Dietary nutrients are critical for brain structure and function, so they have a potentially profound impact on mental health. An increasingly robust body of research points to the detrimental effect of unhealthy diets and nutrient deficiencies, and to the protective value of healthy diets – along with select nutritional supplements as required – for maintaining and promoting mental health.
Research literature suggests dietary improvement and nutritional interventions may help reduce the risk, or even arrest the progression, of certain psychiatric disorders. Clinical studies support the use of certain nutrients, which influence a range of neurochemical activities beneficial for treating mental disorders, as medicinal supplements.
Evidence from clinical research supports the use of several nutritional medicines for certain psychiatric disorders: omega-3 fatty acids; N-acetyl cysteine (NAC); S-adenosyl methionine (SAMe); zinc; magnesium; vitamin D; and B vitamins (including folic acid). Other natural compounds such as amino acids, plant-based antioxidants and microbiotics (derived from fermented food or laboratory synthesis) are also known to influence brain health.
But while some evidence supports these natural compounds as having brain chemical-modulating effects, or having a role in treating certain mental disorders, we cannot currently name particular foods as being effective for the treatment of mental illness. The best nutritional advice at this point is to cultivate an unprocessed wholefood diet, with judicious prescriptive use of nutrients (if required) based on advice from a qualified health professional.
In the meanwhile, here are seven key nutrients that may positively influence brain health, and the foods they appear in.
Polyunsaturated fats (in particular omega-3 fatty acids) have a vital role in maintaining proper neuronal structure and function, as well as in modulating critical aspects of the inflammatory pathway in the body. Taking omega-3 supplements appears beneficial for addressing symptoms of depression, bipolar depression and post-traumatic stress disorder. And it may potentially help prevent psychosis.
Omega-3 fats can be found in nuts, seeds and oysters, although the highest amounts exist in oily fish such as sardines, salmon (especially King salmon), anchovies and mackerel. Due to higher levels of mercury, larger fish, such as mackerel, should be consumed in moderation.
2. B vitamins and folate
We need B vitamins for a range of cellular and metabolic processes, and they have a critical role in the production of a range of brain chemicals. Folate (B9) deficiency has been reported in depressed populations and among people who respond poorly to antidepressants.
Several studies have assessed the antidepressant effect of folic acid (the synthetic form of folate) with antidepressant medication. Some show positive results in enhancing either antidepressant response rates or the onset of response to these medications.
Folate is found in abundance in leafy green vegetables, legumes, whole grains, brewer’s yeast and nuts. Unprocessed meats, eggs, cheese, dairy, whole grains and nuts are, in general, richest in B vitamins. If you’re going to take supplements, it’s advisable to take B vitamins together as they have a synergistic effect.
3. Amino acids
Amino acids are the building blocks for creating proteins, from which brain circuitry and brain chemicals are formed. Some amino acids are precursors of mood-modulating chemicals; tryptophan, for instance, is needed to create serotonin. Another example is cysteine, a sulphur-based amino acid that can convert into glutathione – the body’s most powerful antioxidant.
When given as a supplement, an amino acid form known as N-acetyl cysteine (NAC) converts into glutathione in the body. We have evidence that it’s helpful in bipolar depression, schizophrenia, trichotillomania and other compulsive and addictive behaviours. Another amino acid-based nutrient known as S-adenosyl methionine (SAMe) has antidepressant qualities.
Amino acids are found in any source of protein, most notably meats, seafood, eggs, nuts and legumes.
Minerals, especially zinc, magnesium and iron, have important roles in neurological function.
Zinc is an abundant trace element, being involved in many brain chemistry reactions. It’s also a key element supporting proper immune function. Deficiency has been linked to increased depressive symptoms and there’s emerging evidence for zinc supplementation in improving depressed mood, primarily alongside antidepressants.
Magnesium is also involved in many brain chemistry reactions and deficiency has been linked to depressive and anxiety symptoms. Iron is involved in many neurological activities and deficiency is associated with anxiety and depressive symptoms as well as developmental problems. This is, in part, due to its role in transporting oxygen to the brain.
Zinc is abundant in lean meats, oysters, whole grains, pumpkin seeds and nuts, while magnesium is richest in nuts, legumes, whole grains, leafy greens and soy. Iron occurs in higher amounts in unprocessed meats and organ meats, such as liver, and in modest amounts in grains, nuts and leafy greens, such as spinach.
5. Vitamin D
Vitamin D is a fat-soluble compound that’s important as much for brain development as it is for bone development. Data suggests low maternal levels of vitamin D are implicated in schizophrenia risk, and deficiency is linked to increased depressive symptoms. But there’s little evidence to support the use of vitamin D supplements for preventing depression.
Vitamin D can be synthesised via sunlight: 15 minutes a day on the skin between 10am and 3pm during summer, although be sure to seek professional health advice regarding skin cancer concerns. Aside from sunlight, vitamin D can also be found in oily fish, UVB-exposed mushrooms and fortified milk.
6. Plant-based antioxidants
An increase in oxidative stress and damage to brain cells has been implicated in a range of mental disorders, including depression and dementia. Antioxidant compounds (such as “polyphenols”, which are found in fruits and certain herbs) may “mop up” free radicals that damage cells to provide a natural way to combat excessive oxidation.
Consuming natural antioxidant compounds through your diet is better than taking supplements of high doses of synthetic vitamin A, C or E, as the oxidative system is finely tuned and excess may actually be harmful.
Fruits and vegetables contain these antioxidant compounds in relative abundance, especially blackberries, blueberries, raspberries and goji berries; grapes; mangoes and mangosteen; onions; garlic; kale; as well as green and black tea; various herbal teas; and coffee.
Research shows a connection between the bacteria in our guts and brain health, which may affect mental health. When the composition of the gut microbiota is less than optimal, it can result in inflammatory responses that may negatively affect the nervous system and brain function.
A balanced microfloral environment is supported by a diet rich in the foods that nourish beneficial bacteria and reduce harmful microbial species, such as Helicobacter pylori. Beneficial microflora can be supported by eating fermented foods such as tempeh, sauerkraut, kefir and yoghurt, and also by pectin-rich foods such as fruit skin.
Diets high in sugary, fatty and processed foods are associated with depression and poor brain health. While nutrient supplementation can have a role in maintaining proper brain function and treating certain psychiatric disorders, nutrients should, in the first instance, be consumed as part of a balanced wholefood diet.
There is now enough research evidence to show the importance of nutrients for mental as well as physical well-being. A discussion about diet and nutrition should be the starting point in conversations about mental health, just as it is for physical health.
If you’re interested in participating in a clinical trial prescribing nutrients for treating depression (SE Queensland and Victoria only), visit nutrientsdepressionstudy.
Acknowledgement: Dr Drew Ramsey contributed to this article.