After taking into account sociodemographic, lifestyle and health-related behavioural characteristics, the researchers found that, during the experiment, people who consumed large amounts of highly processed foods were 23% more likely to experience elevated psychological distress.

Highly processed foods are high in carbohydrates and saturated fat and low in protein and fibre. They are also often low in micronutrients such as vitamin B12, vitamin D, vitamin E, niacin, pyridoxine, copper, iron, phosphorus, magnesium, selenium and zinc. These factors can have a significant impact on our mental health.

The authors are correct in stating that some highly processed foods are high in fat and low in micronutrients. For example, we know that vitamin D, B vitamins and amino acids are essential for optimal mental health and help prevent depression. This happens through a variety of mechanisms, such as reduced inflammation, less oxidative damage, improved gut microflora, etc., emphasises Dr Eamon Laird, a researcher at Trinity College Dublin not associated with the study.

One of the study's authors, Dr Melissa Lane, notes that eating unhealthy foods has a dangerous effect on us and may be more dangerous than we may think:

'Even after accounting for factors such as smoking, lower education, income or physical activity that are associated with poor health outcomes, this study shows that higher consumption of ultra-processed foods is associated with a higher risk of depression.