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The role of nutrition in mental health
According to the National Institute of Mental health, the two major causes of disability worldwide are anxiety, closely followed by depression. In 2010 a meta-analysis published in JAMA1 found that while there are substantial benefits for anti-depressant medications in those with severe depression, the benefits are either mild or non-existent for those with milder forms of the condition. Considering the human and economic costs, there is a need to find alternatives for mental health issues. As poor nutrition has been considered as a risk factor for depression, this review aims to evaluate the effects of dietary patterns in mental health.
Dietary patterns and mental health
The role of the Mediterranean diet in heart disease, cancer and life expectancy is well known2. Recent data now suggests a beneficial role for this diet in mental health. Studies in the United Kingdom and Spain found that a Mediterranean diet rich in fruits, vegetables and seafood is associated with a decreased risk of depressive symptoms compared to a diet rich in meat and highfat and sweet products3-4. Foods included in the Mediterranean diet provide rich sources of fibre, antioxidants, omega-3 polyunsaturated fatty acids, magnesium, zinc and other nutrients important for mental health.
Foods with a high glycemic index/load (refined foods and sweetened beverages) are digested quickly and cause a spike in blood sugar and insulin. This fluctuation in blood glucose has negative effects on mood5-6. The same is observed when skipping meals or consuming a high glycemic diet7.
Caffeine, consumed not only in coffee and tea but now more often with “energy” drinks, is also well known to be associated with anxiety, so that its consumption should be decreased for people with anxiety disorders.
Micronutrients and mental health
As B-vitamins play a role in plasma homocysteine concentration (B6) and in the production of neurotransmitters (B12), deficiency in these vitamins can represent a risk factor for depression, cognitive dysfunction/decline, and memory loss8-12. Folate can enhance antidepressant therapy13 so that prevention should take into account folate deficiency. Deficiency in vitamin D, found in fish, can also have an impact on executive cognitive functions and depression14.
Iron deficiency is the most common deficiency worldwide, particularly affecting women and young children15. Iron plays a role in neurotransmitter synthesis and function so that deficiency can cause fatigue, poor concentration, and serve as a risk factor for depression16-17.
Zinc is involved in cellular metabolism, immune function and DNA synthesis18; deficiency can cause behavioral and sleep disturbances, as well as the loss of sex drive19. Magnesium is involved in numerous biochemical reactions in the body (nerve function, heart rhythm, blood pressure, immune response and insulin regulation)18. Deficiency is associated with anxiety, irritability and sleep disorders20.
Omega 3 Fatty Acids are essential fatty acids that must be obtained in the diet. Their role in cellular function, vision and nervous system, can explain why deficiency in omega 3 fatty acids may be a risk factor for depression21-23.
“The way we eat affects the way we feel”
This sentence sums up what is developed in this review. If dietary supplements, such as B-vitamins or omega 3 fatty acids, can help to prevent or ease depressive symptoms, dietary recommendations should be promoted to help ensure the mental health of the public. A diet rich in fruits, vegetables, whole grains and seafood, close to the Mediterranean diet, could improve nutrient status and prevent mood disorders and mental health diseases.
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