To the 14 middle-school girls, spending three weeks of their summer vacation in a college sorority house with free food, interesting classes and tons of recreation was a great adventure.
Yet there were drawbacks: They all had to eat the exact same food including snacks. They had to give 28 different samples of blood and collect all of their bodily wastes. Most important, they had to drink all their milk and eat all their yogurt and ice cream, to the extent of rinsing out the cartons with deionized water which they then had to drink.
These were the guidelines at Camp Calcium, sponsored by Purdue Uni- versity in West Lafayette, Ind. The rinsing was a particularly important rule since the purpose of this camp in reality a nutrition-research pro- ject, was to measure calcium retention.
In the end, the campers, aged 12 to 14–along with 11 women ranging from 19 to 32 years–provided convincing evidence that girls at the peak of their skeletal development cycle put about five times more calcium to use for their bones than women even a few years older.
The experiment, part of an ongoing multi-year calcium research project conduceed by Conrlie Weaver, director of Purdue’s department of food and nutrition, goes a long way toward proving that the best way to guard against the ravages of osteoporosis is to eat enough calcium when you are young.
Osteoporosis, a disease that results from deteriorating bones, usually occurs in old age as the body leaches skeletal calcium to provide for other bodily needs. It’s a growing, cross-cultural disease that affects women in particular and costs $10 billion a year in fractures, hospitalizations, incapacitation and death.
“Much previous work has concentrated on preventing bone loss,” Weaver says. “So we theorized the opposite way: What if you build extra bone when you are young so that you can afford to lose some of it when you grow old?”
The Camp Calcium study shows that early adolescence, when calcium retention seems to be highest, is the best time to build bone. In other words, a 12-year-old girl can make a valuable choice about the quality of her old age, Weaver says.
Although calcium works the same in men as women, adolescent boys tend to consume more calcium if only because they consume more calories. On the other hand, girls, in an eternal quest to be thinner, are more likely to drink a can of diet soda than a glass of milk, says Weaver.
Her experiment reinforces some earlier findings that very little of the calcium a woman eats after she reaches her early 20s is added to bone tissue. No study participants older than 21 showed any calcium retention.
That doesn’t mean calcium is not a valuable component of the diet after age 21, Weaver says. On the contrary women in particular need as much as they can get for body maintenance and to retard bone loss. It’s just that they won’t be storing it.
The study held in Purdue’s Delta Gamma sorority house really functioned as a camp, Weaver says. Several of the women participants also served as counselors. Girls attended classes in nutrition, science and fitness plus activities that included swimming, canoeing, horseback riding and museum-going. During the evenings they ate pizza, practiced hairdressing and makeup and, well bonded, Weaver says.
“We had to watch them every minute,” Weaver says. “We literally supplied them with everything they put in their mouth. Everybody ate precisely the same thing in exactly the same proportions. They had to consume every bit of it. There could be no skimpy eaters
“They couldn’t stop at a drinking fountain without supervision.”
Each meal was weighed and measured to adjust individual calcium consumption to exactly 1,332 milligrams a day –the equivalent of about 4 glasses of milk and about the recommended daily allowance for girls and young women.
Because researchers knew how much calcium was consumed, they could calculate from blood tests and waste analyses how much the skeleton absorbed. Results showed that calcium retention for adolescents was 326 milligrams per day compared with only 73 milligrams for the women, on average.
“The results show that even during the most rapid growth period though, the most efficient you can be is 25 percent retention,” Weaver says. “That’s if you consume the equivalent of four glasses of milk a day
“We know there are a lot of kids in this country that get two or less. They aren’t going to build as much bone.”
Weaver is working on a similar study to determine “specific pre- scriptions” of calcium so that adolescents can get the maximum absorption.
Osteoporosis, she tells the Camp Calcium girls–or any girls–is completely preventable if you act when you are young.
“Picture what you want to look like in 70 years,” Weaver says. “Do you want to be jogging or in a wheel chair?”
