Dairy Consumption in Youth Linked with Better Mental Health

 Written by: Alice Callahan, PhD | SPLASH! Issue # 113 | 2023

Children grow up hearing that milk and other dairy foods can help them develop strong and healthy bones. But could dairy also be good for kids’ brains—and their mental health? Researchers have been working to answer this question, which has taken on greater urgency given the rise in youth struggling with mental health [1]. According to the World Health Organization, about 14% of 10- to 19-year-olds globally have a mental health condition, with anxiety and depression being most common.

In general, a healthier dietary pattern has been associated with a reduced risk of depression [2], but studies attempting to tease out the specific effects of dairy products have found mixed results. A recent systematic review of 13 studies in adults reported that most found either no association or results that varied based on type of dairy product, gender, or population group [3]. Similarly, several studies in youth have found no relationship between dairy consumption and mental health, but recent reports from Iran and Korea found a positive association between dairy consumption and mental health in adolescents [4,5].

Seeking to investigate this relationship among youth in China, researchers Zhiyong Zou and Yanhui Dong from the Institute of Child and Adolescent Health at Peking University, along with their colleagues, recruited students enrolled in Beijing schools to participate in a cross-sectional study [6]. The study included 1,353 youth between the ages of 7 and 17 years old. Students were asked to complete questionnaires about their physical activity, diet, and symptoms of depression and anxiety. Their parents also provided background information, including parental education level, household income, single child status, and whether parents were smokers.

The study, which was published in the Journal of Affective Disorders in December 2022, found that about 54% of participating youth consumed dairy products habitually, on six or more days per week. Another 35% had dairy products on two to five days per week, and 11% had dairy on just one day per week or not at all.

When the researchers looked at the study participants’ mental health, they found that the habitual dairy consumers had lower rates of depression and anxiety than those who consumed less dairy. For example, among those who consumed dairy on six or more days per week, about 12% had symptoms of depression, and 26% had symptoms of social anxiety. In comparison, 21% of those who had dairy just once per week or not at all had symptoms of depression, and 40% had symptoms of anxiety.

The children and adolescents in the study who consumed more dairy products also appeared to be more advantaged and have healthier lifestyles in other ways. On average, they ate more fruits and vegetables, were younger and more physically active, and their parents were better educated. However, when the researchers accounted for these differences, they found that dairy consumption was still associated with lower odds of depression and anxiety, though the relationship was somewhat attenuated.

The results were surprising and were strengthened by the large number of children and the wide age range included in the study, wrote Jieyu Liu, a doctoral student at Peking University and the first author of the study, in an email interview with SPLASH! Milk Science Update. However, the study also had several limitations. For example, the data were self-reported by students in brief questionnaires, and more objective and detailed measures of diet and physical activity, and clinical assessments by mental health professionals could have yielded more accurate results.

In addition, the observational design of this study means that its findings can only identify correlations—in this case, between dairy consumption and a lower prevalence of symptoms of depression and anxiety—and it cannot provide direct evidence that dairy consumption prevents depression or anxiety. There could be alternative explanations for this correlation, Liu acknowledged, and the study did not measure several important and known risk factors for adolescent depression, such as family history of depression, exposure to bullying, growing up in a negative family environment, experiencing trauma, or substance use [7]. Without a better accounting of the factors contributing to youth mental health, it’s difficult to draw conclusions about how dairy intake may affect risk of depression or anxiety.

That said, there are several possible mechanisms for how dairy foods might support better mental health. For example, they are good sources of several nutrients known to play roles in brain health: calcium regulates neurotransmitter release; milk proteins are rich in the amino acid tryptophan, a precursor to serotonin; and vitamin D may protect against inflammation and oxidative stress. The type of dairy product may also matter. A recent study in Finnish adults found that only high-fat dairy consumption, and not low-fat or total dairy intake, was associated with a lower risk of depressive symptoms [8]. And a meta-analysis published earlier this year concluded that eating fermented dairy products like yogurt and cheese was associated with a significant decrease in the risk of depression, perhaps mediated by live microbes in these foods and their effect on the gut-brain axis [9].

Future research on this question should include more detailed data on the types and amounts of dairy products consumed, as well as other nutritional factors, such as intake of red meat, snack foods, and fast foods, Lui wrote in the email interview. Well-designed prospective studies and intervention trials are also needed to better understand the complex relationships between diet and mental health.

References

1. Young people’s mental health is finally getting the attention it needs. Nature. 2021 Oct 598(7880):235-236.
2. Selvaraj R, Selvamani TY, Zahra A, Malla J, Dhanoa RK, Venugopal S, Shoukrie SI, Hamouda RK, Hamid P. Association between dietary habits and depression: A systematic review. Cureus. 2022 Dec 14(12):e32359.
3. Hockey M, McGuinness AJ, Marx W, Rocks T, Jacka FN, Ruusunen A. Is dairy consumption associated with depressive symptoms or disorders in adults? A systematic review of observational studies. Critical Reviews in Food Science and Nutrition. 2020;60(21):3653-3668.
4. Khayyatzadeh SS, Shafiee M, Far PE, Ziaee SS, Bagherniya M, Ebrahimi S, Boromand N, Ferns GA, Ghayour-Mobarhan M. Adherence to a healthy dietary pattern is associated with less severe depressive symptoms among adolescent girls. Psychiatry Research. 2019 Feb 272:467-473.
5. Park S, Rim SJ, Lee JH. Associations between dietary behaviours and perceived physical and mental health status among Korean adolescents. Nutrition & Dietetics. 2018 Jul 75(5):488-493.
6. Liu J, Chen M, Ma Y, Ma T, Gao D, Li Y, Wang X, Chen L, Ma Q, Zhang Y, Ma J, Zou Z, Dong Y. Habitual dairy consumption is inversely associated with depressive and social anxiety symptoms among children and adolescents aged 7-17 years: Findings from a cross-sectional study in Beijing, China. Journal of Affective Disorders. 2022 Dec 319:309-317.
7. Wahid SS, Ottman K, Hudhud R, et al. Identifying risk factors and detection strategies for adolescent depression in diverse global settings: A Delphi consensus study. Journal of Affective Disorders. 2021 Jan 279:66-74.
8. Hockey M, Mohebbi M, Tolmunen T, Hantunen S, Tuomainen T, Macpherson H, Jacka FN, Virtanen JK, Rocks T, Russunen A. Associations between total dairy, high-fat dairy and low-fat dairy intake, and depressive symptoms: findings from a population-based cross-sectional study. European Journal of Nutrition. 2023 Feb 62(1):227-237.
9. Luo Y, Li Z, Gu L, Zhang K. Fermented dairy foods consumption and depressive symptoms: A meta-analysis of cohort studies. PLoS ONE. 2023 Feb 18(2):e0281346.

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