Bone health across the lifespan. (Ages & Stages).

Doctors who specialize in osteoporosis know that, although the disease primarily affects women in their 60s and beyond, its seeds are sown back in childhood. Here's a look at bone growth through the ages--from birth to old age.

Early childhood. The bones of a fetus and newborn are primarily composed of cartilage, the rubbery material of noses and earlobes. During childhood, liquid crystals of calcium within this cartilage solidify through a process called mineralization," kind of like water freezing into ice. (11, 12) For that mineralization to occur and keep occurring throughout childhood, however, it's vitally important that children get enough exercise, calcium and vitamin D, says Laura Tosi, MD, chief of Orthopedic Surgery at Children's National Medical Center in Washington, DC. That isn't easy these days. Outside play, once a staple of childhood, has given way to video games and television. And if kids don't play outside, they often don't get enough sunlight to make adequate vitamin D (especially if, when they are outside, they're slathered in sun lotion), she says.

Also, kids are much more likely to drink soda or juice these days than milk, which remains one of the best sources of calcium and vitamin D in early life (300 mg of calcium in one 8-ounce glass). In fact, variations in the amount of calcium kids get may account for a five to 10 percent difference in adult bone mass and a 50 percent difference in the hip fracture rate later in life. (1)

Puberty. Chalk up that adolescent growth spurt to the fact that the majority of bone is laid down in adolescence. This "speeding up" of bone formation begins around age 11 in girls and 12 or 13 in boys. Unfortunately, this is also the time when girls begin to significantly reduce their calcium intake. In fact, over 80 percent of girls age nine to 19 don't get the recommended average daily amount of calcium. (1) Adolescent girls are also at greater risk for anorexia and other eating disorders than boys, which can play havoc with estrogen levels, leaving some young women with the fragile bones of an 80-year-old by the time they're 20. (1)

Other factors also play a role in adolescent bone formation. Poor activity levels, smoking, even a significant illness that requires prolonged bed rest can interfere with a girl's complete acquisition of bone. (11) And adolescent girls are hardly hitting the playing fields in droves. In 2001, 38 percent of female high school students reported a level of physical activity that did not meet the criteria for the recommended amount of either moderate or vigorous physical activity. (13)

Menopause. Once you enter menopause you can lose up to 20 percent of your bone mass. Here is where the bone you "banked" as a girl becomes so important. But it doesn't mean you're off the hook when it comes to lifestyle. Nutrition, exercise and quitting smoking are still just as important.

Unfortunately, adult women are no more likely to get enough exercise than their children are, with 39 percent of adults reporting in 2000 that they didn't engage in physical activity during leisure time. The older you are, the less likely you are to exercise, with more than half of Americans 75 and older (who were nor institutionalized) saying they got no physical activity during leisure time. Even worse: at nearly all ages, women were less physically active than men. (14)

RECOMMENDED CALCIUM INTAKE *

                        Amount in mgs
Ages                    (Milligrams)

Birth to 6 months        210 mg daily
6 months to 1 year       270 mg daily
1 to 3 years             500 mg daily
4 to 8 years             800 mg daily
9 to 18 years           1,300 mg daily
19 to 50 years          1,000 mg daily
51 and older years      1,200 mg daily
Pregnant & Lactating *  1,000 mg daily
* 14 to 18 years        1,300 mg daily

Sources: National Osteoporosis Foundation, National Academy of Sciences

RECOMMENDED VITAMIN D INTAKE

                          Amount in IUs
Ages                  (International Units)

Early childhood
for healthy children      200 IU daily
Adolescents               200 IU daily
Adults, up to aye 50      200 IU daily
Adults, ayes 51-70        400 IU daily
Adults, ages 70
and older                 600 IU daily

Sources: U.S. Centers for Disease Control and Prevention, National
Academy of Sciences

References

(1.) NIH Consensus Statement: Osteoporosis Prevention, Diagnosis and Therapy. March 27-29, 2000.

(2.) Women's Complete Health Book, American Women's Medical Association, the Philip Leif Group, 1995

(3.) Feskanich D, Willett W. Colditz G. Walking and leisure-time activity and risk of hip fracture in postmenopausal women. JAMA. 2002 Nov 13;288(18):2300-6.

(4.) Turner LW, Bass MA, Ting L, Brown B. Influence of yard work and weight training on bone mineral density among older U.S. women. J Women Aging. 2002;14(3-4):139-48.

(5.) Osteoporosis: Progress and Prevention. National Institutes of Health. 2000. www.niams.nih.gov

(6.) Screening for Osteoporosis in Postmenopausal Women, ACHQ, September2002, http://www.ahrq.gov

(7.) Once is Enough: A Guide to Preventing Future Fractures, Notional Institutes of Health, revised January 2003. www.osteo.org

(8.) Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results From the Women's Health Initiative randomized controlled trial. JAMA. 2002 Jul 17;288(3):321-33.

(9.) FDA Approves New Labels for Estrogen and Estrogen with Progestin Therapies for Postmenopausal Women Following Review of Women's Health Initiative Data. FDA Talk Paper. Jan. 8, 2003.

(10.) Medications to Prevent and Treat Osteoporosis, National Osteoporosis Foundation fact sheet, www.nof.org

(11.) Kids and their bones. National Institutes of Health. www.niams.nih.gov

(12.) Sanghavi, Darshak. A Map of the Child: A Pediatrician's Tour of the Body. Henry Hold, 2003.

(13.) Calcium Crisis, The Ups & Downs of Adolescence, June 2000. www.ianr.unl.edu

(14.) COC Fact Book, 2002.

(15.) Dietary Reference In takes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride ore available from the National Academy Press, August 1997.