The Pillars of Health

"You are what you eat" may be a simple truth, but the path to proving that diet influences not just the heart but also the brain, with behavioral consequences, has been long and complex. Mothers insist that sugar hypes their kids up, but study after study disproves any direct cause and effect. Sure, dementia is a disease of oxidation and inflammation ending in brain cell death, but tackling it with antioxidants, while logical, doesn't work.

Larger questions of diet and behavior are tough to study. A regimen of junk food is related to diabetes, obesity, high blood pressure, heart disease, and dementia, but is it the fat? The sugar? The salt? The preservatives, or the azo food dyes? Consumed how and when? And is diet assessed by recall, which is subject to error?

Only in the last decade has research definitively proved that the components of natural foods are different from those of processed foods and are handled differently, especially by bacteria in the gut. And, oh yes, those bugs talk to the brain. And talk!

Hard evidence that diet influences behavior has now reached such a critical juncture that clinicians and researchers from all over the world recently gathered in Bethesda, Maryland, to establish an International Society for Nutritional Psychiatry Research. "Although the determinants of mental health are complex, the emerging and compelling evidence for nutrition as a crucial factor in the high prevalence and incidence of mental disorders suggests that diet is as important to psychiatry as it is to cardiology, endocrinology, and gastroenterology," the prime movers declared in the British journal The Lancet Psychiatry. If nothing else, the complexity of the brain and the influences on it demand the kind of collaborative approach that grows from bringing together experts in fields as diverse as basic biochemistry and large-population dietary-pattern research.

Two American pioneers in the biochemistry of fatty acids—William Lands, an early expert on the phospholipid composition of cell membranes, and Michael Crawford, who probed the role of brain fats in inflammatory responses, both now 87—sat with field scientists such as Joseph Hibbeln. From his nutritional neuroscience lab at the National Institutes of Health, Hibbeln studies levels of omega-3 and omega-6 fatty acids in the brains of U.S. military members.

The closer scientists look at cell operations, the more they see dietary nutrients influencing body systems, including the brain. The human brain uses omega-3 fatty acids to build nerve-cell membranes and for nerve-cell signaling. But the amount of omega-3 in the American diet has plummeted; the industrialization of the food supply pours omega-6 fats into foods largely through the use of corn and soybeans as animal feed and as sources of inexpensive vegetable oils. Omega-6 and omega-3 fats more or less fight each other for space on cell membranes; shifting the balance of the two nutrients can have a profound effect on the fatty acid content in the brain.

Does the fatty acid shift affect behavior? Studies of men in Japan and U.S. service members show that those with the lowest omega-3 fatty acid content in their cell membranes have the highest rates of suicide. In other research, depression symptoms lessen when patients consume supplements containing the omega-3 fat EPA (eicosapentaenoic acid). It's not yet clear, however, whether consuming supplements is superior to increasing fish intake.

Population studies show that people who consume more traditional diets—the Mediterranean pattern is the most studied—have lower rates of depression than those consuming a Western diet, high in processed foods. Traditional diets are typically low in omega-6 fats and supply more fish and seafood (rich in the brain nutrient iodine as well as omega-3s) than a Western diet. In clinical studies at the University of Melbourne, Felice Jacka has significantly reduced depression symptoms among patients by feeding them a modified Mediterranean diet.

The conference spotlighted other nutrients that may take on expanded roles in reducing psychiatric symptoms. For example, the minerals magnesium and zinc are wasted by the body during periods of high stress. A mineral-rich supplement given to survivors of natural disasters in New Zealand is fostering recovery from trauma by dampening anxiety.

The B vitamins known as folates are needed to make neurotransmitters, but many individuals have an inherited inefficiency in processing dietary folates into the methylated folate needed in the brain. Studies of methylated folates now underway show that supplements containing the specially formulated nutrient can overcome the inherited metabolic bottleneck and curb depression.

Diet also has a profound effect on the composition of the microbiome, the influence of which on brain health and behavior is now the subject of intense study around the world. Gut bacteria not only communicate with the brain directly by releasing neurally active chemicals, they also play a major role in inflammatory processes, implicated in many brain disorders including depression. It is likely not a coincidence that irritable bowel syndrome (diarrhea, constipation, or both, without a currently known medical cause) is highly associated with symptoms of anxiety and depression. Crowdsourced data from the American and British Gut Projects along with the plummeting cost of microbiome mapping is expected to significantly boost understanding of the gut-brain connection.

Perhaps the most important accomplishment of the conference was to get clinicians to think in research-oriented ways and to get researchers to give clinicians practical and useful information for patients.

The Chicken or the Egghead?

Rather than convince people to change what they eat, a more far-reaching approach to improved health, and notably brain health, may be to change food itself. Joseph Hibbeln of the National Institutes of Health proposes raising chickens on feed low in omega-6 fatty acids and loaded with omega-3s. He's also exploring use of a sunflower oil rich in oleic acid—which makes it similar in composition to olive oil but cheaper—for cooking and salad dressings. Lowering the dietary load of omega-6s may bring the omega-fat ratio back to the healthier levels our ancestors likely consumed, lessening the population burden of cognitive and mood disorders.

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