Osteoporosis: Prevention in Teen Years (cont.)
Growing bone is especially sensitive to the impact of weight and pull of muscle during exercise, and responds by building stronger, denser bones. That's why it's especially important when you're growing a lot to be physically active on a regular basis. And as far as bone is concerned, Calvo says impact activity like jumping up and down appears to be the best. "But the important thing is to get off the couch and get moving at some activity. It really is a matter of 'Use it now, or lose it later'." Such activities include sports and exercise, including football, basketball, baseball, jogging, dancing, jumping rope, inline skating, skateboarding, bicycling, ballet, hiking, skiing, karate, swimming, rowing a canoe, bowling, and weight-training. And when your parents make you mow the lawn, rake leaves, or wash and wax the car, they're doing your muscles and bones a favor. FDA's Welch adds, "Day-to-day activities that start in the teen years, like walking the dog or using stairs instead of elevators, can become life-long habits for healthy bones."
Avoid Bone Risks
Some habits in the teenage years can steal calcium from your bones or increase the need for it, weakening the skeleton for life. Skipping meals is risky for bone, Welch says. In our three-meal-a-day society, skipping a meal may reduce by a third your chance of getting your 120%DV for calcium -- simply by eliminating one occasion to eat. Replacing milk with nondairy drinks like soda pop or fruit-flavored teas or drinks is another eating habit that prevents bones from getting the calcium and other nutrients they need.
In a survey comparing 1994 daily beverage intakes with those in the late 1970s, the U.S. Department of Agriculture found a switch from milk to other drinks among young people:
Alcohol abuse and cigarette smoking can hurt bone. Calvo says, "Alcohol abuse can cause loss of calcium, magnesium and zinc in the urine. Many who abuse alcohol also have poor diets and malnourished, weaker bones." Cigarette smoke is also toxic to bone and can influence how much exercise you get because it affects your stamina, she says. Eating disorders can weaken bone. The repeated vomiting in bulimia and extreme dieting in the appetite disorder anorexia can upset the body's balance of calcium and important hormones like bone-protective estrogen, decreasing bone density. And extreme exercising by young women with or without eating disorders can postpone or stop menstruation, when blood levels of estrogen are reduced.
Small Changes for Big Benefits
As a disorder of aging, osteoporosis may seem far away for worry when you're 15. But, small changes today for better bones tomorrow may be more important than you might guess. Laura Bacharach, M.D., of Stanford University, wrote in Nutrition & the M.D. last year that adolescents who make "even a 5 percent gain in bone mass can reduce the risk of osteoporosis by 40 percent." And this is in addition to "immediate benefits of feeling stronger and more fit now with these changes!"
"Calcium! Do You Get It?"
Unlike boys, growing girls typically have low calcium intakes. Concerned about the low intakes, the Food and Drug Administration recently developed a pilot education program, funded by the agency's Office of Women's Health, just for girls ages 11 to 14. "Calcium! Do You Get It?" encourages girls to get enough calcium and exercise for healthy bones and to carry these healthy behaviors throughout life. This article includes much of the information in the program.
Girls Don't Get Enough Calcium
Between the ages 11 and 24, people need at least 1,200 milligrams (mg) of calcium every day. A 1995 survey by the U.S. Department of Agriculture, however, found that girls and young women 12 to 19 got only 777 mg of the mineral daily, overall. Intake by boys and young men in the same age group was 1,176 mg daily. Daily calcium intake by preteen girls was far short of the recommended level also in 1990-1992 and fell with age, wrote Ann Albertson, M.S., R.D., and others recently in the Journal of Adolescent Health. Calcium consumption was only 781 mg at ages 11 to 12, 751 at ages 13 to 14, and a mere 602 mg -- barely half what it should be -- at ages 15 to 18.
Why Is Calcium Intake in Girls and Young Women So Low?
USDA's Agricultural Economic Report No. 746 gives some clues. Compared with other children, female adolescents:
Eat Enough Calcium -- and a Balanced Diet, Too
To get enough calcium for growing bones, each day you need to eat foods whose %Daily Value for calcium adds up to 120 percent. Because the amount of calcium in foods can vary, read the food label check the %DV for calcium in what you eat. So your body will have all the other nutrients it needs, too, be sure to eat the recommended number of servings from the food groups that make up the Food Guide Pyramid:
As shown in the table below, each group includes foods that provide calcium. The food examples are listed by their serving size and %DV for calcium.