Diet influences numerous aspects of health, including weight, athletic performance, and risk of chronic diseases, such as heart disease and type 2 diabetes. According to some research, it may affect mental health, too.
Anxiety and depression are among the most common mental health conditions worldwide. According to the World Health Organization (WHO), depression could be one of the top health concerns in the world by 2030.
Therefore, it is not surprising that researchers continue to search for new ways to reduce the impact of mental health conditions, rather than relying on current therapies and medications.
Nutritional psychiatry is an emerging area of research specifically looking at the role of nutrition in the development and treatment of mental health problems.
The two main questions that researchers are asking in relation to the role of nutrition in mental health are, “Does diet help prevent mental health conditions?” and, “Are nutrition interventions helpful in the treatment of these conditions?”
Several observational studies have shown a link between overall diet quality and the risk of depression.
For example, one review of 21 studies from 10 countries found that a healthful dietary pattern — characterized by high intakes of fruit, vegetables, whole grains, olive oil, fish, low fat dairy, and antioxidants, as well as low intakes of animal foods — was associated with a reduced risk of depression.
Conversely, a Western-style diet — involving a high intake of red and processed meats, refined grains, sweets, high fat dairy products, butter, and potatoes, as well as a low intake of fruit and vegetables — was linked with a significantly increased risk of depression.
An older review found similar results, with high compliance with a Mediterranean diet being associated with a 32% reduced risk of depression.
More recently, a study looking at adults over the age of 50 years found a link between higher levels of anxiety and diets high in saturated fat and added sugars.
Interestingly, researchers have noted similar findings in kids and teenagers.
For example, a 2019 review of 56 studies found an association between a high intake of healthful foods, such as olive oil, fish, nuts, legumes, dairy products, fruits, and vegetables, and a reduced risk of depression during adolescence.
However, it is important to keep in mind that while observational studies can show an association, they cannot prove cause and effect.
Also, even with randomized controlled trials, there are several limitations when it comes to nutrition research studies, including difficulties with accurately measuring food intake.
Researchers often rely on participants recalling what they have eaten in previous days, weeks, or months, but no one’s memory is perfect.
The research into whether dietary interventions can help treat mental health problems is relatively new and still quite limited.
The SMILES trial was one of the first randomized controlled trials to examine the role of diet in the treatment of depression.
Over 12 weeks, 67 individuals with moderate or severe depression received either dietary counseling or social support in addition to their current treatment.
The dietary intervention was similar to a Mediterranean diet, in that it emphasized vegetables, fruits, whole grains, oily fish, extra virgin olive oil, legumes, and raw nuts. It also allowed for moderate amounts of red meat and dairy.
At the end of the study, those in the diet group had significantly greater improvements in depression symptoms. These improvements remained significant even when the scientists accounted for confounding variables, including body mass index (BMI), physical activity, and smoking.
Furthermore, only 8% of individuals in the control group achieved remission, compared with 32% of those in the diet group.
Although these results seem promising, the SMILES study was a small, short-term study. As a result, larger, longer term studies are necessary to apply its findings to a larger population.
Replicating the findings is important because not all research agrees with them. For instance, in a study that recruited 1,025 adults with overweight or obesity and at least mild depressive symptoms, researchers investigated the impact of both a multinutrient supplement and food-related behavioral activation on mental health outcomes.
The scientists found no significant difference in depressive episodes compared with a placebo after 12 months.
In the same year, though, a meta-analysis of 16 randomized controlled studies did find that dietary interventions significantly reduced symptoms of depression, but not those of anxiety.
It is, therefore, difficult to draw solid conclusions from the existing body of research, particularly as the type of dietary intervention under investigation has varied greatly among studies.
Overall, more research is needed on the topic of specific dietary patterns and the treatment of mental health conditions. In particular, there is a need for a more standardized definition of a healthful diet, as well as for larger, long-term studies.
In addition to dietary patterns, scientists are interested in the potential effects that individual nutrients in the form of dietary supplements might have on mental health.
Scientists have found links between low levels of certain nutrients — such as folate, magnesium, iron, zinc, and vitamins B6, B12, and D — and worsening mood, feelings of anxiety, and risk of depression.
However, there is inconclusive evidence on whether consuming extra amounts of these nutrients in supplement form offers further benefits for mental health.
For instance, if someone is deficient in magnesium, for example, taking a magnesium supplement might help improve symptoms. However, if someone is getting adequate amounts of magnesium in their diet, it is unclear whether taking a supplement will provide any benefits.
Omega-3 fatty acids are essential fats that play a key role in brain development and cell signaling. An article in Frontiers in Physiology discusses how they reduce levels of inflammation.
Due to their anti-inflammatory effects and importance in brain health, scientists have investigated omega-3s for their potential effects on mental health.
While more research is still needed, in 2018 and 2019, reviews of randomized controlled trials found omega-3 supplements to be effective in the treatment of anxiety and depression in adults.
However, as with vitamin and mineral supplements, it remains unclear whether omega-3 supplementation can help improve mood in most individuals or whether it is primarily effective in those with the lowest intake of omega-3s.
Overall, when it comes to taking supplements for mental health, there is still a lot we do not know, including what the optimal doses are for various populations and the long-term safety and effectiveness.
Therefore, experts recommend acquiring the majority of these nutrients through a healthful and varied diet. Anyone who is concerned that they are unable to meet their nutrient needs through diet alone should speak with a doctor to discuss whether supplements may be helpful.
While there is a need for further research, observational studies suggest, overall, that there is a link between what people eat and their mental health. Why nutrition may have this effect is still unknown, though.
There are several theories on how diet may influence mood or the risk of conditions such as depression and anxiety.
Some scientists believe that the inflammatory effects of certain dietary patterns might help explain the relationship between diet and mental health.
For example, diets associated with benefits for mental health tend to be high in fruits, vegetables, whole grains, and healthful fats — all of which are foods rich in anti-inflammatory compounds.
A review of observational studies supports this theory, as diets high in antioxidants and anti-inflammatory foods were associated with a reduced risk of depression.
Still, the exact relationship between diet, inflammation, and alterations in mental health is not well-understood.
Another possible explanation is that diet may affect the bacteria in the gut, which people often refer to as the gut microbiome.
Ongoing research has found a strong link between gut health and brain function. For example, healthy bacteria in the gut produce approximately 90% of the neurotransmitter serotonin, which affects mood.
Furthermore, early research shows a potential link between a healthy gut microbiome and lower rates of depression.
As diet plays a major role in the health and diversity of the gut microbiome, this theory is a promising explanation for how what we eat may be affecting our mental well-being.
Finally, there is the possibility that diet plays a more indirect role in mental health.
It may be that individuals with healthful diets are more likely to engage in behaviors that are also linked with a reduced risk of mental health conditions, such as engaging in regular physical activity, practicing good sleep habits, and refraining from smoking.
It is important to keep in mind that many factors can influence both eating habits and mental health.
According to MentalHealth.gov, factors that can contribute to mental health conditions include biological factors, such as genetics, life experiences, and family history. Socioeconomic status can also affect mental health, as can access to food and overall diet quality.
Mental health can, in turn, affect eating habits. For example, it is not uncommon to turn to less healthful foods, such as sweets or highly processed snack foods, when feeling angry or upset.
Similarly, many antidepressants and anti-anxiety medications can increase appetite and cravings. In both of these situations, struggling with mental health can make adhering to a healthful diet more difficult.
Overall, while diet may be an important factor for mental health, it is important to remember that many other aspects of life can also contribute to mood.
The study of nutrition and how it affects mental health is ongoing.
And while more research is needed, current studies suggest that we may have some influence over our mental health through our food choices.
Still, we need to keep in mind that diet is just one piece of the much more complex topic that is mental health.
As a result, it is important for anyone who is experiencing depression or anxiety symptoms or has general concerns about their mental well-being to work with a trusted healthcare provider to develop a personalized treatment plan.