A 2014 systematic review and meta-analysis of dietary patterns and depression concluded that a healthy diet pattern was significantly associated with reduced odds of depression, but out of the 21 studies they could find in the medical literature, they were able to find only one randomized controlled trial, considered the study design that provides the highest level of evidence. It was the study I profiled in Improving Mood Through Diet, in which removing meat, fish, poultry and eggs improved several mood scores in just two weeks.

We’ve known that those eating plant-based tend to have healthier mood states—less tension, anxiety, depression, anger, hostility, and fatigue. But you couldn’t tell if it was cause and effect until you put it to the test, which they finally did. What could account for such rapid results? Well, eating vegetarian does give you a better antioxidant status, which may help with depression.

Also, as I’ve previously addressed, consumption of even a single carbohydrate-rich meal can improve depression, tension, anger, confusion, sadness, fatigue, alertness, and calmness scores among patients with PMS—but what about long term?

Overweight men and women were randomized into a low-carb, high-fat diet, or high-carb, low-fat diet for a year. By the end of the year, who had less depression, anxiety, anger, and hostility, feelings of dejection, tension, fatigue, better vigor, less confusion, or mood disturbances? The low-carb dieters are represented by the black circles, and the low-fat dieters are represented in the white. These sustained improvements in mood in the low-fat group compared with the low-carb group are consistent with results from epidemiological studies showing that diets high in carbohydrate and low in fat and protein are associated with lower levels of anxiety and depression, and have beneficial effects on psychological wellbeing.

But the overall amount of fat in their diet didn’t significantly change in this study, though. But the type of fat did. Their arachidonic acid intake fell to zero.

Arachidonic acid is an inflammatory omega-6 fatty acid that can adversely impact mental health via a cascade of neuroinflammation. It may inflame your brain. High blood levels in the bloodstream have been associated with a greater likelihood of suicide risk, for example, and major depressive episodes. How can we stay away from the stuff?

Americans are exposed to arachidonic acid primarily through chicken and eggs. But when we remove chicken and eggs, and other meat, we can eliminate preformed arachidonic acid from our diet.

So, while high-quality treatment studies investigating the impact of diet on depression are scarce, there is that successful two-week trial, but even better, how about 22 weeks?

Overweight or diabetic employees of a major insurance corporation received either weekly group instruction on a whole food plant-based diet or no diet instruction for five and a half months. There was no portion size restriction, no calorie counting, no carb counting. No change in exercise. No meals were provided, but the company cafeteria did start offering daily options such as lentil soup, minestrone, and bean burritos.

No meat, eggs, dairy, oil, or junk, yet they reported greater diet satisfaction compared with the control group participants who had no diet restrictions. How’d they do though? More participants in the plant-based intervention group reported improved digestion, increased energy, and better sleep than usual at week 22 compared with the control group. They also reported a significant increase in physical functioning, general health, vitality, and mental health. Here’s that represented graphically, where the plant-based group beat out controls on nearly every measure.

There were also significant improvements in work productivity, thought to be due, in large part, to their improvements in health. So, what this study demonstrated was that a cholesterol-free diet is acceptable, not only in research settings, but in a typical corporate environment, improving quality of life and productivity at little cost. All we need now is a large, randomized trial for confirmation, but we didn’t have such a thing—until now.

Ten corporate sites across the country from San Diego to Macon, Georgia. Same kind of setup as before. Can a plant-based nutrition program in a multicenter, corporate setting improve depression, anxiety, and productivity? Yes, significant improvements in depression, anxiety, fatigue, emotional well-being, and daily functioning. Lifestyle interventions have an increasingly apparent role in physical and mental health, and among the most effective of these is the use of plant-based diets.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.

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