The goal of the "Got Milk?" campaign may be to sell more milk, but the main beneficiaries of this advertising effort could well be the bones and health of current and future adults.
As we learn more about the benefits of calcium and the particular importance to a healthy skeleton of calcium during childhood and adolescence, nutrition experts are becoming increasingly alarmed about the failure of most young people to drink enough milk.
Although calcium can be obtained from foods other than milk, as well as from supplements, it is the main source of this vital nutrient for young Americans. Few children or adults consume enough cheese and nondairy calcium-rich foods, like collard greens or broccoli, to meet the daily calcium requirements.
Some people avoid milk because they are lactose-intolerant and
experience flatulence or diarrhea when drinking the milk on an empty stomach.
Nutritionists, however, have found that most lactose-intolerant people can handle up to three glasses a day if they are consumed slowly and with meals.
And nearly every supermarket now sells lactose-reduced and lactose-free milk, although usually at twice the price of regular milk.
Children Are Shortchanged
The National Academy of Sciences says that children ages 4 through 8 should be consuming 800 milligrams of calcium daily and that teenagers 13 through 18 need 1,300. People 19 through 50 need 1,000 milligrams of calcium a day, and those 51 and older are urged to consume 1,300 milligrams, the academy says.
According to Dr. Duane Alexander, director of the National Institute of Child Health and Human Development, "Without including milk in the diet, it is nearly impossible to meet calcium needs" through foods alone. Milk, he noted, supplies slightly more than half the dietary calcium consumed by children in this country.
A national survey in the mid-1990's, however, revealed that only 13.5 percent of girls and 36.3 percent of boys ages 12 to 19 consumed the recommended amount of calcium.
Such data, and especially the poor calcium intake among adolescent girls, prompted the institute to begin a public information campaign called "Milk Matters" to educate health professionals, parents and children about the importance of consuming enough calcium, particularly from milk and other dairy products like yogurt and hard cheese, to protect bone health.
Far too many children consume carbonated soft drinks and fruit drinks and juices instead of milk or dairy-based drinks. Schools that permit soda vending machines in or near their cafeterias (in exchange for big bucks from beverage companies) hardly help matters. Yet middle schools and high schools that installed vending machines that dispense flavored as well as plain milk report that they routinely sell out each day, with chocolate milk being the overwhelming favorite.
In this month's American Journal of Clinical Nutrition, researchers from Cincinnati Children's Hospital reported that adult women who consumed less than a glass of milk a day during childhood had flimsier bones and a twofold greater risk of fractures than those who consumed a glass of milk or more each day as they were growing up.
Now, a glass is hardly enough milk to meet the daily recommended intake of calcium for anyone. So it is a safe bet that if the researchers had compared those who drank less than a glass of milk a day with those who drank three or more glasses during childhood, the differences in bone density and fracture risk would have been that much greater.
Dr. Connie Weaver, who heads the department of foods and nutrition at Purdue University, points out that "adolescence is a critical time to optimize bone health" because about half of an adult's skeletal mass is accrued during the teenage years.
For girls, 95 percent of the body's total bone mineral content is accumulated by age 17, and 99 percent is completed by age 27. Thus, a girl who shortchanges herself on calcium will enter adulthood with a skeleton that is less than adequate, and she will face an increased risk of fractures throughout life.
"Current calcium intakes of adolescents are well below recommended levels," Dr. Weaver said. "Studies indicate that four to five servings a day of calcium-rich foods are needed to optimize peak bone mass during adolescence."
An eight-ounce serving of a calcium-rich food like milk or yogurt would provide at least 300 milligrams of calcium. Comparable amounts can be obtained from calcium-fortified soy milk and orange juice and a cup of cooked collard greens. Many breakfast cereals are now fortified with calcium. And even some milks have added calcium.
Unlike most other foods, milk is fortified with vitamin D, which the body needs to absorb calcium through the digestive tract. The natural sugars in milk also aid in calcium absorption -- another reason milk is the preferred dietary source of this bone-building mineral.
Other Health Benefits
Emerging research is showing that the importance of calcium goes well beyond bones.
Studies using supplements have indicated that calcium is good for the heart. Calcium helps to lower blood pressure in about one-third of people with hypertension.
Researchers at the University of Wisconsin showed that hypertensive women who took 1,500 milligrams of calcium a day, in addition to their medication, for four years experienced a significant drop in blood pressure, while those who took just medication experienced an overall rise in blood pressure.
Calcium also improves blood lipid levels. In a study at the University of Auckland in New Zealand, researchers found that a daily 1,000-milligram dose of calcium citrate increased protective H.D.L. cholesterol levels and lowered harmful L.D.L. cholesterol, a change that could reduce the rate of cardiovascular problems by 20 percent to 30 percent.
Although the role of calcium in cancer is still being investigated, the latest study, which followed 135,000 health professionals for 10 to 16 years, found that total calcium intake in excess of 1,250 milligrams a day was associated with a nearly 30 percent lower risk of developing cancer in the lower colon.
There is biological support for this finding. Calcium protects the bowel by binding bile acids and reactive fatty acids, which are known to promote cell growth.
Also, in a colon cancer prevention study, a daily 1,200-milligram calcium supplement resulted in a 20 percent decrease in the recurrence of colorectal adenomas, benign growths that are the precedents to colorectal cancer.
And various studies have suggested that calcium may play a role in countering premenstrual syndrome and polycystic ovary syndrome.