The Mediterranean Diet and Depression
Should we break out the olive oil?
Posted October 8, 2009
A few days ago a study appeared in the Archives of General Psychiatry linking strong adherence to the Mediterreanean Diet to a lower incidence of depression in a sample of 10,000 young adults in Spain and, boy, did the media go crazy!
At last count there are 118 news stories touting this report. Here are three examples from leading media outlets
Here is some representative veribage from one of the stories...
Jetting to the sunny climes of the Mediterranean couldn't hurt if you feel a bout of depression settling in.
But a new study in the Archives of General Psychiatry finds that if your aim is to minimize your risk of depression in the first place, you might stay right where you are and make your plate look like it's been to the Mediterranean. You should scale back on the meats and dairy fats, eat some nuts, and increase your consumption of fish, vegetables and legumes doused in olive oil.
Oh, and pour yourself a glass of wine. Not half a bottle; one glass, maybe two.
Dear blog readers, I have now read the actual study, as opposed to the breathless coverage of the study, and I believe that it is far too early to break out the olive oil. For three main reasons:
(1) The researchers did not control what the participants were eating. People could adopt or not adopt a Mediterrean diet as they saw fit. As it turns out, people who were good about adhering to a Mediterrean diet were also more likely to be male, more likely to be married, and more likely to be physically active. These characteristics are all likely to be protective against depression (a condition that is more common among females, people who are divorced or separated, and people who are sedentary). Now the researchers tried to control for these factors statistically in order to be more confident that the effects were from the diet and not from other characteristics. While that is better than nothing, the researchers acknowledge that people who adhere to this diet are probably different from people who don't adhere to the diet in number of other ways. As it stands, the study does not establish that the Mediterrean diet is itself responsible for any reduction in depression.
(2) If you read the study carefully, the assessment of diet was itself quite thin. People were asked to self-report a "semi-quantitative" food frequency questionnaire with 136 food items once every two years. If someone asked you how often you eat 136 different food items, do you think you could report them all accurately? Are people completely aware of what they eat? If somone asked you how often you eat unhealthy foods or healthy foods, would you not feel at least a slight pull to round down on the former and round up on the latter. The authors and the media have behaved as if actual food intake was measured, when only people's fallible report of what they eat regularly was measured. These are not the same thing!
(3) The researchers in the article (and the media coverage) could only speculate about which specific chemicals in the Mediterranean diet are helpful.
So, I will wait to break out the olive oil when this result is replicated in a carefully controlled study. As it stands, I believe this episodes illustrates more about our tendency to turn food into a pharmaceutical than any real knowledge about the links between depression and diet.