McLean Hospital researchers have added yet another item to the cornucopia of evidence that "we are what we eat," confirming that elements in our diet can affect not just our physical health, but our mental health as well.
Research led by Associate Professor of Psychiatry William A. Carlezon Jr. confirmed the antidepressant-like effects of omega-3 fatty acids, found in cold-water fish like sardines, tuna, and Atlantic salmon, and some plant sources such as canola oil and walnuts.
Carlezon and colleagues also found that uridine, a compound found in sugar beets and molasses, has similar effects. When both compounds were used together, they were found to be effective in lower doses. The research was reported in a recent issue of the journal Biological Psychiatry.
Carlezon's research, conducted with McLean colleagues Stephen Mague, Aimee Parow, Associate Professor of Psychiatry Andrew Stoll, Professor of Psychiatry and head of McLean's Psychiatry Department Bruce Cohen, and Professor of Psychiatry Perry Renshaw, was prompted by clinical studies that have shown omega-3 fatty acids to have beneficial effects on some suffering from major depression. It also follows on anecdotal evidence and broad trends of lower rates of depression in countries that have high fish consumption, such as Scandinavian and East Asian nations.
Depression is a widespread health problem in America. Depressive disorders, which include major depression, bipolar disease, and chronic mild depression, affect 18.8 million Americans, or nearly 10 percent of the adult population, annually. Major depression alone affects 9.9 million Americans annually, and twice as many women as men, according to statistics from the National Institute of Mental Health.
Though the mechanism by which these compounds work is unknown, Carlezon said it is thought that they affect fats in the brain, perhaps by making membranes more resilient and easing the flow of neurotransmitters. An imbalance of neurotransmitters - chemicals that transfer messages between nerve cells - is thought to be a cause of depression.
Carlezon's work is the first to provide evidence through controlled study of animal models that these compounds work as antidepressants. Using laboratory rats, Carlezon and colleagues used methods that in the past have been successful at identifying compounds that work as antidepressants in humans.
The rats were put through a 15-minute swim test during which the animals eventually stopped trying to climb out of the water tank and became largely immobile, moving just enough to keep their heads out of the water. After the test, the rats were dried off with towels, placed in a warm enclosure for 30 minutes, and returned to their cages.
The next day, the rats were retested for five minutes each and those that had not gotten omega-3 fatty acids in their diet or an injection of uridine became motionless much more quickly. Researchers equate the onset of immobility in the rats to depression in humans. The animals that had received either of the two compounds - or lower doses of both - continued to swim around.
"They seem to be protected from the ability of stress to cause depression," Carlezon said.
Since the research was published, Carlezon said he's gotten many calls from people seeking dietary advice. While the effect seems clear, Carlezon said the metabolisms of rats and humans are so different that it's difficult to figure out an equivalent dosage in humans.
Suffice it to say, however, that a weekly fish fry won't be enough. Carlezon said that cultures where this effect has been seen anecdotally eat a lot of fish every week.
"Clearly, we're not talking about a piece of salmon on Friday night," Carlezon said.
Carlezon said the research reinforces the message that we have far more control over our health - both mental and physical - than we often think we do. The foods we eat, he said, can have a significant effect not just on our heart and fat content, but also on how our brain functions.
"It highlights that we have some control over the things we put in our body, and those things will affect how our body will function," Carlezon said. "It puts more responsibility on people to be more careful about what they put in their bodies."
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