The association between dairy product consumption and health outcomes in children and adolescents in developed countries

Dairy products are part of a nutrient-rich and balanced diet and are associated with diets of higher nutritional quality when consumed in sufficient amounts.1,2 They contribute to positive health outcomes by providing energy, high-quality protein, micronutrients, and bioactive compounds. Micronutrients available in dairy products include calcium, phosphorus, magnesium, iodine, zinc, potassium, vitamin A, vitamin D, vitamin B12, and vitamin B2 (riboflavin). Thus, the consumption of dairy products contributes to an adequate dietary nutrient intake in children and adolescents, a healthy lifestyle, as well as beneficial health-related outcomes.

Vitamins in dairy

This article features a review by Dror and Allen (2014) which examined the correlation between dairy consumption and health outcomes in well-nourished, healthy children and adolescents in developed countries.3 In this review, a total of 2,990 scientific papers were screened. From these, 78 observational studies and intervention trials were used to obtain information on the association between dairy intake and health-related outcomes relating to dental health, bone mineralization, linear growth, body composition and adiposity or blood pressure.3

Dror and Allen (2014) – Beneficial effects of dairy products on health-related outcomes

Dental health

Dror and Allen (2014) evaluated eleven observational studies relating to dental health in children and adolescents.3 According to the review, all of these revealed that milk and/or dairy consumption (in particular yogurt and cheese) was positively associated with dental health. The data provides evidence that dairy product intake is negatively associated with dental caries or decayed, missing and filled teeth in deciduous as well as permanent teeth.3

Bone mineralization and bone health

The review also reviewed the beneficial effects of dairy products on bone health and bone mass acquisition in children and adolescents from a total of 13 observational and interventional studies.3 Correlations between dairy product intake and bone health outcomes were evaluated through the analysis of bone mineral content (regional or total body bone mineral content). Of the 13 publications reviewed by Dror and Allen (2014), 12 studies revealed evidence for a favorable effect of dairy foods on bone health and bone mass acquisition as children and adolescents with a higher intake of dairy products were found to have a higher bone mineral content or greater improvements in bone mineral content over time.3

Linear growth and development

According to the authors, the majority of studies (14 out of 17 observational and interventional studies) found that dairy product intake was positively associated with the linear growth and height of children and adolescents.3 The remaining three studies did not find a significant correlation between dairy consumption and height or growth.3 The positive association between dairy product consumption and height and growth is in line with results from a meta-analysis of twelve interventional studies in children and adolescents from both developed and developing countries.4 The results of this meta-analysis suggest that a daily supplementation of about 245 mL milk is associated with an annual growth increase of about 0.4 cm (with a greater effect in peripubescent children and those with reduced baseline height-for-age values).4

Body composition and adiposity

With regard to the increasing problem of childhood obesity, the correlation between milk and dairy product consumption and body mass index (BMI), body fat or energy balance was evaluated by Dror and Allen (2014). According to the authors, the review showed that 34 out of 35 included observational and interventional studies reported a neutral or negative association between dairy intake and BMI, body fat, or energy balance.3 Only one cross-sectional study showed a positive association between dairy consumption and BMI. The findings of this review suggest that children who consume dairy products are less likely to be overweight and obese, and more likely to have a balanced body composition. Other recent studies that investigated the relationship between beverage intake patterns and body composition support the conclusions drawn by Dror and Allen. In the prospective Framingham Children’s Study, Hasnain and colleagues (2014) found that children who consumed the lowest amount of milk during early childhood had a higher body fat composition later in adolescence compared to those children who consumed a higher amount.5 Another study by Vanselow and colleagues (2009) also showed that among adolescents, those who consumed little or no white milk gained considerably more weight than those who consumed white milk.6 In addition, the Healthy Start Study was carried out by Zheng et al (2015) to investigate the influence of replacing sugary drinks with other beverages on body weight in children with high predisposition for future overweight. This randomized controlled trial showed that replacement of sugary beverages with milk was inversely associated with body weight gain as measured by changes in BMI z-score, waist circumference and sum of four skinfolds.7,8

Blood pressure and cardiovascular health

There is a comprehensive body of evidence from literature that suggests that dairy consumption is inversely associated with elevated blood pressure in adults.9 However, the data is limited for children and adolescents. The review by Dror and Allen (2014) found only two studies that evaluated the correlation between dairy product consumption and blood pressure in children. According to the authors, these studies suggest that dairy intake in early childhood (18-59 months of age) is associated with reduced blood pressure in middle childhood or early adolescence which corroborates the results found in adults.3

Declining trend in dairy foods consumption and factors influencing this trend

Several developed countries recommend a daily consumption of milk and dairy products by children and adolescents due to its nutrient dense properties. Some countries based their recommendations on dietary intakes for calcium to meet the nutritional needs of children and adolescents. The recommendations for dairy food intake in developed countries range from a daily intake of approximately two to three servings (about 500 mL) for children up to 9 years of age to approximately three to five servings (more than 600 mL) for adolescents.3

However, despite such recommendations and favorable outcomes of dairy intake, national dietary surveys and studies of dairy product consumption have shown that a proportion of children and adolescents in developed countries fail to meet the national intake recommendations. In addition to detecting this insufficiency, national surveys also serve to identify factors relating to the reduced intake.

In this way, several individual and environmental factors have been suggested to impact dairy consumption in childhood as was reviewed by Dror and Allen (20014):3

  • Gender – The amount of dairy products consumed by male children is greater than that of girls.
  • Age – A downward trend in the consumption of dairy products with age through middle childhood and early adolescence can be observed.
  • Parental influence – Parental attitude and practice on dairy consumption impacts the dairy intake behavior of children as milk consumption is reduced in children within families with limited expectations for drinking milk as well as in children whose parents consume dairy foods infrequently.
  • Alternative beverages – Milk may be substituted with alternative beverages as a decline in milk intake is associated with an increased intake of sweetened beverages.10
  • Dietary pattern – Breakfast-consuming children and adolescents have a higher intake of milk than non-consumers of breakfast.

Identifying factors that influence children’s and adolescents’ dairy product intake is essential for gaining a better understanding of the secular trend and will help address it in the future.

Conclusions

Pertinent knowledge gaps in the correlation between dairy product intake, key nutrient status and health outcomes warrant further research. While several studies suggest that key nutrients available in dairy foods play a role in meeting the recommended intake levels of children and adolescents, the relationship between dairy consumption and nutrient status remains unclear. To fully understand the direct relationship between diary consumption and nutrient adequacy, future studies need to complement the current data from dietary surveys by directly measuring the nutrient status in humans through biomarkers.

Likewise, more studies (in particular randomized controlled trials) have to be conducted to investigate the beneficial effects of dairy on health-related outcomes. Some of the reviewed studies exhibited differences in the study design which can lead to variations in the results.

Finally, a trend of declining dairy product consumption by a proportion of children and adolescents who failed to meet the national intake recommendations can be observed. Whether this trend is global or specific to children and adolescents in developed countries has yet to be elucidated. The identification of more factors that affect the consumption of dairy foods would allow a more comprehensive understanding of the reasons behind the waning intake of dairy foods during mid-childhood and early adolescents.

References

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  8. Zheng M, Rangan A, Allman-Farinelli M, Rohde JF, Olsen NJ, Heitmann BL. Replacing sugary drinks with milk is inversely associated with weight gain among young obesity-predisposed children. Br J Nutr. 2015:1-8.
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