Bone is a living tissue that changes throughout our lives, as the body breaks down old bone and forms new bone. The most important time for building a strong skeleton is during childhood and adolescence.
The greatest gains in bone size and strength occur in adolescence, when the hormones of puberty speed up bone growth. Bones not only get longer and wider, they also get denser (thicker). People reach their peak bone mass—their largest and densest bone— by their late teens or early twenties. As early as age 30, some bones begin to slowly lose mass as a normal part of aging.
The more bone mass we “bank” in childhood and adolescence, the better protected we are from the bone loss that can lead to osteoporosis (thin, fragile bones) and bone fractures later in life.
The genes we inherit, our hormones, and our lifestyle all affect our peak bone mass. Genetic factors have the greatest influence on peak bone mass. To reach his or her full “genetic potential,” a child needs the right amount of certain hormones, along with healthy eating and exercise habits.
Growth hormone and the sex hormones estrogen and testosterone at puberty are essential for building bone mass in both boys and girls. Maintaining a healthy weight and getting enough vitamin D, calcium, protein, and physical activity are also important to bone health. Calcium is the main building block of strong, healthy bones, and vitamin D helps the body absorb calcium. Other minerals, (i.e. phosphorus and magnesium) and micronutrients in amounts that are found in a healthy diet are also important in building healthy bone. Weight-bearing exercise, such as running and jumping, helps build muscle and bone strength. Having well developed muscles is important to build strong bones. The "pull" that the muscles exert on the bones increase signals in the bones themselves that allow them to become stronger over time.
Boys usually reach a higher peak bone mass than girls. When compared to girls, they are less likely to develop osteoporosis as they age. To build as much bone strength as they can, adolescent girls and boys need to be careful in their approach to diet and exercise. Menstruation can stop in girls who exercise too much or are extremely underweight (as in anorexia). Girls who never start their periods or stop menstruating often have low estrogen levels, which can harm their bone health. Underweight boys or boys with delayed puberty can also have hormone changes that affect accumulation of bone mass.
If your child has had certain fractures, your child’s bone mass can be evaluated by an X-ray exam called a DXA scan or Bone Mineral Density (BMD) test.
Vitamin D. Most of our vitamin D is produced when our skin is exposed to sunlight. Children get vitamin D from playing outdoors in the sun. Our bodies' ability to make vitamin D changes based on our location, the season of the year, time of day and whether we are wearing sunscreen or sun blocking clothing. Sunscreens block the sun’s rays that cause our bodies to make vitamin D.
We also get some vitamin D from food, but very few foods naturally contain vitamin D. In the United States, most milk, infant formulas, and some cereals are fortified (meaning vitamin D is added).
Infants need at least 400 IU (international units) of vitamin D each day. Breast-fed babies should get vitamin D supplements since mother’s milk is low in vitamin D; another option is for the mother to take high-dose vitamin D supplement. Children and adolescents need at least 600 IU of vitamin D daily.
Children and adolescents with dark skin, limited sun exposure, obesity, or certain chronic diseases are more likely to be deficient in vitamin D. These children may need more than 600 IU to reach a healthy vitamin D level. A simple blood test can check for vitamin D deficiency. This test is recommended only for children who have risk factors for poor bone health.
Calcium. The recommended daily calcium intake for children and adolescents varies by age:
|0–6 months||7–12 months||1–3 years||4–8 years||9–18 years|
|210 milligrams (mg)||270 mg||500 mg||800 mg||1,300 mg|
** The quantities in this table can come from diet or supplements.
You can set an example for your child by modeling good bone health habits. Keep calcium-rich foods on hand and encourage physical activity, especially outdoor (with skin safety in mind) to get healthy Vitamin D levels. Talk about your child’s bone health whenever you consult your pediatrician.