Diet and Depression: Studies Find Eating Plant-Based Has Mental Health Benefits

Although that donut may put a smile on your face in the moment, it may be a short-lived high. That’s according to a growing body of research linking mental health and our diet. The findings link the foods that are healthier for your body as also benefiting your mood, even in depressed patients.

More than 17 million Americans over the age of 18 are affected by mood disorders, and according to Harvard Health researchers, the connection between what we eat and how we feel is irrefutable, especially among people diagnosed as clinically depressed or who suffer from other brain or mood disorders.

What it boils down to is that what we eat matters for every aspect of our health, but especially our mental health. Several recent research analyses looking at multiple studies support that there is a link between what one eats and our risk of depression, specifically. According to one analysis:

“A dietary pattern characterized by a high intake of fruit, vegetables, whole grain, fish, olive oil, low-fat dairy and antioxidants and low intakes of animal foods was apparently associated with a decreased risk of depression," according to the Harvard report. Meanwhile:

"A dietary pattern characterized by a high consumption of red and/or processed meat, refined grains, sweets, high-fat dairy products, butter, potatoes and high-fat gravy, and low intakes of fruits and vegetables is associated with an increased risk of depression.”

Data linking diet and depression continues to point to the benefits of eating a cleaner, predominantly plant-based diet for improved mental health.

Recent research also found a higher risk of addiction to processed foods than whole foods. The potential to over-consume unhealthy foods presents its own set of risks that may affect the mental health or perpetuate addictive traits often connected with depressive disorders.

Studies, like those based on the decades-long Nurses' Health Study, found links between depression and a diet that is high in sugar, soft drinks, refined grains, and red meat, particularly in middle-aged and older women.

According to a newer study published in the journal PLOS One, a Mediterranean diet—high in fruits, vegetables, lean proteins, nuts, and seeds, and low in refined carbohydrates, saturated fats, and sugar—appears to reduce symptoms of depression. The Mediterranean diet has been ranked number one by US News and World Report for the last four years.

“It's generally accepted that the folks in countries bordering the Mediterranean Sea live longer and suffer less than most Americans from cancer and cardiovascular ailments. The not-so-surprising secret is an active lifestyle, weight control, and a diet low in red meat, sugar, and saturated fat and high in produce, nuts and other healthful foods,” U.S. News and World Report noted in its best diet ranking for 2021. “The Mediterranean Diet may offer a host of health benefits, including weight loss, heart and brain health, cancer prevention, and diabetes prevention and control.”

The publication highlights an important clarification, “There isn't ‘a’ Mediterranean diet. Greeks eat differently from Italians, who eat differently from the French and Spanish. But they share many of the same principles.” These principles are built around the slow food ideal: fresh, local food, minimally processed. And while meat and dairy have long been part of these regional diets, they’re not dominating. Fruits, vegetables, grains, and beans are at the heart of all of these diets—even in France where animal products, particularly dairy, have been a mainstay.

Unlike other diets that may be more structured, particularly if weight loss is the goal, the Mediterranean diet is more of a blueprint: Aim for whole plant foods, and avoid the junk.

That study found that the group on the Mediterranean diet, compared with the control group, saw depression symptoms improve over a three-week period. Researchers noted a shift in depressive symptoms, moving the group from moderate to normal range. They also saw lower levels of anxiety and stress compared with the control group.

"We were quite surprised by the findings," Macquarie University in Sydney, Australia researcher Heather Francis, told NPR. "I think the next step is to demonstrate the physiological mechanism underlying how diet can improve depression symptoms."

There have been other studies that looked at the Mediterranean diet and depression, too. In 2013, a meta-analysis of 22 studies found the diet was linked with a lower risk of depression. A 2017 study came to a similar conclusion, although this one went a step further and assessed the depression risk associated with a diet high in red meat, refined grains, sugar, and dairy. Those foods were linked to an increased risk of depression.

Last month, researchers in the Netherlands found a healthy diet improved the mental quality of life in adults diagnosed with multiple sclerosis (MS). The study, published in the journal Nutritional Neuroscience, looked at the eating patterns of subjects with MS — whether they had already followed a specific diet or adapted to help manage their MS symptoms. These included low carbohydrate diet, high carbohydrate diet, high-fiber diet, gluten-free diet, sugar-free diet, vegan diet, vegetarian diet, Atkins diet, Jelinek diet (overcoming MS diet), and Paleo diet.

According to the researchers, the subjects with the highest mental health quality of life scores were also those who consumed a high-fiber diet. The vegetarian diet had the highest physical quality of life score. “Our findings in this sample of the Dutch population of MS patients confirm those of an international [study], in which diets that were characterized by ample amounts of vegetables, fruits, [fiber] and healthy fats were associated with better physical and mental health,” the researchers noted.

“Longitudinal studies and randomized controlled trials are needed to test whether starting an MS-diet or taking measures to better adhere to the general dietary guidelines improves [quality of life] and reduced disease activity and slows disease progression,” they added.

"There is consistent evidence for a Mediterranean-style dietary pattern and lower risk of depression," says Harvard’s Chocano-Bedoya. And she says there are other benefits to a healthier Mediterranean-style diet.

"For instance, the Mediterranean diet has also been associated with lower blood pressure, better cognitive function, and lower incidence of diabetes and cardiovascular events," says Chocano-Bedoya. "I would recommend an overall healthy, high-quality dietary pattern, such as a Mediterranean-style diet, not only for the potential to reduce depression risk but also for overall lower risk of other chronic conditions, which in themselves may later increase the risk of depression."

To learn how to adopt a 'greener' Mediterranean diet with fewer animal products and more plants, which has been shown to be even healthier than the traditional version, click here.