BDNF and major depressive disorder: The association between eating patterns and mental health can be explained by the association of eating low nutrient-dense foods with mental problems via the direct effect of diet on inflammatory parameters, immune system markers and biomarkers of oxidative stress responsible for mental issues like depression or anxiety and the effects of unhealthy food items like simple sugars and saturated fats on the proteins involved in the brain development like BDNF [14–18].