Dairy products have long been recognized as nutrient-dense foods due to their high-calcium content and bioavailability, high levels of other essential nutrients and relatively low cost. Getting adequate amounts of calcium and other nutrients from dairy has also been demonstrated to help reduce the risk of high blood pressure and colon cancer. Other potential benefits of calcium that have been reported include lowering the risk for kidney stones and premenstrual syndrome. And most recently, evidence is mounting that diets high in calcium and, in particular, from calcium-rich dairy foods, are effective in enhancing body weight and body fat loss in calorie-restricted diets.
The recognition by nutrition experts of calcium's critical role in bone health contributed substantially to the Institute of Medicine of the National Academy of Sciences' decision in 1997 to increase calcium intake recommendations for adolescents, adults and adults more than 51 years of age. Unfortunately, national nutrition surveys show that few Americans are meeting the dietary recommendations for calcium intake.
While it is difficult to accurately estimate inadequate intake of calcium, currently, only about 32% of boys and 12% of girls aged 12 to 19 years consume the recommended amounts of calcium. In adult men and women 20 years and over, only 27% and 10.2%, respectively, meet recommended amounts of calcium. In the elderly 70 years and over, only 13% of men and 4% of women meet recommended calcium intakes. Clearly, Americans' low calcium intake is recognized as a major public health problem and is identified as one of the priority nutrition problems in the United States.
Health professional organizations agree that conventional foods are the preferred source of calcium and that low-fat dairy products are the best sources of calcium. This is because not only are they rich in calcium, they also contain essential nutrients including protein, phosphorus, potassium, riboflavin, magnesium, zinc, and vitamins A, B12 and D, which are all necessary for optimal bone health and human growth and development. To help children, adolescents and adults meet their calcium needs, government education programs and health professional organizations including the American Heart Association, the American Academy of Pediatrics, the National Medical Association and Health Canada encourage up to four servings of milk throughout the day.
Milk matters more
The Dietary Guidelines for Americans-2000 recommends that Americans two years and older consume two to three dairy servings per day depending on age, with each serving supplying 300mg calcium. These recommendations are based on idealized diets that were developed for the Food Guide Pyramid (FGP) using recommended dietary patterns that include significant amounts of non-dairy calcium (250-475mg per day) derived from recommended intakes of vegetables, whole and enriched grains, fruits and meat. However, most Americans consume substantially less than the recommended servings of whole and enriched grains, dark-green leafy vegetables, legumes and fruit. For example, the FGP recommendations of four servings of dark-green leafy and deep yellow vegetables and legumes per day for a 2,200 calorie diet is three to four times higher than current consumption by Americans two through 70 years of age and six to 8 1⁄2 times higher than current consumption by children two to 19 years old.
The suggested amounts of whole grains recommended for a 2,200 and 2,800 calorie diet are, on average, five times higher than what Americans currently consume. Thus, while intake of vegetables, whole grains and fruits should be encouraged, it is highly unlikely, based on current trends in vegetable and grain consumption, that Americans will get the amount of calcium from these sources as suggested by the FGP. The result: Recommended diets may end up exacerbating low calcium intake by promoting the intake of foods that are generally poor sources of calcium and that have a low probability of consumption, while limiting the intake of excellent sources like low-fat dairy products, which have a substantially greater probability of consumption.
Researching needed servings
Given the low consumption of whole grains, vegetables and fruit by Americans, it is unclear whether the actual calcium intake in persons who consume the FGP recommended two to three servings of dairy are meeting the recommended Adequate Intake (AI) of calcium established by the Institute of Medicine. Researchers have recently evaluated the "actual" consumption of calcium from non-dairy and dairy food sources using the Continuing Survey of Food Intake by Individuals (CSFII) and the National Health and Examination Survey (NHANES), two very large nationally representative dietary surveys that monitor the food and nutrient intakes of U.S. children, adolescents and adult men and women. Their find-ings were highly consistent between both surveys. The chart to the right shows the ideal number of dairy servings required to meet the AI for calcium for each age group.
These results indicate that the number of dairy servings recommended by the FGP should be increased by one serving for all age groups nine years old and greater in order to reduce the likelihood of inadequate intakes of calcium. These results also raise some important considerations for dietary recommendations. It is clear that the FGP recommends idealized diets and thus, if certain foods in the diet are not consumed as suggested, then the intake of certain nutrients may be low. For example, the Dietary Guidelines for Americans-2000 suggests that certain non-dairy sources (e.g., canned fish with bones, fortified orange juice, fortified soy beverage, tofu and some dark-green leafy vegetables) could be consumed to increase calcium in the diet. In CSFII, however, less than 0.2% of the foods consumed by Americans were derived from these items as compared to 10% for milk, cheese and yogurt. These data looked at actual food consumption and suggests that adding one additional serving of dairy products might be more effective for meeting calcium needs than trying to increase non-dairy foods sources. The critical need of dairy products to meet calcium needs is underscored in Healthy People 2010: Objectives for Improving Health. It states: With current food selection practices, use of dairy products may constitute the difference between getting enough calcium in one's diet or not.
Beyond bones
A growing body of literature also exists indicating that consumption of three to four servings of dairy foods per day may help to lower the risk of chronic disease conditions, many of which are costly as well as responsible for considerable morbidity and mortality.For example, a considerable body of scientific evidence exists showing the beneficial effects of dairy food consumption on reducing blood pressure. The results of clinical studies suggest that the consumption of recommended levels of dairy products can contribute to lower blood pressure in individuals with normal and elevated blood pressure. The blood pressure-lowering effect of dairy products is best exemplified by the Dietary Approaches to Stop Hypertension (DASH) clinical trials. These studies demonstrated that a low-fat dietary pattern high in fruits and vegetables and dairy products produced greater reductions in systolic blood pressure and diastolic blood pressure than either a diet high in only fruits and vegetables or a control diet low in both dairy and fruits and vegetables.
Also, rapidly emerging research provides consistent support for a beneficial effect of increased dairy foods on body weight and fat loss. Recent clinical studies have demonstrated enhanced body weight/body fat loss can be achieved when adequate calcium is provided from calcium supplements but is further enhanced by dairy foods, indicating that additional nutrients from dairy foods are playing an important role. In all of these clinical studies the dietary (dairy) calcium intake was equivalent to three to four servings of dairy products (milk, cheese and yogurt) per day as part of a reduced-calorie diet.
In summary, recommending three to four servings from the milk group for all individuals greater than nine years old is reasonable, practical and necessary in order to ensure adequate intakes of calcium. Furthermore, according to a new study that estimated healthcare savings associated with adequate dairy foods intake, it is reasonable to expect long-term public health benefits and potential healthcare cost savings from recommendations to increase the consumption of dairy foods by helping Americans meet their calcium needs, as well as increasing intake of other synergistic nutrients associated with dairy foods, including potassium, magnesium, phosphorus, and vitamins D, A, B12, riboflavin and niacin.
