New research centers on link between nutrition and brain function
By Bina Venkataraman, Globe Correspondent | December 7, 2009

Not all foods are created equal, whether the goal is having a healthier heart or losing weight. And the same could be true when it comes to what we eat and how depressed or happy we feel, how well we learn, and whether we suffer from mental illness.

A study published last month in the Archives of Internal Medicine divided a group of 106 overweight and obese people into two groups: About half spent a year following a diet low in fat – say goodbye to steak and pastries – and high in carbohydrates (breads, pastas, beans, potatoes, and rice). The other half went for a year on a low-carb, high-fat diet – have a burger, but skip the bun. In both groups, people lost an average of 30 pounds each and generally said they felt happier two months into the diet.

But after a year on the diet, the people who ate less fat and more carbs continued to report feeling happier and less depressed and anxious than they had before. The other dieters, who ate more fat and less carbohydrates, felt their moods decline from the early rise they had noted.

One reason for the difference, the researchers argued, might be that eating more carbohydrates than fat and protein pumps up the production in the brain of serotonin, a chemical that has been linked with improved mood and mental health.

“There’s tremendous interest in how nutrition is related to brain function,’’ said Dr. Perry Renshaw, who formerly directed the Brain Imaging Center at McLean Hospital in Belmont, and currently is a psychiatry professor at the University of Utah School of Medicine. Renshaw is studying whether creatine – a chemical found in fish, meat, and eggs – helps women respond more quickly to antidepressants known as SSRIs (selective serotonin reuptake inhibitors). Examples of SSRIs include Prozac and Zoloft. “It does seem there are natural products that have effects on mood.’’

Scientists haven’t yet developed clinically proven methods to treat mental illnesses and learning impairment with food, but many are working on it.

“Most people thought, until maybe five or 10 years ago, that food’s biggest effect on the brain was through regulation of the cardiovascular system and through the rest of the body,’’ said Fernando Gomez-Pinilla, principal investigator for the Neurotrophic Research Laboratory at the University of California-Los Angeles, and the author of a review published last year in the journal Nature Reviews Neuroscience on food and the brain.

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“The new research shows that the effect of food can be direct on the brain, and that it can be directly related to mood and behavior,’’ Gomez-Pinilla said. Advances in physiology, molecular biology, and brain imaging have allowed more of this research to come to light, he added.

No consensus exists among scientists about which foods are most important to mood and mental health. But a number of studies suggest connections between certain nutrients and brain functions. For example, several studies have linked deficiency in Omega-3 fatty acids – especially one found in salmon and other fish – to psychiatric disorders, including depression, bipolar disorder, dementia, and schizophrenia, as well as learning and memory problems. Researchers have also drawn links between the antioxidants found in blueberries and improvements in mood and the ability to stay focused. Folic acid, found in spinach and boosted via vitamin B supplements, has been associated with the brain functions needed to prevent depression, and learning and memory problems.

Judith Wurtman, co-author of “The Serotonin Power Diet’’ and former director of the Triad Weight Management Center at McLean Hospital, advocates a carbohydrate-rich diet for women, whose brains seem to deplete their store of serotonin more rapidly than men, as a way to prevent depression and anxiety. Wurtman’s research has shown that carbohydrates found in pretzels, popcorn, or bread – when eaten without protein or fat – can increase serotonin, which improves mood. She recommends that women eat plain pretzels, crackers, or bread, daily at around 4 in the afternoon, when they feel themselves lacking energy or becoming irritable. This can be especially helpful to those suffering from premenstrual syndrome.

Some of the most extensive research linking nutrients to mood, learning, and behavior has focused on Omega-3 fatty acids. Omega-3s are an important part of cell membranes vital to brain functions, said Dr. Joseph Hibbeln, acting chief of nutritional neurosciences at the National In stitute on Alcohol Abuse and Alcoholism. The role of those membranes in the nervous system could be compared to the plastic that surrounds wires in the electrical system of a house. Without them, the neurons lack protection and do not function as well.

“If you eat a diet that is deficient in Omega-3 fatty acids, it can alter your brain,’’ Hibbeln said. “Omega-3 fatty acids can actually reduce suicidal thinking and depression,’’ as well as violent behavior.

Over the past century, Hibbeln added, American consumption of foods with Omega-3 fatty acids, such as fish, has declined, while we’ve eaten more fast food and processed foods rich in omega-6 fatty acids (found in soybean oil and seed oils). The omega-6 fatty acids not only do not help brain function, they harm it – by pushing Omega-3 fatty acids out of body tissue, according to Hibbeln.

As neuroscience advances, researchers hope to better understand how food and diet influence mental health and behavior. But understanding how nutrients change brain chemistry will not necessarily mean scientists will know how to treat psychiatric disorders with food. The challenge lies on the level of human decision-making.

“Our diet is very complicated,’’ said Robin Kanarek, a psychology professor at Tufts who is conducting research with Renshaw. “We are not just eating one food.’’ With the exception of experiments such as the one popularized in the film “Super Size Me,’’ it’s difficult to measure the effect of particular foods because people’s diets vary from day to day and month to month. Exercise, stress, and other aspects of lifestyle and the environment can affect how the brain responds to nutrients, and they also affect mood and behavior. And an important, lingering question is what role diet plays relative to genetic predisposition to psychiatric and behavioral disorders. All those factors make it difficult to use food as a treatment for mental illness.

“I think the big picture is that we may never know the role of food,’’ said Renshaw. Part of the problem, he added, is that pharmaceutical companies have no incentive to finance the large clinical trials required to prove whether particular foods can treat a mental illness, comparable to the trials done for testing drugs. Government funding, he said, has also been inadequate.

“We’d all like to think there’s some food that will make people feel better quickly like the drugs do,’’ said Bill Carlezon, a psychiatry professor at Harvard Medical School and director of the behavioral genetics laboratory at McLean Hospital. “I personally don’t like taking drugs; I would try the food first.’’

Bina Venkataraman can be reached at bina@globe.com.