Heredity plays an important role in human mental function. The scientific evidence of a genetic role in mental diseases such as schizophrenia, bipolar disorders, and others tells us a strong link between psychiatric disorders and specific genetic markers. Nonetheless, hereditary studies also tell us about the environmental influence on gene expression. We can also make a case on certain psychological factors that are important environmental components, which interact with genes or gene products to promote the expression of a phenotype. Here we can have a detailed overview of how nutrition and physical activities play a significant role in mental health.
The heritability for psychiatric disorders suggests that there is a significant environmental component in the pathogenesis of psychiatric disorders. For nutrition which powerfully impacts physical health and disease the mechanisms of the gene-environment interaction are under investigation.
Psychiatric Disorders & Genetic Regulation and Environmental Influences
The human being is a complex creature, largely because of the cognitive functionality and complexity associated with the human psyche. Hereditary mechanisms of human mental function and dysfunction are extremely complex because of the interaction of multiple genes. Our genes instruct the development of the central nervous system (CNS), but our environmental factors promote or in the case of hypoxia, infection or malnutrition may disturb the maturational processes. In the case of psychotic diseases such as schizophrenia, even if 100% of genes are shared as would be the case for an individual with two schizophrenic parents, the risk of developing the condition is estimated to be no more than 46%, leaving a substantial portion to environmental factors.
A genetic precondition is not only the factor that determines a person’s mental disorder. There is strong evidence that the maternal environment influences the fetal developmental process. There are many scientific observations that growth restriction of fetal life is linked with an abnormal level of increased adrenocortical hormones as well as adrenomedullary activity. Moreover, there is a piece of evidence that fetal life abnormalities are associated with a high level of autoantibodies to thyroid peroxidase (TPOAb) and thyroglobulin (TgSAb) are significant in view of the presence of similar endocrine abnormalities in major depressive disorders.
Historical Evidence of Schizophrenia Linked with Malnutrition
Epidemiological studies of psychiatric disorders have linked severe malnutrition during the first trimester to the risk of schizophrenia by analyzing the incidence of schizophrenia in birth cohorts born between January-February 1944 and November–December 1946 in Holland during the German occupation. Those conceived during the height of the Dutch famine and exposed to very low food rations during the first trimester (from February to April 1945) had an excess of neural tube defects and double the relative risk for schizophrenia. As noted previously, suggested that the epsilon-4 genotype of the APOE gene may be associated with the risk of malnutrition for schizophrenia. First-trimester exposure to severe malnutrition during the Dutch hunger winter has also been reported to double the risk of schizoid personality disorders, schizophrenia spectrum disorders, and antisocial personality disorder. Malnutrition during the second trimester appears to double the risk for affective disorders in adulthood.
Interaction between Nutrition, Growth, and Development
It has been studied that fish oil supplements given from week 30 of the pregnancy extended the pregnancy duration on average 4 days compared to women receiving olive oil supplements. Seafood has been effective in healthy conceive whereas low seafood diet is associated with premature delivery. Moreover, the study shows that higher maternal DHA levels are associated with more mature infant sleep and wake states in newborns.
Maternal supplementation with cod liver oil (total 1.2 g DHA 0.8 g EPA) versus corn oil (4.7 g linoleic acid (LA) and 0.09 g- linolenic acid (ALA) from week 18 of pregnancy until 3 months after delivery increased children’s mental processing composite score significantly at 4 years of age. Another study found similar visual, cognitive, and language scores in breastfed and DHA- and DHA AA-enriched formula-fed children at 39 months.
Diet for ADHD and Autism
There are strong evidence of correlation between diet and ADHD. For example, a meta-analysis across 20 studies that involved 794 participants found a small effect size of removal of food additives based on parent reports, and if there is more large elimination diets that shows that an improvement in several randomized clinical trials.
- Two independent meta-analyses were conducted that show effect sizes of 0.29 to 0.51 across 6 controlled trials and concluded an improvement over one-third of the children with ADHD.(>40% symptom reduction).
- Moreover, fatty acid supplements have also been linked with a small but reliable decrease of ADHD symptoms with effective sizes varying from 0.18 to 0.31.
- Supplementation with micronutrients results in a reduction of aggression and better emotion regulation in children with ADHD.
- Meta-analyses suggested that a diet high in refined sugar and saturated fat increases the risk of ADHD or hyperactivity in children.
Diet, Mental Health and Cognition in Adulthood
Diet plays an important factor in adult life. It has been studied that a high-quality diet is highly correlated with a reduced risk of cognitive decline. Moreover, a diet supplemented with antioxidant polyphenols in adult life has been associated with improved cognitive abilities.
In an older population, a controlled study shows that a Mediterranean diet supplemented with olive oil and nuts significantly improved cognitive function. Scientists are working on the role of nutritional interventions to combat cognitive decline, especially in aging under conditions of heightened stress and anxiety.
Moreover, some rodent model studies showed that the consumption of a high-fat diet can have anti-depressant and anxiolytic effects. There is another side of the story that tells us that the high-fat and high sugar diet is associated with cognitive impairments, particularly memory impairments and increased anxiety-like behavior.
Diet has a significant factor in obesity and obesity is associated with hippocampal dysfunction and short-term memory loss in humans.
What we eat, our physiological and mental well-being is highly dependent on that. The scientific consensus on this fact is overwhelming. Diet and nutrition are not only essential for human physiology and body composition but also have important effects on mental health. While the exact determinants of mental health are complex, the scientific evidence indicates a strong correlation between a poor diet and the exacerbation of mood disorders, including anxiety and depression. Also, people with a poor diet are likely to suffer from neuropsychiatric conditions.
Nutrition and Fitness: Mental Health, Aging, and the Implementation of a Healthy Diet and Physical Activity Lifestyle – Editor, A.P Simopoulos