Researchers have found an association between high protein intake and decreased symptoms of depression

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Appropriate availability of macro- and micronutrients has an important impact on cognitive performance, mood and mental health.

Food is vital for survival, provides the body with energy, is important for growth and contributes to the fact that people stay healthy and feel well (Eaton et al., 2020). The food we eat is comprised of different components, including macro- and micronutrients.

Macronutrients (carbohydrates, proteins, fats) are nutrients that humans need a lot of, whereas micronutrients (e.g., vitamins, minerals) are needed in relatively small amounts. Other important components of our daily food include fibre, water and antioxidants (Eaton et al., 2020).

Appropriate availability of macro- and micronutrients have an important impact on the composition, structure and function of the brain (Gomez-Pinilla, 2008). As a consequence, the quality of nutrition is related to cognitive performance, mood and mental health (Adan et al., 2019).

Previous research revealed that dietary behaviour of people with mental health issues is often inadequate due to poor food choices (Rao et al., 2008). For instance, people with severe mental illnesses (SMIs) – including schizophrenia, major depressive disorder (MDD) and bipolar disorder – were shown to have excessive caloric intake, a low-quality diet, and poor nutritional status compared to the general population (Firth et al., 2018).

Nutrition has also received increased attention as a key modifiable factor in the prevention and treatment of depressive disorders (Akbaraly et al., 2009; Chopra et al., 2021). For instance, data from the Women’s Health Initiative Observational Study (N = 876′618 participants) showed that a higher dietary glycemic index (GI; ranking of food that contains carbohydrates in accordance to how much it increases blood glucose levels after consumption compared to reference food) was associated with increased odds of incident depression.

A similar relationship was found for dietary added sugars and nonwhole/refined grain consumption, whereas higher consumption of lactose, fibre, non-juice fruit, and vegetables were associated with lower odds of incident depression (Gangwisch et al., 2015). A UK Biobank analysis of 69′843 adults corroborated that the presence of MDD was associated with higher total energy intake, more carbohydrates, sugar, total fat, and saturated fat.

In a systematic review of 9 cross-sectional and 4 cohort studies, the risk of depression was markedly increased among participants with an unhealthy diet (e.g., low fruit, vegetables, fish and nonwhole grain consumption) (Lai et al., 2014). This is in line with 2 meta-analyses (Lassale et al., 2019; Psaltopoulou et al., 2013), showing that a Mediterranean-style diet – defined as a healthy eating plan that contains a lot of plant-based foods, olive oil as main source of added fat, moderate consumption of fish, seafood, dairy and poultry, and low intake of red meat and sweets (Davis et al., 2015) – was associated with a reduced risk of depression.

Another meta-analysis (Salari-Moghaddam et al., 2019) of cohort studies further linked increased dietary GI and odds of depression. Recently, a quantitative analysis of 16 randomized-controlled trials showed that dietary interventions have the potential to reduce incidence of future depression (Firth et al., 2019).

Studies have also shown that in high-income countries the association between nutrition and depression is independent of socioeconomic status, education and other potential confounders, and not due to reversed causality (Jacka et al., 2015). Taken together, there is growing evidence from different countries that among adults a good-quality diet is a protective factor for future depression (Jacka et al., 2017).

Solid empirical evidence also exists for adolescent populations. For instance, a large-scale study with almost 2′900 Australian adolescents (14 years old) found that an unhealthy Western diet was associated with more total mental health problems after adjustment for various confounders (Oddy et al., 2009).

Another study with 1′095 Norwegian adolescents (12–13 years old) suggested that a healthy, varied diet was associated with a lower likelihood of any psychiatric disorders and hyperactivity-inattention disorders (Oellingrath et al., 2014). Similar relationships between dietary aspects (e.g., regular breakfast consumption, vegetable consumption, snacking, amount of animal foods) were observed in adolescents from China (Weng et al., 2012), Japan (Tanaka & Hashimoto, 2019), Malaysia (Tajik et al., 2016), and New Zealand (Kulkarni et al., 2015). Studies with a specific focus on depressive symptoms also confirmed this relationship.

Thus, a study with 7′114 Australian adolescents revealed a negative association between diet quality and depressive symptoms that was independent of potential demographic, socioeconomic and family-related confounders (Jacka et al., 2010). In summary, based on a review of children and adolescent research, O’Neil et al. (2014) concluded that if studies had adequate methodological quality, all but one corroborated that a good-quality diet was associated with better mental health. Nevertheless, effect sizes were generally small if significant relationships were identified (Khalid et al., 2016).

The critical role of nutrition for elite athletes was recognized early on (Brotherhood, 1984). Carbohydrates are essential for high power outputs required by athletic sports. Muscle glycogen is a limiting factor in hard physical exercise because it is stored in limited amounts, utilized rapidly during intense exercise, and after depletion to low levels in the active muscle, leads to fatigue (ACSM, 2016).

Additionally, during (hard) physical exercise, protein is degraded and amino-acids are oxidized, whereas during muscle building training protein is retained. Therefore, minimal carbohydrate and protein requirements might be higher among elite athletes than in the normal population (ACSM, 2016).

Not surprisingly, therefore, the American College of Sports Medicine (ACSM) (ACSM, 2016) highlighted that an appropriate diet is critical for competitive performance in many sports disciplines, to decrease the risk of injury, and to contribute to important determinants of performance such as body weight and composition (Beck et al., 2015).

Nutrition can also influence athletes’ susceptibility to infection and their response to infections, as both macro- and micronutrients are involved in multiple immune processes (e.g. immune cell metabolism, protein synthesis, antioxidant defense) (Walsh, 2019).

Furthermore, during recent years, researchers and international sport organizations have shown increasing interest in the mental health of elite athletes (Küttel & Larsen, 2020). This trend is mirrored in recent position statements of the International Society for Sport Psychology (Henriksen et al., 2020), the European Federation of Sport Psychology (Moesch et al., 2018), the American Medical Society for Sports Medicine (Chang et al., 2020) and the International Olympic Committee (Reardon et al., 2019).

Nevertheless, in 2 position statements, the role of an appropriate diet for mental health was only discussed very marginally (Henriksen et al., 2020; Moesch et al., 2018), whereas in the other 2 position statements, a specific subsection was devoted to eating disorders (including anorexia nervosa, bulimia nervosa and binge eating disorder) (Chang et al., 2020; Reardon et al., 2019). Nevertheless, the role of a healthy diet for the mental health of athletes in general was not taken into account either.

This is a clear indication that the role of nutrition on athlete mental health is currently understudied (de Souza et al., 2019). To our knowledge, the only study available so far showed a relationship between unhealthy dietary habits and increased psychological distress in male (but not female) US national collegiate athletes (de Souza et al., 2019).

Conclusion

In Swiss adolescent elite athletes, dietary intake needs improvement as we observed several deviations from DACH recommendations. In elite athletes, higher protein consumption was prospectively associated with lower depressive symptom severity at follow-up.

More experimental research is needed. For instance, future investigations could examine whether and to what degree nutrition education and dietary modification can be used among elite athletes as a cost-effective strategy for the prevention of depression.


reference link: Original Research: Open access.
Macronutrient intake as a prospective predictor of depressive symptom severity: An exploratory study with adolescent elite athletes” by Markus Gerber et al. Psychology of Sport and Exercise

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