Why The Mediterranean Diet May Be Overhyped For Mental Health, From A Psychiatrist

Our diet has undergone radical changes in the past century.

Born in 1910 and raised in a rural New England farm town, my grandmother ate two soft-boiled eggs and buttered toast every morning for breakfast, ground her own hamburger with a medieval-looking device she clamped to the kitchen counter, and kept an old coffee can full of bacon fat by the stove for cooking.

By the time she passed away in 1993, all three of these foods were falling out of favor with the American public and had been officially condemned as dangerously unhealthy.

The first U.S. Dietary Guidelines, released in 1980, warned that saturated fat and cholesterol caused obesity and heart attacks, so they advised Americans to "moderate your use of eggs," "limit your intake of butter," and "trim excess fat off meats."

Like a perfect storm, the powerful forces of food industrialization, growing anti-meat sentiment, and fat and cholesterol phobia collided and have been feeding on each other for the past 50 years, dramatically transforming our nutritional way of life. Since most other nations pattern their food guidelines after the U.S. guidelines, this shift away from animal fats and toward refined carbohydrates and vegetable oils meant that the whole world was about to take part in a grand nutrition science experiment—with devastating consequences.

Characterized by an abundance of calorie-dense, nutrient-poor foods and beverages, the so‑called standard American diet (I'll take the liberty of referring to this as the "SAD diet" going forward), isn't just an American problem anymore—this modern atrocity has been exported to all four corners of the Earth, endangering the physical and mental health of people everywhere.

Unfortunately, we don't have much concrete information about the mental health of people prior to the modernization of our diet, but what little we do have suggests that our mental health was more robust in the past than it is today.

Industrial globalization has made it difficult to locate people in this century who eat entirely off the land, but in the middle of the last century, there were still pockets of dietary sanity to be found.

In a 2003 paper titled "Nutrition and Schizophrenia1," University of Sheffield psychiatrist Malcolm Peet, M.D., highlighted interesting studies from Taiwan, Tonga, Trinidad, Papua New Guinea, Malawi, and Australia's Gold Coast, all of which suggested that schizophrenia was far less common in people who fed themselves by hunting, fishing, and subsistence farming. As Peet wrote, "It is remarkable that studies of truly Indigenous populations are virtually unanimous in reporting very low rates of schizophrenia."

For example, signs of schizophrenia were exceedingly rare among non-Westernized Pacific Islanders in the 1950s. Of 60,500 inhabitants examined, researchers identified only two individuals with psychotic behavior (0.003%), whereas the prevalence of psychosis among Europeans of the same time period was 67 times higher2 (0.2%).

The relatively new specialty of nutritional psychiatry was established on the belief that the deterioration in the quality of our diet is largely to blame for the deterioration in our mental health.

The story of how the Mediterranean dietary pattern and its familiar "whole grains good, animal fats bad" philosophy became implanted in our collective psyche is told masterfully by investigative journalist Nina Teicholz in The Big Fat Surprise.

Part wishful thinking, part wild guess, the Mediterranean dietary pattern essentially began as a romantic theory about what we should eat, inspired by cherry-picked aspects of Mediterranean traditions and propped up by unscientific studies conducted in the 1950s and 1960s by Ancel Keys, M.D., a University of Minnesota researcher who believed that saturated fat caused heart disease.

The creators of the Mediterranean diet didn't start with a thoughtful examination of the nutritional risks and benefits of individual foods, use that information to design a dietary pattern, and then test that pattern in human clinical trials to see if it improved health.

Instead, they observed that people living in countries along the north shore of the Mediterranean Sea generally seemed to be healthier than Americans, assumed that some of the differences in the way they ate must be responsible for their superior health, and then designed a dietary pattern that they thought represented the healthiest aspects of those culinary traditions.

The Mediterranean diet has since been extensively tested in dozens of human clinical trials for physical health conditions such as obesity, cardiovascular disease, and Type 2 diabetes, and has consistently outperformed the SAD diet, earning the trust of the medical community and nutrition policymakers alike.

As for mental health conditions, although studies testing the Mediterranean diet's potential to prevent or treat memory and cognitive health issues have produced mixed results5, three clinical6 studies7 have now demonstrated that switching from a poor-quality SAD diet to the Mediterranean diet can improve symptoms of clinical depression when added to standard psychiatric treatment (medication and/or psychotherapy). The science is clear: The Mediterranean diet is healthier than the SAD diet, so if you currently eat a SAD diet, switching to the Mediterranean diet would be a solid step in the right direction.

What makes the Mediterranean diet healthier than the SAD diet? Is it the nuts? The olive oil? The red wine? We really don't know. Those who advocate for the Mediterranean diet speculate that it is superior to the SAD diet because it is lower in saturated fat, trans fats, and added sugars; richer in essential nutrients; higher in fiber; and chock-full of colorful fruits and vegetables brimming with phytonutrients—naturally occurring plant chemicals believed to have unique anti-inflammatory and antioxidant properties8. However, there are so many differences between these two dietary patterns that there is no easy way to determine which aspects of the Mediterranean diet are responsible for its health benefits.

But the Mediterranean diet's biggest blind spot is that it pays far too little attention to metabolic health. In other words, it contains too much carbohydrate for people with insulin resistance to safely process, resulting in higher insulin levels that can damage brain metabolism over time. The word "metabolism" refers to the complicated collection of chemical reactions our cells use to turn food into energy. Since the brain is an energy hog, if its metabolic machinery can't generate enough power to meet its needs, it can and will malfunction.