Nutrition and mental health

While diet plays an important role in physical health, there is a growing body of research focusing on its role in mental health. In a context where the pandemic has caused a considerable increase in anxiety and depression disorders, in addition to the time of year when seasonal depression is rife, putting sun on your plate is more relevant than ever!


  • One in five adults would have had symptoms consistent with generalized anxiety disorder or major depression in the two weeks preceding the survey.
  • In urban areas, especially in Montreal, one in four adults has the same characteristics.

1 Web survey conducted by the firm Léger among 6,261 adults from September 4 to 14, 2020.

Food and the mood

Several factors affect our mental health, including genetic, biological and environmental factors. For Dr. Howard Steiger, head of the eating disorder continuum at the Douglas Mental Health University Institute, incorporating precursors of certain mood-regulating neurotransmitters into our diet could be a game-changer. Tryptophan, an amino acid precursor of serotonin, the neurotransmitter of well-being, would have a role to play in particular. “It is well established that a diet rich in tryptophan improves mood and our social behaviors,” says Dr. Steiger. Foods rich in tryptophan include eggs, fish, poultry and milk.

Also professor of psychiatry at McGill University, Howard Steiger is interested in epigenetics, the capacity of certain micronutrients to alter the expression of our genes. A specialist in eating disorders, he has notably demonstrated that malnutrition linked to anorexia affects the expression of genes that regulate brain functions, disrupting the mechanisms responsible for regulating mood and social behavior.

Sugar and depression

Consuming refined sugars increases the risk of obesity and diabetes. Sugar would also affect psychological health. Several epidemiological studies have linked sugar consumption to an increased risk of depression. In one (Whitehall Study), men who consumed more than 67 g of sugar per day (more than 16 teaspoons of sugar) were 23% more likely to develop depression compared to those who had it. consumed less than 40 g (less than 10 tsp). If this study does not confirm a causal relationship, it raises interesting hypotheses. In particular, excessive sugar consumption would affect dopamine, the neurotransmitter associated with the reward circuit, and cause cellular inflammation, two factors linked to mental health. Other studies have documented the negative impact of high sugar and saturated fat intake on depressive symptoms.

Cravings and stress

Cravings for foods high in carbohydrates have been observed in both animal models and humans under stress. The consumption of foods rich in carbohydrates (cereal products, desserts, etc.) increases the synthesis of serotonin (by increasing the uptake by the brain of its precursor, tryptophan), which has calming properties. The desire to eat foods high in carbohydrates and sugars under stress could be explained by this effect on serotonin. Several surveys carried out since last March have also shown that many Quebecers snack more and eat sweeter since confinement. The stress associated with the health crisis therefore seems to influence our eating habits.

Microbiota and mood

All the foods we eat affect the composition of our gut microbiota. Our gut microbiota and our brain constantly interact through the gut-brain axis. Depending on the type of food ingested, intestinal microorganisms produce metabolites that affect our mental health. “In people with mental illness, depression, eating disorders and post-traumatic stress, there is an alteration in the gut microbiota with respect to the composition, diversity and number of bacteria,” says Dr Steiger.

Science is evolving rapidly and several researchers are interested in the influence of food on the microbiota. Several nutrition experts recommend a diet rich in dietary fiber, probiotics and prebiotics to favorably modulate the composition of our flora. Mediterranean and vegetarian diets are also the subject of research which tends to demonstrate the favorable effect on the diversity of flora.

Processed and ultra-processed foods would negatively affect our microbiota, creating inflammatory metabolites that could increase the risk of depression.

Eat well for his health mental

Even though the science is still young, we now know that food has the power to affect our mental health. While a diet high in saturated fat and sugar is bad for physical health, it is also bad for mental health. Population studies have reported that adherence to a diet rich in fruits, vegetables, nuts, fish and legumes is associated with a reduced risk of depression.

Dr Steiger also stresses the importance of variety on our plate. A greater diversity of microorganisms within our microbiota is definitely associated with better mental and physical health. People with obesity, eating disorders and other mental disorders often lack bacterial diversity in their gut flora. Despite the encouraging data, the emeritus researcher urges us to be cautious, the effects of food on morale remain modest and the coming years will confirm the results and above all clarify the recommendations in terms of clinical intervention aimed at preventing depression or even at alleviate its symptoms.

-Thanks to Asma Hassan Abidalameer, nutrition intern, for her precious collaboration

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