A WALK DOWN the beverage aisle of any supermarket tells a sad tale about the future of American bones.
The shelves are stacked with canned, bottled and packaged fruit drinks and juices, flavored soda, mineral and plain waters and packets of artificial drink mixes. The frozen food bins hold more ,, of the same. The dairy counter pales by comparison.
And the young people who are the primary consumers of calcium-poor non-dairy beverages may be on their way to building inadequate bones.
Even toddlers these days may not be getting enough bone-building calcium because many mothers, worried about allergies and mucus formation in response to milk, fill their babies' bottles and cups with apple juice instead of calcium-rich milk.
Two recent studies indicate that large numbers of healthy youngsters are not consuming enough calcium to reach a peak bone mass large enough to protect them from fractures in their youth, let alone in their adult years, when bones inevitably deteriorate.
This prospect, combined with ever-increasing life expectancy, portends an epidemic of osteoporosis decades from now that will be far worse than what exists today.
From birth onward, the density and size of bones usually increase as children grow. In most people, bone mass reaches its maximum by about the age of 35. At that point nearly everyone begins to lose bone, gradually at first and then, in women, at an accelerated rate as they go through menopause.
The result for millions of older Americans is osteoporosis, the weakening of bones with age as calcium and other minerals are lost faster than they can be replaced.
Osteoporosis currently affects an estimated 20 million Americans. Many of them will eventually become incapacitated; some will even die of medical complications that ensue when, for example, their hip or leg bones break.
While most of the concern about osteoporosis has focused on women, who are the primary victims, men too lose bone with age. But men do not live as long as women do and, since men start out with more bone tissue, it usually takes longer before they suffer the consequences of bone loss.
Bone researchers believe that a main defense against osteoporosis is to start out with as much bone as possible. Their calculations suggest that a 5 percent increase in peak bone density among young adults could mean a 50 percent reduction in the risk of fractures in their older years.
No one questions the crucial role calcium plays in building strong bones in children.
Calcium from foods is absorbed through the digestive tract with the aid of activated vitamin D, a hormone the body makes from the vitamin D in foods and the vitamin D that is made in skin after exposure to sunlight.
To help assure that people get enough vitamin D even in winter months when sun and time outdoors are limited, commercially processed milk has long been fortified with this vital nutrient.
But consuming the needed nutrients is only part of the story. Bones, like muscles, do not maintain themselves if there is no tension on them. That is why people who are bedridden and astronauts flying beyond the tug of gravity lose bone mass rapidly no matter how much calcium they consume.
Regular physical exercise is a crucial factor in building and maintaining strong bones.
If young members of the soft-drink generation also spend too many hours in front of a television set instead of participating in energetic activity, they place themselves at double jeopardy of poor bone development.
Trouble starts early. In a study of 164 healthy children from 2 to 16 years old, Dr. Gary M. Chan, a pediatrician at the University of zTC Utah Medical Center, discovered that those who consumed more than 1,000 milligrams of calcium a day had denser bones in their arms than those who ingested less calcium.
Chan expressed special concern about adolescent girls, the weight-conscious consumers of diet soda, whose calcium intake was often far below the 1,200 milligrams a day recommended for 11-to-24-year-olds.
Since approximately 45 percent of an adult's skeleton is built and enlarged during adolescence, being shortchanged on calcium at this stage of life is especially damaging.
Another recent study at Ohio State University found a direct relationship between current calcium intake and the density of spinal bones in 49 healthy adolescent girls.
Whereas 67 percent of the 8-to-10-year-old girls consumed the recommended 800 milligrams of calcium daily, only 16 percent of those 11 to 18 fulfilled the 1,200 milligrams recommended for their age group.
The researchers urged girls to consume more calcium if they want to reduce the risk of spinal deterioration after menopause, which can lead to a loss of height and the bent posture known as dowager's hump.
The problem of calcium nutrition worsens after adolescence. Dr. John J.B. Anderson, a professor of nutrition at the University of North Carolina School of Public Health, has been monitoring the calcium intake and bone density of college-age women.
In studies of about 800 college women 18 to 22 years old, he has found that about three-fourths of students, all of whom can afford to eat properly, do not consume nearly enough calcium.
Anderson said he also found an even stronger relationship between physical activity and bone mass.
"If girls could be more active, maybe their bones would fare better with less calcium, since activity stimulates bone growth," he said. "Drinking pop while sitting in front of the TV is undermining the future skeletal health of America."