A large study has found that eating ultra-processed foods, such as fast food, significantly increases the risk of depression.
Health experts have explained that these foods have long been linked to complications from heart disease, cancer, diabetes and Alzheimer's disease.
Now, researchers at the Tehran University of Medical Sciences in Iran have concluded that eating fast food regularly increases the risk of depression by 15%.
The study, which used data from clinical trials around the world as well as studies that included 160,000 men and women, focused on looking for links between mental illness and malnutrition.
She explained that ultra-processed foods (UPFs) are often high in fat, salt and sugar, with a lack of vitamins and fibre.
The research team revealed that UPFs may cause inflammation in the brain, leading to mental health problems.
The Iranian study (the largest to date on the impact of diet on mental health) also indicated that these foods may reduce levels of a protein called brain-derived neurotrophic factor in the body, which is critical for healthy mental function.
However, some experts believe that ultra-processed foods may not necessarily lead to depression, arguing that people with depression are more likely to make poor food choices.
“When people are feeling down, they often don’t put in the effort to cook, so they turn to ready-made meals,” says Gunter Kunle, professor of nutrition and food science at the University of Reading. “We’ve known for a long time that there is a strong link between diet and mental health, but it’s hard to say definitively that a poor diet causes depression.”
It is noteworthy that the world's largest review conducted earlier this year found that UPFs increase the risk of harm to every part of the body when consumed in large quantities.
The review, published in the British Medical Journal, revealed that diets rich in UPF elements increase the risk of death from a heart attack or stroke by 50%.