Most people think osteoporosis (loss of bone mass) is a disease of the elderly. However, although people normally lose bone mass as they age, the amount of bone growth that occurs during childhood and adolescence is just as important a factor in developing osteoporosis. That's what experts at the National Institutes of Health (NIH) said at a conference on Osteoporosis Prevention, Diagnosis and Therapy in March 2000.

Bones grow in size during childhood, gaining mass and strength. The amount of bone mass you obtain while you are young determines your skeletal health for the rest of your life. The more bone mass you have after adolescence, the more protection you have against losing bone mass later.

Childhood is critical for developing lifestyle habits that support good bone health. Cigarette smoking often starts in childhood. It has a harmful effect on reaching peak bone mass.

Good nutrition is vital for normal growth. Like all tissues, bone needs a balanced diet, enough calories, and appropriate nutrients, such as calcium. But not everyone follows a diet that is best for bone health. For example, the federal government's Institute of Medicine recommends a calcium intake for children ages 9 to 17 years of 1,300 mg/day (800 mg/day for children ages 3 to 8 years). However, only about 25% of boys and 10% of girls in this age group have a diet that meets these recommendations.

Calcium is the most important nutrient for reaching peak bone mass. It prevents and treats osteoporosis. The body requires vitamin D to absorb calcium effectively. Most infants and young children in the United States get enough vitamin D from fortified milk. But adolescents don't consume as many dairy products. They may not get adequate levels of vitamin D. Dieting and fasting to be thin may harm nutrition and bone health. Teens who diet may need to take calcium and vitamin D supplements.

Several groups of children and adolescents are at risk for poor bone health, including:

• Premature infants and infants with low birth weight who have lower than expected bone mass in the first few months of life.
• Children who take medications such as steroids to treat respiratory diseases such as asthma.
• Children who have cystic fibrosis, celiac disease, and inflammatory bowel disease. These conditions make it difficult for the body to absorb nutrients appropriately.
• Adolescent girls who have minimal, delayed or irregular menstrual cycles because of strenuous athletic training, emotional stress, or low body weight.
• Children with cerebral palsy and other conditions that place limits on physical activity, especially those who take chronic medications for seizure control.

Many more studies are needed on ways to maximize peak bone mass in girls and boys. Parents and children alike can benefit from following these suggestions:

• Make sure you get enough calcium and vitamin D throughout your life.
• Exercise regularly, using resistance and high-impact activities.
• Eat a healthy diet and follow a healthy lifestyle.