Diet affects many aspects of health, including weight, athletic performance and the risk of chronic diseases such as type 2 diabetes and heart disease. Some research suggests that it could also affect mental health.
This series of Special Features looks at the science behind the most controversial nutrition-related issues, debunking myths and presenting the facts.
Anxiety disorders and depression are common conditions that affect mental health worldwide. According to the World Health Organization Trusted Source, depression could be a significant health concern worldwide as early as 2030.
It is, therefore, not surprising that researchers are constantly looking for ways to reduce mental health conditions rather than relying solely on the current treatments and medications.
A new area of research is nutritional psychiatry, which focuses on nutrition’s role in mental health issues.
Researchers are asking two questions about the role of nutrition on mental health: “Does nutrition help treat mental conditions?”
Prevention of mental health disorders
Many observational studies show a correlation between depression and diet quality.
One reviewTrustedSource of 21 different studies conducted in 10 countries concluded that a healthy dietary pattern, characterised by a high intake of fruits, vegetables, whole grains, olive oil and fish, and a low intake of animal products, was associated with reduced depression risk.
A Western-style diet, which includes a lot of red meat, processed meat, refined grains and sweets, dairy products with high fat, butter and potatoes and a lack of fruits and vegetables, was associated with an increased risk of depression.
An old review found similar results. High compliance with the Mediterranean diet was associated with a reduced risk of 32% depression.
A recent studyTrustedSource of adults over 50 found that diets rich in sugar and saturated fats were associated with higher anxiety levels.
Researchers have found similar results in children and adolescents.
A review of 2019 Trusted Source 56 studies, for example, found that a diet high in healthy foods such as fish, olive oil, nuts, legumes and dairy products reduced the risk of depression among adolescents.
It is important to remember that observational studies may show an association, but they do not prove cause and effect.
Even with randomized controlled studies, nutrition research has several limitations, such as difficulty measuring food intake.
Researchers rely on participants to recall what they ate in the past days, weeks or months. However, no one has a perfect memory.
Treatment of mental health disorders
Research into the effectiveness of dietary interventions in treating mental health issues is still relatively new.
The SMILES TrialTrusted Source is one of the first randomized, controlled trials that examined the role of diet on depression.
Over 12 weeks, 67 people with depression, moderate or severe, received dietary counselling or supported socially in addition to the current treatment.
Die dietary intervention was similar in that it focused on vegetables, fruits and whole grains. It also included oily fish, extra virgin olive oils, beans, and nuts. The diet allowed moderate amounts of dairy and red meat.
The diet group showed a significant improvement in depression symptoms at the end of the research. The gains were still substantial, even after scientists considered confounding factors, such as body mass index (BMI), smoking, physical activity and smoking.
Only 8% of the individuals in the control groups achieved remission compared to 32% of the group that followed the diet.
SMILES was a short-term, small study. To apply the findings of this study to a broader population, it is necessary to conduct more extensive and longer-term studies.
It is essential to replicate the results because not all studies agree with them. In a studyTrustedSource, which recruited 1,025 adult participants with obesity or overweight and mild to moderate depressive symptoms, the researchers examined both the effects of a multi-nutrient and food-related behaviour activation on mental outcomes.
After 12 months, the scientists found no significant difference between depressive episodes and placebos.
A meta-analysis of Trusted Source in the same year found that dietary interventions reduced depression symptoms but not anxiety.
The existing research cannot provide solid conclusions, significantly, as the types of dietary interventions investigated in the studies vary greatly.
In general, there is a need for more research on specific dietary patterns and the treatment of mental disorders. There is a particular need for a more standard definition of a healthy diet and more significant, longer-term studies.
What are supplements?
Scientists are also interested in the effects of individual nutrients, in the form of dietary supplements, on mental health.
Researchers have found linksTrusted Source between low folate, magnesium and iron, zinc and vitamin B6, B12 and D, and worsened mood, anxiety and depression.
There is no conclusive evidence that consuming additional nutrients as supplements will improve mental health.
If someone is magnesium deficient, taking a supplement could help alleviate symptoms. However, if someone gets enough magnesium through their diet, it could be clearer whether a supplement can benefit them.
Omega-3 fatty acid is an essential nutrient that plays a significant role in brain development. An article published in Frontiers in Physiology Trusted Source discusses how these fatty acids reduce inflammation.
Scientists have studied the effects of omega-3s on mental health due to their anti-inflammatory properties and importance for brain health.
Although more research is needed, 2018TrustedSource and 2019, TrustedSource reviews of randomized controlled trials found that omega-3 supplements effectively treat anxiety and depression among adults.
As with vitamins and minerals, it could be clearer if omega-3 supplements can improve mood for most people or if they are only effective for those who consume the least omega-3s.
We still need to learn more about supplements for mental well-being, such as the best doses for different populations and their long-term effectiveness and safety.
Experts recommend obtaining the most nutrients by eating a healthy and varied diet. If you are concerned that diet alone cannot meet your nutrient requirements, speak to your doctor about whether supplements could help.
Why? is the big question
Although more research is needed, observations suggest that there may be a connection between the food people eat and their mental well-being. It is still being determined why nutrition could have such an effect.
There are many theories about how diet can affect mood and the risk of depression or anxiety.
Scientists believe specific dietary patterns’ inflammatory effects may help explain the link between diet and mental well-being.
The authors of journal articles in Frontiers in ImmunologyTrusted Source and Current NeuropharmacologyTrusted Source discuss this relationship.
Diets that promote mental health, for example, tend to include many fruits, vegetables, whole grains, and healthy fats. These foods are rich in anti-inflammatory compounds.
A reportTrusted Source supports this theory. Diets rich in anti-inflammatory and antioxidant foods are associated with a lower risk of depression.
The exact relationship between inflammation and mental health and diet is still not fully understood.
Another possible explanation is a diet that affects the bacteria in your gut (also known as the microbiome).
Ongoing researchTrustedSource found a strong connection between gut health and brain function. Healthy bacteria in the gut can produce up to 90% of the neurotransmitter serotonin.
Further, early research (Trusted Source) shows that a healthy microbiome in the gut may be linked to a lower rate of depression.
This theory offers a good explanation of how our diet may affect our mental health.
There is also the possibility that diet has a more indirect impact on mental health.
People with healthy diets may also be more likely to adopt behaviours linked to a lower risk of mental disorders, like engaging in regular physical activities, maintaining good sleep, and abstaining from smoking.
The Complexity of Mental Health
You should be aware that there are many factors which can affect both your eating habits and your mental health.
According to MentalHealth.govTrusted Source, factors contributing to mental health conditions include biological factors, such as genetics, life experiences, and family history. Mental health can be affected by socioeconomic status, access to food, and diet quality.
Mental health can affect eating habits. You may turn to unhealthy foods such as candy or highly processed snacks when feeling angry or upset.
Many antidepressants, anti-anxiety drugs and other medications can also increase your appetite and cause cravings. Mental health issues can make it challenging to maintain a healthy diet.
While diet is essential in mental health, many other factors can also affect mood.
Ongoing research is being conducted on the effects of nutrition on mental health.
Even though more research is required, it appears that our food choices may influence our mental health.
Mental health is a much more complex issue than diet.
It is, therefore, necessary that anyone experiencing depression, anxiety or general concerns regarding their mental health work with a trusted healthcare provider to develop a customized treatment plan.