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Another Way to Defend Against Depression After the Holidays?

A new link between diet and mood disorders

January was by far the busiest month at the free clinic in California where I worked as an intern, because we always had a flood of new intake patients right after the holidays.

Our clinical supervisors explained that people often got severely depressed during and after the holidays due to fights with family members at Thanksgiving, Christmas or New Year's Eve parties, less sunlight, a big let-down after all the excitement of Thanksgiving and Christmas, big debts from buying presents, or dread at having to return to hated jobs.

But Daniel Reis, Stephen Ilardi and colleagues at Kansas University, writing in Medical Hypothesis, think there may be another reason that mental health professionals see an upsurge of intakes in January: increased sugar consumption at holiday events.

Through a comprehensive literature survey that spanned diverse fields such as epidemiology, psychiatry and physiology, the Kansas researchers found an association between increased sugar consumption and depression. The team hypothesizes that consumption of holiday cookies, cakes, pies and candies triggers a metabolic and immunologic cascade that promotes or aggravates depressive symptoms.

The mood-altering cascade, according to the Kansas group and other investigators, may work something like this: a spike in sugar consumption promotes formation in the liver of compounds such as Free Fatty Acids (FFAs) which in turn stimulate the immune system to increase production of inflammatory proteins—possibly because these liver metabolites of sugar look like toxins to the immune system—which then act directly on the brain to trigger or aggravate depressive symptoms.

According to Andrew Miller of Emory University School of Medicine, inflammatory proteins such as tumor necrosis factor and interleukin reduce the availability of monoamines that regulate mood, such as serotonin and norepinephrine. Although it’s not yet clear whether inflammation directly causes mood disorders in all cases, or is perhaps a byproduct of them (not all depressed patients have increased inflammation), an accumulating body of evidence strongly implicates inflammation in the development of depression and other mental disorders in some patients.

Miller speculates that a link between inflammation and depression may have evolved as an adaptive feature of our brains to protect both individual and group health following traumatic injury or infection. When our distant ancestors were injured or infected (and thus had elevated inflammation), according to Miller, depressive behaviors such as reduced social contact and physical exertion may have lowered the odds that an injured or sick person would be infected by others or, in turn, infect people around them.

In the era of modern medicine, the inflammation/depression response is no longer so adaptive or “healthy,” but our brains have changed very little—if at all—in the roughly 300,000 years that Homo Sapiens have walked the earth. Thus, our brains are still wired to get depressed when inflammatory proteins in our blood are abundant.

So one way to avoid feelings of depression after the holidays may be to avoid sweets at holiday parties.

Depressing, I know, but take consolation in the accumulating evidence that reduced sugar consumption also lessens chances of obesity, fatty liver disease, and cardiovascular disease.

And after all, there’s nothing more sweet than good health, is there?