The Grapevine

Vegetarian Diet Benefits Include Reducing Depression Risk, Study Suggests

It is known that poor mental health can affect appetite in a harmful manner. But how much of an influence do poor eating habits have on our susceptibility to mental health problems? 

Researchers at the University College London, England reviewed several studies published in recent years to find out. Their review titled "Healthy dietary indices and risk of depressive outcomes: a systematic review and meta-analysis of observational studies" was published in Molecular Psychiatry on Sept. 26.

Dr. Camille Lasalle and her colleagues conducted the review by aggregating the results of 41 multi-country studies. The aim was to identify a potential link between the quality and type of diet a person followed and their risk of developing depression.

The findings seemed to shed light on "a clear pattern," according to the researchers. People who followed a more Mediterranean-like diet had a 33 percent lower risk of developing depression compared to those whose eating patterns least resembled a Mediterranean diet.

Inspired by the eating habits of countries bordering the Mediterranean Sea, this type of diet is not too different from a healthful vegetarian one, encouraging a high intake of fruits, vegetables, olive oil, nuts, and fish.

Thus, the findings suggest that a "pro-inflammatory diet" — one which is high on saturated fat, sugar, and processed foods — could influence our mental health in a damaging way. This damage, Lasalle notes, occurs as a result of oxidative stress, insulin resistance, changes in blood flow and inflammation.

"Chronic inflammation can affect mental health by transporting pro-inflammatory molecules into the brain," she said, adding that it "can also affect the molecules — neurotransmitters — responsible for mood regulation."

Inflammation and oxidative stress, she states, can be prevented with the help of fruits, vegetables, nuts, and wine (in moderation) as they tend to contain anti-inflammatory and antioxidant components.

The research team believes that dietary counseling should be provided by health professionals, as changes to eating habits could be beneficial for patients at risk of depression.

But Naveed Sattar, a professor of metabolic medicine at the University of Glasgow, advised more caution. While he is in support of promoting healthier diets, he said the review only looked at observational studies. For a causal link to be established, researchers have to conduct randomized controlled trials.

"The current evidence is not sufficient to prove plant-rich diets can prevent depression as most of the evidence so far simply shows that those with poorer mental health eat worse, so it may be that those more prone to depression also choose less health," he said.

Recently, another study from Italy found that the Mediterranean diet might help older adults live longer, noting a 25 percent lower risk of any cause of death among those who followed it.