Nutrition and mental health

What we eat has a big impact in all aspects of our well-being. The relationship between nutrition and mental health has been a topic of interest for quite some time and is especially relevant in uncertain times.

Healthy vs unhealthy diets

Higher intakes of fruits, vegetables, fish and whole grains seem to reduce the risk of depression (1, 2). On the flip side, unhealthy diets are associated with increased mental health problems. This negative effect seems to be true in diverse populations, i.e. across different age ranges, genders and ethnicities (1).

Dietary patterns

Some dietary patterns such as the Mediterranean diet, a traditional Japanese diet and a typical Tuscan diet have been linked with a lower risk of depression. Note that besides the reliance on fruits and vegetables, these dietary patterns also have a low to moderate intake of meat and a low intake of processed and sugary foods (2).

A variation of the Mediterranean diet which also included moderate amounts of red meat and dairy, was shown in a trial to improve mood (1).

“Antidepressant” foods

Under the premise that dietary patterns are difficult to follow by people who don’t belong to a particular culture, a group of Canadian and American scientists decided to come up with a list of foods based on their antidepressant potential. The authors compiled and weighed a list of nutrients inversely associated with depression (folate, iron, omega-3 fatty acids, magnesium, potassium, selenium, thiamine, zinc and vitamins A, B6, B12 and C). They then built a list of the top whole foods with higher content of those nutrients (3).

The foods with highest content in those nutrients included oysters, organ meats, some seafood, fish and goat, dark leafy greens, fresh herbs, capsicum cruciferous vegetables, pumpkin and some citrus. The full list can be found in the paper cited below (3). Data was gathered by 100g of raw food, which represents a couple of nuances in my opinion. First, many nutrients are lost during food preparation (and the authors mentioned this), therefore they should have done the analysis based on the form (raw or cooked) that is most commonly used. Second, normal portions sizes may be much larger or much smaller than 100g (e.g. fish roe vs fish fillet, broccoli vs parsley). Moreover, the list contains some foods that might be obscure to many people such as smelt, wolffish, pollock, snail or whelk, spot fish and acerola. Finally, I agree with the authors when they say that focusing on nutrient dense foods automatically reduces energy intake, which may help with conditions other than depression.

Supplements and mental health

There is plenty of evidence that omega-3 supplements, especially those containing more EPA than DHA have a positive impact on mood disorders (1).

Other supplements that have been trialled and may be used alongside other therapies for mood disorders are folic acid, S-adenosyl-methionine (SAMe), methylfoate and vitamin D (1).

Although some reviews have found limited support for zinc supplements (1), they have been found to potentiate the effects of antidepressant drugs (4).

Magnesium deficiency is associated with depression, although there are a number of confounding factors including the status of other nutrients such as vitamin D and calcium (4).

Gut microbiome

It is widely known that there is a gut-brain axis through which our gut microbiome communicates with our brain, affecting behaviour. Our diet has a direct effect in the composition of our microbiome. Again, fruits and vegetables along with complex carbohydrates seem to elicit positive effects on our gut bacteria, while processed foods, high fat and high refined sugar diets seem to have a negative effect (at least in animals). Probiotics and fermented foods may also help improve gut health (1).

Fecal microbiota transplants could potentially be used depression (2).

Summary and recommendations

What we know as a healthy diet (plenty of vegetables, fruit, whole grains, nuts, seeds, fish and healthy fats) seems to be beneficial for mental health.

While there are multiple dietary patterns that have been shown to reduce the risk of depression, it is important to remember that when we eat, we not only feed ourselves but also our gut bacteria. The composition of our microbiome is likely to be generally suited for the culture we come from. Therefore, adopting a healthy traditional diet in line with our genetic heritage would make more sense than blindly eating regional diet X just because it seems to be helpful for mental health.

Although some supplements have been found to be useful as adjuvant treatments for depression, it is best to aim for nutrient sufficiency through diet before considering supplementation. As always, please ask an Accredited Practising Dietitian before taking supplements, especially if you have a diagnosed medical condition.

Finally, a healthy diet is not a guarantee for optimal mental health because there are many other factors involved. Other lifestyle factors such as exercise, stress and sleep need to be addressed as well, sometimes alongside medical intervention.

References

1. Jacka FN. Nutritional Psychiatry: Where to Next? EBioMedicine. 2017;17:24-9.
2. Huang Q, Liu H, Suzuki K, Ma S, Liu C. Linking What We Eat to Our Mood: A Review of Diet, Dietary Antioxidants, and Depression. Antioxidants (Basel, Switzerland). 2019;8(9).
3. LaChance LR, Ramsey D. Antidepressant foods: An evidence-based nutrient profiling system for depression. World journal of psychiatry. 2018;8(3):97-104.
4. Wang J, Um P, Dickerman BA, Liu J. Zinc, Magnesium, Selenium and Depression: A Review of the Evidence, Potential Mechanisms and Implications. Nutrients. 2018;10(5).

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