The effects of junk food on our mental health


My research into gut health (see blog posted in September), prompted me to delve a little deeper into the effects that our increasing consumption of ready-meals, takeaways and ‘junk food’ is having on our mental well-being. Most of us are aware of the increased risk to our physical health of a high-fat/high sugar diet; western media regularly reports on the rise in obesity, heart disease and type 2 diabetes….but the effects on our brain and our mental health are not so well known.

Does our food affect our mood?

Depression can be triggered by many things, including traumatic events and extremely difficult circumstances……but evidence suggests that chronic depression can be due to an inadequate diet.


Depression is a whole-body disorder

Researchers now believe that depression is not just a brain disorder, but rather a whole-body disorder, with inflammation being an important risk factor. This inflammation is the result of many environmental stressors common in our lives: poor diet, lack of exercise, smoking, overweight and obesity, lack of sleep, lack of vitamin D, as well as stress. Many of these factors influence the bacteria and other microorganisms that live in our gut, (also referred to as our ‘microbiome’), which are important to almost every aspect of our health including our brain function. The key gut-brain axis is an increasing focus of attention, given the recent understanding regarding the importance of the gut microbiota in influencing brain and behaviour, and the recognition that diet is a key modulator of gut microbiota and gut health.

Junk food is linked to depression

Researchers in Britain followed 3,000 middle-aged office workers over a period of five years monitoring their diets and reported levels of depression. Those who ate a diet high in junk food including processed meat, chocolate, sweet desserts, fried food, refined cereals, and high-fat dairy products were more likely to report depression than those who ate a diet rich in fruits, vegetables, and legumes. See the full report here.

In a larger European study of over 12,000 volunteers whose diets and lifestyles were followed for six years, researchers found that participants whose diets were high in trans-fats (present in commercially baked goods and fast-food) were 48% more likely to develop depression than those who did not consume trans-fats. See the full report here.

Another study looked at the association between diet quality and depression and anxiety in 5,731 adults. A traditional Norwegian diet was associated with reduced depression and anxiety, and a ‘western’ type diet with a higher intake of processed and unhealthy foods was associated with increased depression and anxiety. See the full report here.


Does diet effect our children’s mental health?

The relationship between diet and mental health is evident right at the start of life. A Norwegian study followed 20,000 women during their pregnancies, and for the first five years of their children’s lives. The research found that children of mothers who ate an unhealthier diet during pregnancy displayed a higher level of emotional and behavioural disorders, as did children who consumed unhealthy diets during their first years of life. This suggests mothers’ diets during pregnancy, and what their children eat in their first years of life, are both important in influencing the risk for mental health problems as they grow. See the full report here.

As children become adolescents, new freedoms and increased disposable income give them more control over what snacks and drinks to buy, and the ready availability and cultural acceptance of ‘junk food’ makes it a normal part of daily life for many teenagers. An Australian study examined over 7,000 adolescents for healthy and unhealthy diets and the incidence of depression, and found an association between diet quality and depression that exists over and above the influence of socioeconomic, family, and other potentially confounding factors. In other words, teenagers with poor diets are more likely to be depressed no matter if they are rich or poor, what kind of family they have, or where they live. See the full report here. Another study carried out amongst adolescents in China, produced similar results. See the full report here.

Can a change of diet improve our mental health?

A trial carried out in Australia and published in January 2017, was the first intervention study to examine whether a change to a healthy diet can improve depression. They recruited adults with major depressive disorder and randomly assigned them to receive either social support (which is known to be helpful for people with depression), or support from a clinical dietitian, over a three-month period. The dietary group received information and assistance to improve the quality of their current diets. The focus was on increasing the consumption of vegetables, fruits, wholegrains, legumes, olive oil and nuts, while reducing their consumption of unhealthy ‘extra’ foods, such as sweets, refined cereals, fried food, fast food, processed meats and sugary drinks.

The results of the study showed that participants in the dietary intervention group had a much greater reduction in their depressive symptoms over the three months, compared to those in the social support group. By the end of the trial, 32% of those in the dietary support group, compared to 8% of those in the social support group, met criteria for remission of major depression. These results were not explained by changes in physical activity or body weight, but were closely related to the extent of dietary change, and those who adhered more closely to the dietary programme experienced the greatest benefit to their depression symptoms.


The ‘western’ diet and its attendant obesity, disease, and mental illness is spreading throughout the world. The seduction of processed food is sweeping across the planet from industrialized nations to previously secluded tropical paradises. As populations forego the traditional, wholesome diets that have kept their rates of physical and mental illness far below those of the western world, we can expect to see that change. And as diet related illnesses increase, so does the amount of money being invested in pharmaceutical companies to manufacture products that will reduce and reverse the effects of these nutritional imbalances. The kind of nutritional imbalance that predictably occurs when we stop eating whole, natural, real food and substitute it with packaged, artificial food that is nutritionally deficient and full of sugar, trans-fat, artificial colours and flavours, preservatives, and other substances that are toxic to our bodies.

Thank you for reading this blog post. If you have any thoughts to share, or ideas for future posts, please do let me know. I would love to hear from you.

Thomas HallComment