Last week Penn State researchers reported a study indicating that eating junk food could worsen a bad mood, though it had no effect on a good one. Presented Friday at a conference of the American Psychosomatic Society, the result was based on surveys of 131 young women concerned about their diet and self-image.
Covered in a few press outlets like LiveScience and the New York Daily News, this was a much smaller enterprise than the recent six-year European study of fast food and depression in 12,000 people. Still, it stood out by collecting data in real time throughout a week of normal daily activities. A hand-held device was used to prompt participants to report their mood and eating habits. The real-time data allowed the conclusion that improper eating preceded rather than followed the worsening in mood.
With the health costs of depression amounting to $44 billion in the U.S. alone, there has been a tremendous amount of research into questions like these. Many nutritional factors have been suggested: carbohydrates, sugars, and alcohol; trans and saturated fats rather than oils from fish, nuts, and vegetables; and lack of certain amino acids, minerals, and B vitamins.
There are just as many notions for how food could affect mood. For example, omega-3 fatty acids might influence endocannabinoid activity on the CB1 receptor, which is best known as the cellular target for marijuana. The drug rimonabant has the opposite effect on it, and was shown to be a weight loss aid twice as effective as Xenical. Alas, this weight loss was still only 11 pounds, and came with significant depression-inducing side effects that forced the drug to be withdrawn. Researchers are now developing similar drugs which should cause weight loss by affecting CB1 receptors throughout the body, but which cannot enter the brain to cause depression.
Another idea is that leptin — a hormone produced by fat which decreases the desire to eat — has a positive role on mood and cognition, but when people accumulate abdominal fat it can cause them to become resistant to this hormone much as they can become resistant to insulin. Nonetheless, the synthetic form, metreleptin, didn't seem to affect mood while reducing body weight up to 12% in a combination treatment.
What the Penn State group has done is to provoke a moment of thought, calling some more attention to the negative effect of some foods rather than the deficiency of others. The Hippocratic method — paying close attention to the patient over a period of time and using basic inductive reasoning — is as old as medicine itself. Using handheld devices to collect real-time data can extend this method into survey-based research, and may help researchers to give specific foods the credit or blame they deserve.