Table 8.

Summary of the effects of the described nutrients on the risk of depression.

Nutrient	Conclusions
Proteins	Higher total protein consumption as well as that specifically derived from milk and dairy products might potentially lower the susceptibility to depressive symptoms. No benefit has been shown for protein intake from animal sources [47,48]. A beneficial effect of a higher supply of tryptophan in the diet has been shown to decrease the risk of depression [49,50,51]. A diet with an increased supply of protein relative to other macronutrients may have a beneficial effect on the risk of depression in adults who do not have any chronic diseases [58,59,60,61].
Fats	No association has been observed between total fat consumption and the manifestation of depressive symptoms [52,53,59], although not all results are conclusive [58,60].
Carbohydrates	Greater exposure to added sugars, low-quality carbohydrates, and low dietary fibre intake have been shown to correlate with a higher risk of depression [54,57]. No significant association was observed between the dietary glycaemic index and the dietary glycaemic load and the likelihood of depression [57].
Water	To date, it has not been conclusively demonstrated that dietary water intake directly affects the risk of depression; however, dehydration can exacerbate, for example, fatigue and depression. Therefore, it is worth ensuring that the body is adequately hydrated to avoid the negative effects of dehydration [46,62].
Polyunsaturated fatty acids	All the publications cited showed a beneficial effect of increased omega-3 fatty acid intake to prevent the onset of depressive symptoms in different groups [70,71,72,73,74,75].
Vitamins of the B group	Low dietary and/or serum levels of vitamins B1, B6, B9, and B12 have been associated with a higher prevalence of depressive symptoms [97,98,99,100,101,102,103]. The findings suggest that the intake of adequate amounts of B vitamins may have a positive impact on mental health and reduce the risk of depressive symptoms.
Vitamin D	Depressed patients have significantly lower serum vitamin D levels [58,118]. It has been shown that approximately 80% of depressed patients do not take adequate daily doses of vitamin D [118].
Mineral Components	Dietary deficiencies in magnesium, zinc, selenium, copper, and manganese have been associated with a greater likelihood of depression [147,148,149,150,151,152,153,154,155,156,157,158,159,160]. Both excess and deficiency of copper and iron may affect the risk of depression [135,145,154,155].