In a study from Macquarie University, scientists found people who eat a Western-style diet were more likely to have lower levels of kynurenic acid (KA) and report higher levels of depression than those eating diets rich in fresh fruit and vegetables.
KA is a small molecule important to a number of bodily functions.
The human body has a number of ways of producing important molecules and metabolites necessary to keep it functioning.
One of these important molecules is tryptophan—an essential amino acid that the body can’t make itself, that is found in foods like dairy products, poultry, bananas, oats, nuts, and seeds.
Our bodies break down tryptophan into metabolites that are used to regulate behavior, protect the brain, and control inflammation, which is linked to diseases including some cancers, heart disease, stroke, and dementia.
When tryptophan is broken down, it can produce either serotonin and melatonin—important for our mood and sleep—or it can be processed by the kynurenine pathway, which creates KA and other important metabolites linked to neurodegenerative diseases such as Alzheimer’s disease.
In the study, the team examined 169 adults aged 17 to 35. They tested participants’ urine for several biological markers, including KA and inflammation, and compared them with how healthy their diet was and the severity of depression symptoms.
They found people from the group eating an unhealthy diet had lower levels of KA and more severe symptoms of depression. This indicates that KA may help to protect us against depression.
This is the first time anyone has been able to show that a Western-style diet has an effect on the way that tryptophan is metabolized in otherwise healthy young people.
The study also shows that urine analysis may be a useful alternative to blood tests in collecting valuable biological information on the way our bodies process tryptophan.
This can be a big advantage in that it’s not only simpler—it’s less invasive, which is important for vulnerable people such as children and older adults.
The team says there is a clear relationship between an increased risk of depression and eating an unhealthy diet that is high in fat, sugar, and processed foods, giving us all the incentive to eat more fresh vegetables and fruit.
As with most metabolites, the level of KA in the body is important. Too little is associated with depression, but too much has been linked to schizophrenia.
If you care about mental health, please read studies about the key to depression recovery, and Omega-3 fatty acids could protect memory in healthy older people.
For more information about health, please see recent studies about medications for depression, and results showing these antioxidants could help reduce dementia risk.
The study was conducted by Dr. Edwin Lim et al and published in the journal Frontiers in Nutrition.
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