Thursday, November 5, 2009

More evidence about the impact of nutrition on mood

An important paper was just published by Akbaraly et al. in The British Journal of Psychiatry, in which 3486 people were followed prospectively for 5 years, with an analysis of nutritional habits and depression symptoms. Here's a link to the abstract:

The data showed that individuals consuming a diet rich in "processed foods" (such as sweetened desserts, fried food, processed meat, refined grains, and high-fat dairy products) had a much higher rate of depression compared to those consuming a diet heavily loaded with vegetables, fruits, and fish.

The analysis controlled for confounding factors such as gender, age, caloric intake, marital status, employment grade, education, smoking, physical activity, hypertension, diabetes, and cardiovascular disease. A component of the analysis also strongly suggests that the association is not due to reverse causation, of depression leading to worse nutrition. Rather, the analysis strongly suggests that poor diet is a component of causation: that is, poor diet directly increases the risk of becoming depressed, or of having worse depressive symptoms.

Those in the third of people with diets highest in processed foods had a 58% higher chance of having clinical depression compared to the third of people with the healthiest diets.

So, once again, more evidence-based advice to eat healthily in order to protect your mental health:
-more vegetables, fruits, and fish
-less sweets, fried foods, white flour, whole milk, ice cream, etc.


Anonymous said...

Hi Dr. K.,
How do they know the diet is causal and not that those who are depressed have diets high in processed food for whatever reason...i.e.too tired to cook from scratch, craving certain foods because of meds or mood disorder etc.?

GK said...

It is certainly true that most people have less healthy nutrition, for a variety of reasons, during depressive episodes. But here is why this study goes further, to show nutritional behaviour directly affects future mood:

The authors found no association between a previous report (past history) of depression, and dietary patterns 6 years later. This shows that, in their sample, a history of depression does not predict future negative dietary habits.

The following is more directly pertinent to your question, though: part of the analysis looked at dietary habits in 1997-1999 among only those subjects who were NOT depressed at this 1997-1999 time point. Among these originally non-depressed subjects, a strong association remained between unhealthy dietary habits and developing depression by 2002-2004.

These two components of their analysis support the conclusion that unhealthy diet directly increases the risk of becoming depressed in the future, and that the association found was not merely due to current active depression causing a less healthy diet.