Calcium is a mineral that plays a critical role in the proper functioning of blood vessels, muscles, nerves and glands as well as providing skeletal bone strength throughout life. Ninety-nine percent (99%) of calcium is contained in bones and the remainder is in blood and tissue fluids. Since Bone Density doesn't reach its peak until the decade between 20 and 30 years, adequate calcium intake during the teen and early adult years is critical to support the continued production of well mineralized bones with adequate calcium stores.

[D]uring the transition from middle adolescence to young adulthood, there was a decrease ... in the average daily intake of calcium and dairy products ...

Unfortunately, a US national survey showed that only half of males and one-fifth of females between the ages of 19-30 get the recommended amount of calcium. In fact, between ages 20-29, 39% of men and 43% of women ate one serving or less of dairy products daily.

In order to develop effective educational, medical, and behavioral interventions to improve these habits, researchers looked at what it is that prevents young adults from taking in enough calcium. Their findings were published in the July issue of Nutrition Education and Behavior.

The researchers began the study with a group of 1541 young adults (45% male; 55% female) with an average age of 15.9 years. They gave the subjects questionnaires to complete in their classrooms. Five years later in 2003-2004, the same group of students were sent a second questionnaire in the mail. Of the original group, 68% completed both parts.

Researchers explored personal, behavioral, and environmental factors that had the potential to influence dietary intake of dairy products and other calcium-rich foods. For example, they asked about participants' knowledge about the benefits of healthful eating, and whether they were able to achieve healthful eating themselves. They asked about their taste preferences for milk and dairy and about their feelings about their weight and body image. They also inquired about lactose intolerance, an inability to digest milk products without unpleasant gastrointestinal symptoms.

They also focused on behaviors which might impact eating habits including how often the respondents ate breakfast, lunch and dinner, how often they ate fast food, whether they helped with food preparation and shopping, whether they were athletic, and how often they watched TV.

They also explored family life and home environments which can impact diet by asking whether their parents or peers cared about or encouraged healthful eating, how often the family ate together, and whether the family could afford sufficient food.

When the second survey was conducted, respondents, who were now past high school age, were asked what they had done after high school, and whether they were living independently, with their parents, or on campus.

At both times participants answered a diet questionnaire including 18 foods and beverages that contained milk or other dairy products to assess changes in calcium, dairy, soft drink, and caloric intake. The food questionnaires revealed that during the transition from middle adolescence to young adulthood, there was a decrease for most respondents in the average daily intake of calcium and dairy products both in the amount of calcium-containing foods they ate, and in the amount of calcium in the foods which they chose.

During middle adolescence, more than 72% females and 55% males had calcium intakes that were lower than the recommended 1300 mg daily amount. During young adulthood 68% females and 53% males had calcium intakes lower than recommended allowance for their age, 1000 mg daily. From the first study to the follow up, both males and females reduced their milk intake. Only 38% of females and 39% males increased their calcium intake over the five years. Most females reduced their calcium intake by average of 153 mg and males by 194 mg daily.

Among the study's findings:
  • Having milk available at mealtimes increased the calcium intake in both males and females.
  • Among females, concern about health and feeling personally competent to make healthful choices, were associated with both higher calcium intake at follow up and increases in intake over time.
  • Participants who watched more television were more likely to have more reduced calcium intake at follow-up.
  • Liking the taste of milk and eating together as a family were both associated with higher calcium intake.
The study also uncovered a number of perceived barriers to healthful eating (such as, it's too expensive, I don't know what to buy, my parents do the shopping and I don't have any choice, I don't have time to sit down and eat healthy food). These were, of course, associated with lower calcium intake; as were the degree to which a person snacked, ate fast food, and drank soft drinks.

Males, with higher calcium intake at follow-up tended to engage in healthful weight control behavior, ate breakfast, had peer support for eating a healthy diet, and were concerned about health.

Factors which did not appear to influence calcium intake included: what the respondents thought the benefits of healthful eating were, their satisfaction with their body, the frequency of eating lunch or dinner, or their involvement with food preparation. Similarly, sports participation, the use of unhealthful weight control behaviors, parental support for healthful eating, and home availability of soft drinks were not shown to be related to calcium intake by either males or females.

The researchers concluded that a decrease in daily intake of calcium, dairy and milk occurs as adolescents transitioned to young adulthood, leaving a majority taking in less than the recommended daily amount. Strategies ranging from making milk available at every mealtime to creating developmentally and culturally appropriate educational interventions to make young adults aware that they may well be taking in too little calcium are necessary to combat this problem with has potential life-long repercussions.

Parents, teens and young adults would benefit from education about the amount of calcium that is contained in various dairy and non -dairy foods as well as the daily intake recommendations, and the importance of continuing to build up calcium stores through the 20s. Good food choices must be modeled at home during family meals, while the teens are still subject to some parental influence and guidance. Colleges could take a role in supporting good nutritional practices in campus dining halls and physicians should take dietary histories during medical visits, and have nutritional information available for their teen and young adult patients.

More information about the calcium content of dairy and non-dairy foods can be obtained: