High energy, less nutritious foods are easily available and popular. In affluent countries, many people are overfed and undernourished. They don’t eat enough brain-essential nutrients, including B-vitamins, zinc and magnesium.
The human brain works at a very high metabolic rate. It uses a large amount of the total energy and nutrient intake. It relies on amino acids, fats, vitamins and minerals. A number of vitamins and minerals are co-factors in the synthesis of neurotransmitters - dopamine, serotonin and GABA.
Diet impacts the immune system and antioxidant defence system – which are implicated in mental disorders. Neurotrophic factors contribute to neuronal plasticity and repair mechanisms - and are also affected by nutrition.
Food has an emotional link. When rating healthy food, the left dorsolateral prefrontal cortex is activated - cognitive control is involved with making the choice that has a long-term view. The amygdala - a brain region associated with reward - is less activated.
On the other hand, rating unhealthy food causes higher activity in the right amygdala. Food choice is driven by neural signalling associated with reward.
Stress affects self-control. As shown by MRI, it enhances the impact of immediately rewarding attributes and reduces the efficacy of regions that promote long-term goal behaviours.
High intake of fast foods and processed pastries increases the risk of depression. Eating fish, vegetables, olive oil and cereal is associated with less severe depressive symptoms. Folate and omega-3 essential fatty acids play a role.
A Mediterranean diet - fruits, vegetables, nuts, legumes and fish - is associated with reduced inflammatory markers and may be protective against developing depression. This diet also increases plasma antioxidant levels and decreases oxidative stress.
The microbiome influences anxiety and depression. Changing the gut microbiota with specific probiotics or antibiotics can affect depression.
Early in life, gut microbiota are involved in programming the hypothalamic-pituitary-adrenal axis - which plays a role in reactivity to stress throughout life. Interestingly, stress in the womb and in early life impacts the microbial composition of the gut in infants. This may increase vulnerability to mental disorders in children.
Stress increases intestinal permeability - the leaky gut. Bacteria can enter the bloodstream and directly access immune cells and neuronal cells of the enteric nervous system. This may be how the microbiome influences the central nervous system.
Food sovereignty is the right to eat healthy and culturally appropriate food through sustainable and ecologically sensitive methods. It is the right to define food choices and agricultural systems.
Through the principle of healthy food, health - and mental health - may be part of this definition. But the actual evidence to support the idea that increasing food sovereignty improves human health is weak. More research is urgently needed.
About a quarter of young adults suffer from sleep problems. This includes sleep misperception and, to a lesser extent, severe insomnia. Sleep misperception includes problems with falling and staying asleep, and waking early. Insomnia may also involve anxiety in the night and nightmares.
The onset of most major psychiatric disorders is characterised by sleep disruption. Less sleep may be a risk factor for the onset of psychological distress. There are sleep ‘signatures’. In schizophrenia - reduced slow wave sleep. In depression - shortened rapid eye movement (REM) latency and increased REM density.
Exercise can reduce the risk of depression, and an active lifestyle can reduce depressive symptoms. Exercise is followed by an increase in anti-inflammatory cytokines and an up-regulation of antioxidant enzymes.
A study was described in which female adolescents with mild-to-moderate depression had improved depressive symptoms after 8 weeks on an exercise programme. Reduction in 24 hour cortisol levels was also seen.