheewanont says, ?and a third of these fractures are not related to a high-impact trauma.? If a seemingly innocuous tap fractures a bone, that indicates a weakness in the bones themselves, he explains. ?That suggests to us that the child has low bone mass or an increased risk of osteoporosis later in life.? Studies show that healthy children who have the smallest and least dense bones when they start puberty, at about age 10, will still have the smallest and least dense bones when they stop growing at age 18. And those who have the biggest bones as 10-year-olds also end up with the biggest bones at 18. Bone built up by the late teens or early adulthood forms a sort of lifetime ?bone bank.? During adulthood, the body slowly withdraws bone from the bank. The less bone to start with, the likelier bone will become porous and vulnerable to fracture. Genetics accounts for as much as 60 to 80 percent of bone structure. The other 20 to 40 percent is where actions can make a difference. Got calcium? Because bones are mostly made of calcium, the body needs calcium to build bones. But all other cells in the body need the mineral to function, too, so when the body does not get enough calcium through food, it takes calcium out of bones. Kids ages 9 to 17 need about 1,300 milligrams (mg) of calcium a day, and those between ages 3 and 8 need 800 mg a day, according to the Institute of Medicine. Milk is the best dietary calcium source, Pitukcheewanont says. Eight ounces of milk?a cup?contains about 300 mg of calcium. For kids who have difficulty digesting lactose, good options include tofu, some cheeses and yogurt, as well as soy and rice milk. ?Vegetarians can get calcium from green, leafy vegetables, too,? he adds. ?But to make up the same amount that you?d get from a cup of milk, you?d need a whole lot of vegetables.? It takes eight cups of spinach, for example, to get the same calcium as one cup of milk. Today, kids are not drinking enough milk, physicians say. They often displace the drink with sweet juices or soda. Teenage girls are especially at risk: less than one quarter of these girls get the calcium they need each day, according to the National Institutes of Health. ?I?ll ask them why they don?t drink milk, and I hear, ‘I can’t handle it: It tastes nasty,’? he says. He recommends milk with 2 percent fat, and notes physicians no longer recommend whole milk, since obesity is a growing problem among children. At his bone clinic, Pitukcheewanont provides guides for parents on foods rich in calcium and other nutrients and sends kids with bone problems to a dietitian, who can strategize with families on increasing calcium intake. Vitamin D dilemma Consuming calcium alone is not enough, though. To absorb calcium from the intestines into the blood stream, the body needs vitamin D. Fortunately, vitamin D comes from sunlight. Kids who spend 20 to 30 minutes in mid-day sunlight three times a week usually get enough vitamin D?400 international units a day?through their skin. Problems can arise in regions where children get less sun exposure, when children stay indoors all the time or if parents slather high-SPF sunblock on their children so thoroughly that ultraviolet light cannot reach the skin. Sunblock is beneficial for preventing skin cancer, but if a child goes outside for prolonged sun exposure, Pitukcheewanont suggests parents might opt to wait for 15 minutes before applying lotion so that at least some sunlight reaches the skin. Children can also get vitamin D through diet. Parents should check nutritional information on milk cartons to make sure the milk contains the vitamin, he says. Multivitamin supplements also can help. Pop and fizzle One of kids’ common habits, though, might interfere with vitamin D’s work. ?Today, kids are trading milk for soda,? explains endocrinologist Robert Rude, M.D., professor of medicine at the Keck School and specialist in osteoporosis and bone and mineral metabolism. Teenage boys and girls today drink twice as much soda as milk. Yet only two decades ago, they drank twice as much milk as soda, according to the Center for Science in the Public Interest. Researchers have found that when kids eat lots of sugary and carbohydrate-laden foods and drinks, the rest of their diet misses key nutrients. But the implications do not stop there. One of the problems might lie in the phosphoric acid common in soft drinks. Rude and Pitukcheewanont explain that excessive phosphorus appears linked to bone loss. The amount of calcium in the diet should outweigh phosphorus, but phosphorus now outpaces calcium, they say. American adults, for example, are getting between 1,500 mg and 2,000 mg of phosphorus a day, when they should only consume about 700 mg, Rude says. Among children, soda, preservatives and fast foods supply lots of phosphorus too. Pitukcheewanont explains that excess phosphorus intake is thought to hamper the kidneys from processing active vitamin D that the body needs to absorb calcium into the blood. So even if these kids eat more calcium, their bodies are hindered from using it. Excessive caffeine appears to play a role in bone troubles, too, by causing the body to eliminate calcium through the urine, Pitukcheewanont says. Among diabetic children, soda’s sugar can cause them to excrete calcium, too. ?I wouldn’t say kids should never have soda,? he concludes, ?but having it in moderation is a good idea.? Bone building To become strong, the bones themselves must do some work. They need what physicians call weight-bearing activity, which makes the bones and muscles labor against gravity. Because bones are made of living cells, the work they must do to support the body during exercise actually stimulates more new bone tissue to form. The activity also makes muscles grow stronger so they tug and pull harder against the bones, challenging them to grow even more. Playing tag, soccer, tennis and basketball, dancing and jogging are just a few weight-bearing activities kids can enjoy. Overweight children who feel uncomfortable exercising can start out by walking. If they want to try lifting weights, Pitukcheewanont warns that the activity must be managed carefully to avoid hurting cartilage. And although swimming provides great cardiovascular benefits, it does not help bones much. He suggests kids participate in different types of activity to benefit their bones and heart?as well as to maintain a healthy weight. Body image Lifelong athletes develop and maintain greater bone mass than others, says Rude. But some teens can take it too far. Teenage girls who exercise excessively?whether it is running, bicycling or any other activity?and do not eat enough calories can experience amenorrhea. This means that the estrogen that should be coursing through their bodies, helping them develop into adults, declines so much that they stop menstruating. An eating disorder, such as anorexia nervosa, also can cause estrogen deficiency. Estrogen, explains Pitukcheewanont, pushes girls’ bones to grow denser during the teens, just as testosterone does in boys. When estrogen is too low, girls’ bones cannot grow as dense as they should. Girls may then develop osteoporosis during their teen years and as young adults, falling victim to painful bone fractures. Body image and the quest for thinness can cause girls to shy away from dairy foods they fear might make them fat. And smoking?which may be seen as a way to stay thin?harms more than just bone health. So does drinking alcohol. Pitukcheewanont sees simple improvements in lifestyle, from diet to exercise, as the key to making the most of the bone potential that kids have hidden inside of them. ?I don’t think that I can cure osteoporosis, so I don’t expect that,? he says. ?But I’d like to be able to improve the quality of bone in kids and adolescents so they can achieve their peak bone mass.?- � RELATED ARTICLES what’s the buzz? -Someday, a daily prescription for kids’ healthy bones might include 10 minutes atop a vibrating platform. Pisit Pitukcheewanont, M.D., clinical director of the pediatric bone program in Childrens Hospital Los Angeles’ endocrinology division, is participating in tests of what he calls ?The Jiggler,? a mechanical stimulator that appears to strengthen bones. The one-square-foot plastic platform sits atop a series of springs. Scientists first tested it with sheep and turkeys, Pitukcheewanont says, ?and it was found to significantly improve their bone density.? It also recently was tested with postmenopausal women, and results suggested it might reduce bone loss. The device’s creator, Clinton Rubin, Ph.D., a biomedical engineer at the State University of New York at Stony Brook, contacted Vicente Gilsanz, M.D., Ph.D., Keck School professor of radiology, Pitukcheewanont and their CHLA colleagues to explore the platform’s utility in actually building bone, not just maintaining it, in children. Early tests were encouraging, Pitukcheewanont says, so they plan a larger study. The platform vibrates so quickly and gently it does not even seem as though it is moving. While weight-bearing exercise sends powerful forces through bone at a low frequency?the pace of a jogger running on a track, for example?the platform seeks to send small forces (one-third that of gravity) through bone, but at high frequency (30 cycles per second). Says Pitukcheewanont: “We hope this works, because it would be a great tool in the future.”
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