Camp Calcium
Today’s Dietitian
By Jaime Ruud, MS, RD, and Jennifer Meyer, RD
Vol. 6, No. 11, p. 41

Teenaged boys and girls attend this camp for the calcium, but crafts and climbing trees make it summer camp the way you remember it.

When you think of summer camp, you may envision sitting by the campfire singing songs and eating S’mores. But Purdue University’s Camp Calcium isn’t your typical summer camp. This summer, 43 adolescent boys and girls had the unique opportunity to take part in a controlled diet study examining the role of calcium and dairy products in the body’s regulation of fat.

Connie M. Weaver, PhD, distinguished professor and head of Purdue’s food and nutrition department, and her colleagues have been studying calcium metabolism throughout the life cycle, particularly during periods of high demand such as adolescence. The summer camp began in 1990 and is funded by a National Institutes of Health grant, which will continue through 2007 as a result of competing renewals.

Camp Calcium participants spent two separate three-week sessions on the Purdue campus where they lived in a student residence hall and ate all their meals together. Each day, subjects were fed a controlled diet of three meals, two snacks, and beverages with a prescribed amount of calcium and other nutrients. All subjects consumed a controlled diet during one session providing 650 milligrams of calcium per day, including dairy foods, which closely resembles the daily calcium intake of an average teenager.

During the other session, subjects received the control diet plus calcium from calcium carbonate or received the control diet plus calcium from additional dairy, which doubled the amount of calcium compared with the control session, or 1,300 milligrams per day, the amount currently recommended for adolescents. The diets are designed to aid researchers in determining whether calcium alone or in the form of dairy foods plays a role in managing body weight through the body’s ability to burn or absorb fat.

When campers are not participating in testing, there are various activities they can be involved in that more closely resemble a typical summer camp environment. These activities include attending educational programs on Purdue’s campus, recreational activities such as climbing trees or playing soccer, or crafts, games, skits, and karaoke.

Weaver and her colleagues have chosen to focus on adolescents because they believe lifestyle factors that control body fat and weight may have a bigger payoff in children than adults. According to Weaver, “During the pubertal growth spurt, there may be more opportunity to influence body fat gains by diet than during other life stages.” She hopes to identify potential mechanisms responsible for the effect of calcium on fat absorption and oxidation, which might lead to body fat management and regulation of body weight.

Recent studies suggest that calcium, and particularly dairy products, may help people lose weight.1,2,3,4 Yet, according to Weaver, few studies have provided the level of dietary supervision the kids at Camp Calcium will receive.

“What sets Camp Calcium apart from others studies is the fact that our research is among the first to investigate humans using a control diet,” Weaver says. Other studies have either assessed calcium intake by questionnaires or records or have given subjects diet prescriptions. “These approaches are less accurate indicators than actual calcium or dairy product intakes,” she says. “The disadvantage of our study compared to other studies is that it’s not long enough to have changes in body fat and weight as an outcome measure. We have to be satisfied with mechanisms.”

Weaver is not the only researcher interested in the mechanisms linking calcium and weight loss. In a 2004 study published in Obesity Research, Michael B. Zemel, PhD, professor of nutrition at the University of Tennessee and author of The Calcium Key: The Revolutionary Diet Discovery That Will Help You Lose Weight Faster (Wiley, 2004), and his colleagues found that obese adults on a calorie-restricted diet who consumed more calcium, particularly calcium from dairy foods, lost more weight and fat than those restricting calories alone.1

In his study, 32 obese young adults were randomly assigned to one of three groups: low calcium (400 to 500 milligrams per day) and dairy products; high calcium from supplements (1,200 to 1,300 milligrams per day) but low in dairy products; and high dairy (three servings of milk, cheese, or yogurt daily for a total of 1,200 to 1,300 milligrams of calcium per day). All participants consumed a diet that was 500 calories lower than their daily calorie requirement to induce weight loss of roughly 1 pound per week.

After 24 weeks, those on the high-dairy diet lost the greatest percentage of total body weight (11%)—significantly more than those in the high-calcium supplemented group (9%) and the low-calcium/low-dairy group (6%). Fat loss was significantly augmented by the high-calcium and high-dairy diets by 38% and 64%, respectively, compared with the standard diet. The researchers were surprised but pleased to find that compared with the control diet, the high-calcium, but particularly the high-dairy diets, augmented fat loss specifically from the trunk area of the body (19%, 50%, and 66% of total fat loss, respectively).

In addition, the high-dairy group showed significant improvement in glucose tolerance after six months on the diet, while the other two groups showed no change. The high-dairy diet produced a significant decrease (44%) in plasma insulin levels as well as a “modest reduction” in systolic blood pressure; the other two groups did not.

The authors say dairy foods may exert a significantly greater antiobesity effect than calcium alone due to a synergistic or independent effect of bioactive components such as the angiotensin-converting enzyme (ACE) inhibitory activity of milk proteins or other bioactive components in whey. Milk proteins, both casein and whey proteins, are a rich source of ACE inhibitory peptides, and studies in hypertensive animals show that these peptides can significantly reduce blood pressure.5

Another recent study found that adolescent girls who consumed the most dairy foods weighed less and had less abdominal fat than those who consumed fewer dairy foods.6 Rachel Novotny, PhD, RD, professor and chair of the department of human nutrition, food, and animal sciences at the University of Hawaii at Manoa in Honolulu, and her colleagues studied 323 girls aged 9 to 14. They collected three days of dietary intake, supplement intake, physical activity, and anthropometric measurements (height, weight, and iliac skinfold thicknesses), along with clinical tanner stage of maturation and ethnicity. Mean total calcium intake was 736 milligrams per day. Calcium intake, age, and physical activity were significantly negatively associated with iliac skinfold thickness, whereas height, tanner breast stage, and ethnicity were positively associated. In short, the girls who consumed more calcium had less body fat than the girls who consumed less calcium.

“Our study found that adolescent girls who ate an additional serving of dairy had significantly lower body fat when age, ethnicity, growth stage, activity level, and calorie intake were the same,” says Novotny. “Just one serving of milk was associated with 0.78 millimeter lower iliac skinfold thickness.”

All these studies come at a time when obesity rates are soaring. An estimated 16% of children and adolescents aged 6 to 19 are currently overweight (>95th percentile).7 There are twice as many overweight children and almost three times as many overweight adolescents today as there were in 1980, and there is little indication that the prevalence of overweight among children is decreasing.7

Novotny believes her findings might provide further evidence that higher calcium intake may play an important role in reducing the growing problem of obesity in the United States, especially among children.

“Knowing the trends of decreasing dairy consumption and increasing soda consumption, and putting together the kind of research being done, there is something important here in terms of weight management,” Novotny says. “It would be smart to encourage all people, especially young people, to eat the recommended amount of dairy foods.”

Rebecca Reeves, DrPh, RD, FADA, American Dietetic Association (ADA) president-elect and founder of the ADA Weight Management Dietetic Practice Group, agrees. “There is preliminary evidence that suggests that including three servings of dairy foods daily into eating plans for weight management may increase the amount of weight loss and improve the body’s ability to mobilize and burn fat,” says Reeves. “Encouraging clients to consume more nonfat and low-fat dairy products just makes good sense since most young adults do not eat adequate amounts of calcium on a daily basis.”

While dairy products may play a role in weight loss, we still have to control for calories, Novotny says. “In other words, we have to substitute something for something else. For example, substituting milk for soda is a really good idea.”

In addition to the reports about dairy’s role in weight management, there are many other reasons to encourage consumption of calcium-rich foods like milk, cheese, and yogurt. Calcium’s role in reducing the risk for osteoporosis and delaying or minimizing age-related bone loss has been well-established.8 The Dietary Approaches to Stop Hypertension (DASH) study found that a low-fat diet including three servings of dairy products and eight to 10 servings of fruits and vegetables significantly lowered blood pressure.9 The DASH researchers estimated that if all Americans adopted the DASH diet, there would be a populationwide reduction in blood pressure, reducing coronary heart disease by 15% and stroke by approximately 27%. There is also evidence that links intake of dairy foods with reduced risk of some cancers,10 kidney stones,11 and dental caries.12

A report published in the American Journal of Hypertension projected that if Americans increased their dairy intake to three to four servings each day, there would be a savings of $200 billion in healthcare cost’s over five years or $26 billion in the first year alone.13 In reviewing approximately 100 studies spanning two decades, the authors found strong scientific evidence that dairy foods could play a role in reducing the risk of nine common diseases or conditions, including obesity, hypertension, type 2 diabetes, coronary artery disease, stroke, kidney stones, osteoporosis, colorectal cancer, and pregnancy-related complications.

— Jaime Ruud, MS, RD, is a research technologist for the department of nutrition and health sciences at the University of Nebraska. She is also co-owner of Nutrition Link Consulting, a private practice in Lincoln, Neb., that specializes in freelance writing and nutrition analysis.

— Jennifer Meyer, RD, is program director of nutrition education for the Dairy Council of Nebraska, Inc., Omaha.

References for this article are available upon request by e-mailing TDeditor@gvpub.com.

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