Depression and diet: how are they related?

What is depression? 

Depression is a common mental disorder affecting more than 300 million people worldwide. It is estimated that nearly one in six people living in the UK has suffered or will suffer from depression in their lifetime.

The symptoms of this disease have a significant impact on patients' daily life as they disrupt their normal day-to-day activities.

There are several types of depression, which are defined in the DSM-IV (Diagnostic and Stastitical Manual of Mental Discorders), a basic medical textbook for the diagnosis of mental disorders.

There are also several risk factors for and causes of depression: biological, psychological, sociological, environmental and the ones related to the patient's personal history.

Once a diagnosis has been made by a doctor or a psychiatrist, 3 approaches to treating depression can be considered:

• Psychotherapy,
  
• Drug treatments,
  
• Light therapy.
  

Alternative methods have proven to be effective, such as exercise, relaxation techniques, acupuncture and homeopathy, among others. In the case of severe depression, brain stimulation in a hospital setting can be considered, as well as transcranial magnetic stimulation.

Many avenues of research are being explored to find ways to combat depression and improve treatment, including the existence of a link between depression and the patient's diet.

What is the link between depression and diet? 

The impact of diet on our physical health is well known. A healthy and balanced diet promotes well-being and improves quality of life, especially of those who suffer from various health conditions.

This is why numerous public health campaigns all over the world encourage people to pay special attention to the food they eat.

Increasingly, a lot of research is being carried out that highlights the link between mental health and diet through our gut microbiota, for example. The aim of this research is to better understand the pathophysiology of depression and other mental disorders and to develop new treatments.

New disciplines, not yet recognised, are emerging, such as psychonutrition, nutritional psychiatry and neuronutrition. Their aim is to optimise the work of our brain and our mental functions by ensuring that the brain's essential needs are met.

In one study, it was shown that a diet rich in processed, fried, sugar-rich products, etc., is associated with an increase in depressive symptoms. This would be due to the chronic inflammation caused by this type of food.

In another study, it was shown that adopting a healthier diet, consisting mainly of fruit, vegetables, fish and cereals, was associated with a 33% reduction in the risk of depression.

More precisely, researchers have discovered how a change in the intestinal microbiota, due to diet or chronic stress for example, can be at the origin of a depressive episode by causing a collapse of lipid metabolites (small molecules resulting from metabolism) in the blood and the brain. These metabolites normally bind to receptors, the same as those activated by CBD or THC (cannabinoid molecules), and stimulate the endocannabinoid system (ECS). When endocannabinoids are no longer present in the hippocampus, the area of the brain involved in the formation of our memories and emotions, a depressive episode may occur. In this example, the use of certain bacteria could be an effective lever to restore one's microbiota and reduce the symptoms of depression.

What kinds of food can help reduce the symptoms of depression? 

Following certain lifestyle and diet recommendations may improve the patient's quality of life and thus their mental well-being. These recommendations include exercising regularly, sleeping well, limiting alcohol consumption, stopping smoking, maintaining family and social ties, taking up different activities that bring you pleasure and eating a healthy and balanced diet, among others.

Food provides energy for our bodies to function correctly, grow, strengthen and change.

Incorrect nutritional intake, such as foods that are too fatty and sugary or low in calcium, may contribute to symptoms of mental disorders such as depression, while other foods may help to combat it.

One should not draw premature conclusions, as there is no specific diet for the treatment of depression. However, the question arises as to the impact of our diet on our mood with a hedonistic approach which would like an individual's happiness to also reside in dietary behaviours favourable to their well-being.

Among the various diets that exist, the Mediterranean diet is said to contribute to the prevention of depression. It is rich in:

• Seasonal fruit and vegetables,
  
• Wholemeal pasta, rice and bread,
  
• Dried vegetables,
  
• Oily fish (sardines, mackerel, herring, salmon, etc.),
  
• Olive oil,
  
• Dried fruit (walnuts, hazelnuts, almonds, pistachios, etc.).
  

This diet contains vitamins, antioxidants, fibre and Omega-3 which all have a positive effect on our mental health.

B vitamins play an important role in the formation of neurotransmitters such as dopamine, serotonin and noradrenaline, which regulate mood and fatigue.

Vitamin D, in combination with sunlight, can cause winter depression when it is not sufficiently synthesised. Vitamin D deficiency is also thought to be linked to postpartum depression.

It is also advisable to eat enough protein, which is found in red meat, white meat, fish, beans and lentils. The amino acids in protein, especially tryptophan, are used to make serotonin, which is important for mood management.

In terms of foods to limit so as not to aggravate the symptoms of depression, there are in particular :

• Alcohol and psychoactive substances, which can trigger or worsen the symptoms of depression,
  
• Industrial foods, which cause inflammation and activate the immune system in an abnormal way, with consequences for the nervous system and therefore for neurotransmitters,
  
• Sugary foods, an excessive intake of sugar may increase the risk of depression.
  
  
  

Further clinical trials and medical research are needed to assess the effectiveness of diet in reducing the risk and severity of depressive disorders.

Today, diet modification is not a sufficient approach to treating depression, but depending on the individual, it can help. Seeing a mental health professional and asking for advice remains the first option.

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