Executive functions are involved in regulating thoughts and behaviors important to preadolescents, including greater self-regulation, thereby reducing impulsivity and risky behaviors, as well as enhancing learning and academic achievement. Executive functions are choreographed largely by the prefrontal cortex and its related neural circuitry. It is plausible that nutritional factors alter structural and/or functional aspects of executive function–related prefrontal cortex neural circuitry and, thereby, improve the efficiency of these circuits or the rate at which executive functions mature (1).

    A randomized, parallel-group, double-blinded, placebo-controlled study examined the executive functions of 122 preadolescents (58 females) aged 9–13 before and after the 9-month intervention of consuming food products with either: 1) whole egg powder; 2) milk powder; or 3) gelatin as a placebo, all matched on macronutrient content and used as replacements for commonly consumed foods (i.e., waffles, pancakes, macaroni and cheese, ice cream, and brownies). The primary outcomes were measures of executive function: mental flexibility, working memory, selective attention, and inhibitory control (1).

 

    A statistically significant effect for selective attention and inhibitory control was found (p = 0.049) for the milk group. Other comparisons were statistically insignificant. This study showed that the consumption of foods with added milk powder as a replacement for snacks or meals for 9 months improved selective attention and inhibitory control in preadolescents (1).

 

    Experiments have confirmed that negative expectations or conditioning effects can produce nocebo responses in cognitive performance outcomes. The nocebo effect is the opposite of the placebo effect. It describes a situation where a negative outcome occurs due to a belief that something negative (i.e. the intervention side effects) will occur. Inhibitory control can mediate nocebo effects, for example, a lower inhibitory control could have allowed others’ negative beliefs to have a larger impact on the self, which would result in low expectations for performance on this outcome and performance itself (1).

 

    Greater self-regulation/inhibitory control can be very important for preadolescents’ mental health stability. With many negative impacts from peer pressure and social influences these days, a young person with a stronger mental mindset can expect and achieve more for him or herself. This study's results suggested that milk powder supplementation may benefit children in their executive function development.

 

    Another randomized, case-controlled study of 4 schools tested 469 students (mean age of 9 years), examining the effects of 3 months of supervised consumption of 250 ml of milk at school on fluid intelligence.  Fluid intelligence is defined as reasoning ability, and the ability to generate, transform and manipulate different types of novel information in real-time. In this study, milk supplementation significantly improved intelligence quotient, both verbal and non-verbal skills. The intelligence quotient (IQ) scores for the boys were increased from 92 ± 13 and 87 ± 10 for the control and milk group at the start of the study to 94 ± 14 and 96 ± 11, respectively, at the end of the study. The intelligence quotient scores for the girls were 84 ± 14 and 89 ± 9 for the control and milk group at the start of the study, and the scores increased to 90 ± 15 and 99 ± 13, respectively, at the end of the study. School performance increased in the intervention group but the small significant grade point average increase was only among girls (2).

 

    The nutrient content of milk might be responsible for this intelligence quotient improvement. These days sugar-sweetened beverages are consumed in high amounts worldwide. They are the main competitors of milk for school-aged children to drink on a regular basis. Sugar-sweetened drinks beyond the normal intake could increase the rate of overweight and obesity while dairy products like milk have weight control effects. It is important to teach children how to select beverages that offer energy and nutrient content at the same time.

 

    One cross-over study looked at the cognitive function in 84 children ages 8–12 (45 female, 39 male) after two-morning testing sessions after fasting overnight. Participants drank either 237 mL of 1% milk or apple juice in one testing session and then drank the other drink in another session. Behavioral measures and complex attentional and executive function tasks were assessed at baseline, 30, 90, and 120 min post-ingestion. Participants with fasting glucose levels above 89.91 mg/dL responded more quickly in an inhibitory control paradigm following milk. Females performed faster on a vigilance task, but less accurate in a working memory paradigm after milk versus juice. No effects were found for on-task behavior. A vigilance task requires a person to maintain attention the whole time he or she is working, always being watchful (3).

 

    The results from this study (3) agree with the previous findings: supplementing preadolescents’ diet with milk powders for 9 months resulted in greater self-regulation/inhibitory control function (1), and supplementing schoolchildren’s diet with dairy milk may improve intelligence quotient development (2). Many studies have shown the long-term benefits of consuming dairy products as part of a regular diet on early cognitive function development, for example, children who consume dairy in their toddler years would have better verbal and nonverbal intelligence at ten years of age (4). Dairy milk is a nutritious drink for optimizing cognition and behavior in school-aged children.

 

References:

1.            O'Connor PJ, Chen X, Coheley LM, Yu M, Laing EM, Oshri A, Marand A, Lance J, Kealey K, Lewis RD. The effects of 9 months of formulated whole-egg or milk powder food products as meal or snack replacements on executive function in preadolescents: A randomized, placebo-controlled trial. Am J Clin Nutr. 2022 Dec 19;116(6):1663-1671. doi: 10.1093/ajcn/nqac281. PMID: 36173384.

2.            Rahmani K, Djazayery A, Habibi MI, Heidari H, Dorosti-Motlagh AR, Pourshahriari M, Azadbakht L. Effects of daily milk supplementation on improving the physical and mental function as well as school performance among children: results from a school feeding program. J Res Med Sci. 2011 Apr;16(4):469-76. PMID: 22091261; PMCID: PMC3214350.

3.            Anderson JR, Gunstad J, Updegraff J, Sato A, Hagerdorn PL, Spitznagel MB. Biological sex and glucoregulation modulate postprandial cognition following dairy milk and fruit juice in healthy school-age children. Nutr Neurosci. 2020 May;23(5):374-383. doi: 10.1080/1028415X.2018.1507963. Epub 2018 Aug 10. PMID: 30095386.

4.            Nyaradi A, Li J, Hickling S, Whitehouse AJ, Foster JK, Oddy WH. Diet in the early years of life influences cognitive outcomes at 10 years: a prospective cohort study. Acta Paediatr. 2013 Dec;102(12):1165-73. doi: 10.1111/apa.12363. Epub 2013 Aug 14. PMID: 23879236.

 

Keywords: Milk, Dairy, Cognitive Function, Executive Function, Intelligence, IQ, School Performance, Children, School-aged Children, Adolescents, Preadolecents, Inhibitory Control, Nutrition, Health, 牛奶，奶制品，认知功能，执行功能，智力，智商，学校表现，儿童，学龄儿童，青少年，青春期前儿童，抑制控制，营养，健康

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