Kids and Their Bones (page 4)
Typically, when parents think about their children's health, they don't think about their bones. But building healthy bones by adopting healthy nutritional and lifestyle habits in childhood is important to help prevent osteoporosis and fractures later in life.
Osteoporosis, the disease that causes bones to become less dense and more prone to fractures, has been called “a pediatric disease with geriatric consequences,” because the bone mass attained in childhood and adolescence is an important determinant of lifelong skeletal health. The health habits your kids are forming now can make, or literally break, their bones as they age.
Why Is Childhood Such an Important Time for Bone Development?
Bones are the framework for your child's growing body. Bone is living tissue that changes constantly, with bits of old bone being removed and replaced by new bone. You can think of bone as a bank account, where (with your help) your kids make “deposits” and “withdrawals” of bone tissue. During childhood and adolescence, much more bone is deposited than withdrawn as the skeleton grows in both size and density.
For most people, the amount of bone tissue in the skeleton (known as bone mass) peaks by the late 20s. At that point, bones have reached their maximum strength and density. Up to 90 percent of peak bone mass is acquired by age 18 in girls and age 20 in boys, which makes youth the best time for your kids to "invest" in their bone health.
What Is Osteoporosis? Isn't It Something Old People Get?
Osteoporosis is a disease that causes bones to become fragile and break easily. When someone has osteoporosis, it means his/her “bank account” of bone tissue has dropped to a low level. If there is significant bone loss, even sneezing or bending over to tie a shoe can cause a bone in the spine to break. Hips, ribs, and wrist bones also break easily. The fractures from osteoporosis can be painful and disfiguring. There is no cure for the disease.
Osteoporosis is most common in older people but can also occur in young and middle-aged adults. Optimizing peak bone mass and developing lifelong healthy bone behaviors during youth are important ways to help prevent or minimize osteoporosis risk as an adult.
How Can I Help Keep My kids' Bones Healthy?
The same healthy habits that keep your kids going and growing will also benefit their bones. One of the best ways to encourage healthy habits in your children is to be a good role model yourself. Believe it or not, your kids are watching, and your habits, both good and bad, have a strong influence on theirs.
The two most important lifelong bone health habits to encourage now are proper nutrition and plenty of physical activity.
Eating for healthy bones means getting plenty of foods that are rich in calcium and vitamin D. Most kids get enough vitamin D from sunlight (or from foods like egg yolks or fortified milk), but most do not get enough calcium in their diets to help ensure optimal peak bone mass. Are your kids getting enough calcium?
Factors Affecting Peak Bone Mass
Peak bone mass is influenced by a variety of factors: some that you can't change, like gender and race, and some that you can, like nutrition and physical activity.
Gender: Bone mass or density is generally higher in men than in women. Before puberty, boys and girls develop bone mass at similar rates. After puberty, however, boys tend to acquire greater bone mass than girls.
Race: For reasons still not well understood, African American girls tend to achieve higher peak bone mass than Caucasian girls, and African American women are at lower risk for osteoporosis later in life. More research is needed to understand the differences in bone density between the various racial and ethnic groups. However, because all women, regardless of race, are at significant risk for osteoporosis, girls of all races need to build as much bone as possible to protect themselves against this disease.
Hormonal factors: Sex hormones, including estrogen and testosterone, are essential for the development of bone mass. Girls who start to menstruate at an early age typically have greater bone density. Those who frequently miss their menstrual periods sometimes have lower bone density.
Nutritional status: Calcium is an essential nutrient for bone health. In fact, calcium deficiencies in young people can account for a 5 to10 percent lower peak bone mass and may increase the risk for bone fracture in later life. A well-balanced diet including adequate amounts of vitamins and minerals such as magnesium, zinc, and vitamin D is also important for bone health.
Physical activity: Important for building healthy bones, physical activity provides benefits that are most pronounced in the areas of the skeleton that bear the most weight. These areas include the hips during walking and running and the arms during gymnastics and weight lifting.
Calcium is found in many foods, but the most common source is milk and other dairy products. Drinking one 8-oz glass of milk provides 300 mg (milligrams) of calcium, which is about one-third of the recommended intake for younger children and about one-fourth of the recommended intake for teens. In addition, milk supplies other minerals and vitamins needed by the body. The chart on the next page lists the calcium content for several high-calcium foods and beverages. Your kids need several servings of these foods each day to meet their need for calcium.
How Can I Persuade My Daughter to Drink Milk Instead of Diet Soda? She Thinks Milk Will Make Her Fat.
Soft drinks tend to displace calcium-rich beverages in the diets of many children and adolescents. In fact, research has shown that girls who drink soft drinks consume much less calcium than those who do not.
It's important for your daughter to know that good sources of calcium don't have to be fattening. Skim milk, low-fat cheeses and yogurt, calcium-fortified juices and cereals, and green leafy vegetables can all fit easily into a healthy, low-fat diet. Replacing even one soda each day with milk or a milk-based fruit smoothie can significantly increase her calcium intake.
Selected Food Sources of Calcium
|Food||Calcium (mg)||% DV *|
|Sardines, canned in oil, with bones, 3 oz.||324||32%|
|Cheddar cheese, 1 1/2 oz., shredded||306||31%|
|Milk, nonfat, 8 fl oz.||302||30%|
|Yogurt, plain, low fat, 8 oz.||300||30%|
|Milk, reduced fat (2% milk fat), no solids, 8 fl oz.||297||30%|
|Milk, whole (3.25% milk fat), 8 fl oz.||291||29%|
|Milk, buttermilk, 8 fl oz.||285||29%|
|Milk, lactose reduced, 8 fl oz.
(content varies slightly according to fat content; average=300 mg)
|285 – 302||29 – 30%|
|Cottage cheese, 1% milk fat, 2 cups unpacked||276||28%|
|Mozarella, part skim, 1 ½ oz.||275||28%|
|Tofu, firm, with calcium, ½ cup**||204||20%|
|Orange juice, calcium fortified, 6 fl oz.||200 – 260||20 – 26%|
|Salmon, pink, canned, solids with bone, 3 oz.||181||18%|
|Pudding, chocolate, instant, made with 2% milk, ½ cup||153||15%|
|Tofu, soft, with calcium, ½ cup**||138||14%|
|Breakfast drink, orange flavor, powder prepared with water, 8 fl oz.||133||13%|
|Frozen yogurt, vanilla, soft serve, ½ cup||103||10%|
|Ready to eat cereal, calcium fortified, 1 cup||100 – 1000||10 – 100%|
|Turnip greens, boiled, ½ cup||99||10%|
|Kale, raw, 1 cup||90||9%|
|Kale, cooked, 1 cup||94||9%|
|Ice cream, vanilla, ½ cup||85||8.5%|
|Soy beverage, calcium fortified, 8 fl oz.||80 – 500||8 – 50%|
|Chinese cabbage, raw, 1 cup||74||7%|
|Tortilla, corn, ready to bake/fry, 1 medium||42||4%|
|Tortilla, flour, ready to bake/fry, one 6" diameter||37||4%|
|Sour cream, reduced fat, cultured, 2 tbsp||32||3%|
|Bread, white, 1 oz.||31||3%|
|Broccoli, raw, ½ cup||21||2%|
|Bread, whole wheat, 1 slice||20||2%|
|Cheese, cream, regular, 1 tbsp||12||1%|
Source: USDA 2002, Heaney et al 2000.
* DV=Daily Value
* * Calcium values are only for tofu processed with a calcium salt. Tofu processed with a non-calcium salt will not contain significant amounts of calcium.
But my kids don't like milk.
Drinking milk isn't the only way to enjoy its benefits. For example, try making soup and oatmeal or other hot cereals with milk instead of water. Pour milk over cold cereal for breakfast or a snack. Incorporate milk into a fruit smoothie or milkshake. Chocolate milk and cocoa made with milk are also ways to increase the milk in your child's diet.
Sources of calcium also might include an ounce or two of cheese on pizza or a cheeseburger, a cup of calcium-enriched orange juice, or a small carton of yogurt. Your kids can also get calcium from dark green, leafy vegetables like kale or bok choy, or foods such as broccoli, almonds, tortillas, or tofu made with calcium. Many popular foods such as cereals, breads, and juices now have calcium added too. Check the Nutrition Facts label on the package to be sure.
My Teenage Son Loves Milk, But It Seems to Upset His Stomach. Could He Have Lactose Intolerance?
People with lactose intolerance have trouble digesting lactose, the sugar found in milk and dairy foods. Lactose intolerance is not common among infants and young children, but can occur in older children, adolescents, and adults. It is more common among people of African American, Hispanic, Asian, and American Indian descent.
Most kids with lactose intolerance are able to digest milk when it is served in small amounts, and combined with other foods like cereal. They may tolerate other dairy products such as cheese or yogurt even if milk is a problem. Lactose-free milk products are now available in most stores, and there are pills and drops you can add to milk and dairy products that make them easier to digest.
Be sure to include plenty of foods with calcium in the meals and snacks you plan for your kids. Almonds, calcium-fortified orange juice, tortillas, fortified cereals, soy beverages, and broccoli with dip are a few great choices. While it's best to get calcium from food, calcium supplements can also be helpful.
How to Read a Food Label for Calcium
The food label, called Nutrition Facts, shows you how much one serving of that food contributes to the total amount of calcium, as well as other nutrients, you need every day. This is expressed as a percent of the daily value (%DV) of calcium that is recommended. For labeling purposes, this is based on the daily calcium recommendation of 1,000 milligrams for people 19 to 50 years old. Since children and teens 9 to 18 years old require more calcium, their %DV target is higher, as indicated below:
|Age||Recommended calcium intake||%DV target|
|9 – 18||1,300 mg||130%DV|
|19 – 50||1,000 mg||100%DV|
Here is an easy rule of thumb for evaluating the calcium content of a food: 20%DV or more is high for calcium. That means it is a high-calcium food and contributes a lot of calcium to the diet. A food with a calcium content of 5%DV or lower contributes little calcium to the diet and is a low source.
If you want to convert the %DV for calcium into milligrams, you can multiply by 10. For example, if a single-serve container of yogurt lists 30%DV for calcium, it contains 300 mg of calcium (30% times 10).
Getting plenty of high-calcium foods every day is important. To meet their calcium needs, children 9 to 18 years old need about four servings of foods with a 30%DV for calcium (300 mg each) or six to seven servings of foods with a 20%DV for calcium (200 mg each) every day. Foods with a lower %DV for calcium are also important to fill gaps and help ensure that your children get all the calcium they need.
My Daughter Is Constantly Dieting. Should I Be Concerned?
Maintaining proper weight is important to overall health, but so is good nutrition. If your daughter is avoiding all milk and dairy products and severely restricting her food intake, she is probably not getting enough calcium. She needs a more balanced diet that includes low-fat milk products and other calcium-rich foods. Calcium supplements may also be helpful to ensure that she gets enough of this essential nutrient.
You should discuss your concerns with your daughter's doctor. If your daughter is one of up to 3 percent of American girls and young women with eating disorders, the problem is even more serious. Eating disorders, especially anorexia nervosa, can lead to missed or irregular menstrual periods or the complete absence of periods, known as amenorrhea. These are signs of low estrogen, a hormone that is essential for developing bone density and reaching peak bone mass. Girls with anorexia nervosa will often have fractures as a first sign of the disease. Furthermore, reduction in estrogen production in adolescence can increase your daughter's risk of osteoporosis and fracture later in life. In severe cases, girls with eating disorders may even develop osteoporosis in their 20s, and they may find the damage to their bones cannot be reversed later in life.
Look for the following signs and see your daughter's physician if you think your daughter has, or is at risk of developing, an eating disorder:
- missed menstrual periods after having had them regularly for at least several months
- extreme and/or unhealthy-looking thinness
- extreme or rapid weight loss
- frequent dieting practices such as
- eating very little
- not eating in front of others
- trips to the bathroom following meals
- preoccupation with thinness
- focus on low-calorie and diet foods
- overtraining or excessive exercise
Should I Give My Kids Calcium Supplements?
Experts believe calcium should come from food sources whenever possible. However, if you think your children are not getting adequate calcium from their diet, you may want to consider a calcium supplement. For optimal absorption, no more than 500 mg of calcium should be taken at one time.
How Does Physical Activity Help My Kids' Bones?
Muscles get stronger when we use them. The same idea applies to bones: the more work they do, the stronger they get. Any kind of physical exercise is great for your kids, but the best ones for their bones are weight-bearing activities like walking, running, hiking, dancing, tennis, basketball, gymnastics, and soccer. (Children who tend to play outside will also have higher vitamin D levels.) Swimming and bicycling promote your kids' general health, but are not weight-bearing exercises and will not help build bone density. Organized sports can be fun and build confidence, but they are not the only way to build healthy bones.
The most important thing is for your kids to spend less time sitting and more time on their feet and moving. Alone or with friends, at home or at the park, one of the best gifts you can give your kids is a lifelong love of physical activity.
Bone Building Activities
- Ice hockey/field hockey
- In-line skating
- Lifting Weights
- Jumping rope
Is It Possible to Get Too Much Exercise?
For most people, including children and teens, the challenge is to get enough physical activity. However, excessive exercise and overtraining, often coupled with restrictive eating, can be a problem, especially for some female athletes and dancers, as well as girls who become obsessive about weight loss. Overtraining, like eating disorders, can result in decreased estrogen and eventually lead to thin bones that break easily.
Years ago, it was not unusual for coaches and trainers to encourage athletes to be as thin as possible for many sports, including dancing, gymnastics, figure skating, running, and diving. Fortunately, many coaches now realize that being too thin is unhealthy and can negatively affect performance as well as lifelong health.
Reprinted with the permission of the National Institute of Mental Health. © 2008 NIMH.
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