DAIRY’S ROLE IN CHILDREN’S HEALTH & WELLNESS
Volume 76, Number 5 Sep/Oct 2005
Dairy Products' Role in Children's Health and Wellness
Nutrient Intake. Milk, cheese, and yogurt are naturally nutrient-dense foods providing a high concentration of essential nutrients such as calcium, vitamin D (if fortified), riboflavin, phosphorus, protein, potassium, vitamin A, vitamin B12, and niacin, in relation to their energy value (2,4,22,23). Studies in children and adolescents demonstrate that consumption of dairy products such as unflavored and flavored milk increases calcium intake and improves the overall nutritional quality of their diets (4,24-28). Moreover, intake of dairy foods has been shown to increase the nutritional quality of the diets of children and adolescents without adverse effects on body weight/fat (29-32).
When school-aged children included milk as part of their noon meal, intakes of calcium, vitamins A and E, and zinc increased (24). Intake of flavored milk positively affects children’s calcium intake and overall diet quality (25,26). An investigation of the dietary intake of more than 3,000 children ages 6 to 17 years found that those who consumed more flavored dairy products such as flavored milk and yogurt were more likely to get at least 2 to 3 servings of dairy foods a day and consume more calcium, less added sugar, and lower amounts of saturated fat overall than children who drank more than 16 to 25 ounces of sodas and sweetened fruit drinks every day (26).
As children increase in age, they tend to decrease their milk consumption and increase their intake of less nutritious beverages such as carbonated soft drinks and fruit drinks (5,27,28,33-35). This trend is of concern, especially in light of the substantial proportion of U.S. children with suboptimal calcium intakes and/or who are overweight (5,25,36,37).
Based on data from the Bogalusa Heart Study, the quality of children’s diets decreases from childhood to young adulthood (35). When researchers examined food group consumption patterns and dietary intake from childhood (10 years of age) to young adulthood (19 to 28 years), they found that, despite an increase in total food consumption, intake of low-quality foods (e.g., fats/oils, candy, sweetened beverages, salty snacks) increased twofold, whereas intake of nutrient-dense foods (e.g., dairy, fruits, vegetables, breads/grains, meats) decreased by 10% (35). At age 10, only 50% of children consumed a food from each of the five nutrient-dense food groups and this decreased to only 19% by young adulthood (35).
When researchers surveyed parents of 645 children ages 1 to 5 years regarding their children’s food and beverage intakes, they found that dairy food intake improved children’s diet quality and that children with higher intakes of milk and calcium were less likely to consume nutrient-void beverages (38). According to an analysis of data collected among 1,548 ten-year old children enrolled in the Bogalusa Heart Study and followed for 21 years, milk consumption was significantly lower in those who consumed medium to high amounts of sweetened beverages compared to those with lower or no intake of sweetened beverages (39). Based on these findings, the researchers concluded, "Consumption of milk should be encouraged, particularly if increased soft drink consumption
begins to replace milk consumption” (39).
Bone Health. Optimizing peak bone mass, reached sometime between 15 and 30 years of age, and reducing the rate of bone loss in later adult years are the major factors influencing risk of osteoporosis (6). Because much of genetically determined peak bone mass is accumulated during the first two decades of life, childhood and adolescence are critical times to optimize skeletal health (40,41). Scientific evidence supports a beneficial role for dairy foods and dairy food nutrients such as calcium in bone health (6,40). Health professional organizations such as the American Academy of Pediatrics (41), the American Dietetic Association (42), and the U.S. Surgeon General (6) recognize the importance of calcium and calcium-rich foods such as milk, cheese, and yogurt for children’s and adolescents’ bone health.
The 2005 Dietary Guidelines for Americans states that "the consumption of milk products is especially important for children and adolescents who are building their peak bone mass and developing lifelong habits."
Research carried out at Ohio State University provides support for a positive effect of calcium and dairy products on bone mineral density in adolescent girls aged 10 years and followed for seven years (43,44). To learn more about nutritional influences on peak bone mass, the researchers conducted a long-term randomized clinical trial comparing calcium supplements (1,000 mg/day plus 881 mg/day dietary calcium) with a placebo (785 mg dietary calcium) (43). In addition, a group of girls participated in an observational study in which calcium intake (1,213 mg/day) was provided by dairy products (43). Both calcium and dairy products improved bone mass accrual, leading to a higher peak bone mass (43). While calcium supplementation and dairy products had a positive influence on bone mineral density of the hip and forearm, dairy products were also associated with a higher bone mineral density of the spine (43). Calcium influenced volumetric bone density, but dairy products had an additional impact on bone growth and bone expansion, perhaps due to the calcium and protein content of dairy products (43). In the randomized clinical trial, calcium supplementation had a significant beneficial effect on bone density during the pubertal growth spurt (ages 8-13), a time during which approximately 37% of the entire adult skeletal mass is accumulated (44).
A study of 80 British adolescent girls found that bone mineral density and bone mineral content were greater in those who increased their milk intake by an additional 1 cup/day (and increased their calcium intake from 739 mg/day to 1,125 mg/day) for 18 months compared to girls who consumed about 1/2 cup of milk/day (703 mg calcium/day) (29). Studies in Chinese children in Asia demonstrate that increasing milk intake during childhood and adolescence increases total bone mineral content, bone mineral density, and indicators of bone strength (45-48). In addition, the finding that bone mineral density and content were greater in Chinese girls receiving calcium- and vitamin D-fortified milk than calcium-fortified milk supports the role of vitamin D in promoting bone mineralization (48).
Prolonged avoidance of milk has been shown to compromise children’s bone health and increase their risk of bone fractures during childhood (49-51). When the fracture histories of 50 children ages 3 to 13 years who had avoided milk for prolonged periods were compared to fractures in a group of children born at the same time in the same city, the milk avoiders experienced more fractures, especially of the forearm (50). Also, many of the milk avoiders were overweight (50). Another study of young children with a history of avoiding milk found that reduced bone mass, height reduction, and overweight persisted over two years of follow-up (51). Further support for a beneficial effect of milk intake during childhood and adolescence on bone health and protection against fractures in later years comes from retrospective investigations in adults (52,53).
Consuming a sufficient intake of vitamin D-fortified milk and milk products (e.g., some yogurts, cheeses) is important to help protect against osteoporosis in later years and to prevent rickets (i.e., a disease characterized by soft and deformed bones) and vitamin D insufficiency in children and adolescents. While voluntary, nearly all milk sold in the U.S. is fortified with vitamin D to obtain a standardized amount of 400 I.U. per quart (40). Two cups of vitamin D-fortified milk contains 200 I.U. of vitamin D, the amount recommended for children and adolescents (40). Rickets has recently made an unexpected comeback among young children in the U.S. (54) and subclinical vitamin D deficiency has been identified in otherwise healthy adolescents (55,56). Rickets and vitamin D insufficiency are attributed in part to low intake of vitamin D-fortified milk (57).
In addition to calcium and vitamin D, other nutrients in dairy foods such as phosphorus, protein, magnesium, and zinc support children’s bone health (58). For this reason, children are encouraged to consume a varied diet consisting of nutrient dense foods – such as recommended servings of dairy foods – to support bone health (1,58).
Body Weight/Fatness. Considering the high prevalence of pediatric overweight and its implications for the development of serious diseases, both during childhood and later in adulthood, there is an urgent need to identify effective dietary and behavioral approaches. Although inconclusive, some evidence suggests that the increasing intake of high-sugar and nutrient-poor beverages relative to the decrease in milk intake may increase children’s energy consumption, potentially increasing their risk for overweight (18,37,59).
Compared to studies in adults, relatively little research has examined the relationship between calcium or dairy intake and body weight/fat in children and adolescents (18). Nearly all studies in children and adolescents are epidemiological investigations. In general, findings from these studies have shown either a beneficial or neutral relationship between calcium or dairy food intake and body weight/fat in children (18). Inconsistencies in the findings may be explained by confounding factors (e.g., energy intake, physical activity), among other variables (18).
Based on the evidence to-date, there is no scientific basis for children or adolescents who are concerned about their body weight or body fat to avoid dairy products (1,60). Considering that dairy food intake is relatively low for most American children (9) and that some evidence suggests that low intake of dairy foods may have an adverse effect on children’s body weight/fat (18,49,51,61-63), there is a critical need for more research to examine the effects of a wide range of dairy intakes on body weight/composition.
High Blood Pressure. Overweight in childhood and adolescence is strongly associated with high blood pressure in youth (16,64). In addition, other lifestyle factors including dietary intake likely influence children’s blood pressure (64). Low intake of dairy products may be a contributing factor to high blood pressure in childhood (65). In the first study to analyze the effect of food intake on blood pressure levels in children, researchers found that preschool-aged children who consistently consumed more dairy products (2 or more servings/day) with or without more servings of fruits and vegetables (4 or more servings/day) during the preschool years had smaller yearly gains in systolic blood pressure throughout childhood compared to children consuming lower amounts of these foods (65).
A new study has found that diets high in dairy foods, fruits and vegetables help children maintain a healthy blood pressure as they grow.
Although the exact mechanism for the blood pressure lowering effect of these foods is not completely understood, the researchers suggest that specific nutrients and other food components may be responsible (66). Dairy food nutrients such as calcium, magnesium, and potassium, as well
as peptides from milk proteins, have been demonstrated to lower blood pressure (66-68).
Metabolic Syndrome. Overweight and high blood pressure are components of metabolic syndrome, a condition of multiple risk factors for cardiovascular disease as well as type 2 diabetes (12,16-18). The prevalence of metabolic syndrome is high among overweight children and adolescents and it increases directly with the degree of overweight (69).
Among overweight young adults in the CARDIA (Coronary Artery Risk Development in Young Adults) study, consumption of dairy foods was inversely associated with the incidence of all components of the metabolic syndrome over 10 years, independent of other factors (70). Also, young adults participating in the Bogalusa Heart Study who had no risk factors for metabolic syndrome consumed more low-fat dairy products than those who had one or more risk factors associated with metabolic
syndrome (71). Thus, it may be that dairy intake has a beneficial effect on metabolic syndrome in children and adolescents. However, more research is needed to determine dairy’s protective effect (18).
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