Fast food and the fast route to depression

We’ve all heard the phrase ‘you are what you eat’ and the majority of us are familiar with the fact that so-called ‘junk food’ can have a major influence on our health, both short and long term. According to a recent study from Spain, this goes further than influencing susceptibility to physical ill health; diet can influence psychological health.

Researchers, recruiting 8964 individuals who were free of depression at enrolment, reported 493 cases of depression after median follow-up of 6·2 years.  Participants were classified as incident cases of depression if they reported a doctor’s diagnosis of depression or the use of antidepressant medication in at least one of the follow-up questionnaires.  Food frequency questionnaires were used to establish regular dietary habits and the consumption of fast food (hamburgers, sausages, pizza) and processed pastries (muffins, doughnuts, croissants) assessed at baseline.    A higher risk of depression was associated with those participants consuming the highest amounts of fast food and commercial baked goods compared to those with the lowest level of fast food consumption.  Importantly, the results did not change after adjustment for the consumption of other food items that could be considered to have a protective effect on depression risk.

Whilst the introduction of food processing and refining has led to cheaper, highly available foods such as those reported in this study, such foods are typically of poor nutritional value. Inrecent years, there have been great changes in the way we see food and how we eat. The substantial rise in availability and consumption of highly processed ‘convenience’ and ‘junk’ food is seen as an appropriate response to our lives: fast living requires fast, instant food.     Indeed, the 24/7 culture in which many of us now juggle a busy work life with family, personal interests and social commitments, often necessitates convenience eating, with little awareness of its nutritional content or the impact this might have on our health.  Coupled with the fact that we tend to over-eat the wrong types of food when we’re feeling stressed, depressed or short of time, the diets of many, particularly in the West, are suffering – a factor in the deterioration of our mental and physical health.   What is apparent is that, while many people are increasingly aware of the role of healthy eating in protecting against conditions such as cardiovascular disease or diabetes, the link between diet and its role in maintaining mental well-being is not so well known.  The long-term effects, however, are routinely and consistently exposed as having a significant negative effect on our health and our mood.

The message is getting louder, but still has to be heard by many more, that there is a need to eat well to avoid (or at least minimise the risk of) physical and mental ill health. Food types such as those defined in this recent study are often high in saturated fat and/or refined sugar and low in essential vitamins and minerals.  Sugar, for example, is a major cause of fluctuating mood because when you eat something sugary, your blood sugar level rises sharply, followed an hour or so later by a ‘sugar low’, as the amount of sugar in your blood decreases. This has a negative effect on both mood and energy levels, leading to poor concentration, anxiety and irritability.  Coupled with this, excessive consumption of saturated fat and trans fat can change the structure of our cell membranes, causing them to become rigid and less susceptible to the actions of the mood-enhancing neurotransmitter serotonin.

Depression is a complex condition and the causes of depression are multiple, affecting no two individuals in the same way.  Diet is increasingly recognised by science to be one of the many factors that can contribute to the onset of depression.  Eliminating all sources of processed food may be a struggle for many people, but the clear message is that restricting intake of energy-dense, nutrient-free food can act as a way of reducing our risk of developing not only ill health in the future, but also as a way to reduce our chances of developing depression as we get older.

Sánchez-Villegas AToledo Ede Irala JRuiz-Canela MPla-Vidal JMartínez-González MA.  Fast-food and commercial baked goods consumption and the risk of depression. Public Health Nutr. 2011 Aug 11:1-9. [Epub ahead of print]

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