Dietary Fat Intake and the Risk of Depression

Many studies have shown better mental function to be correlated with healthy nutritional habits. Recently, depression has been shown to be directly related to Western food habits, mainly consumption of saturated fats and fewer fruits, vegetables and whole grains. A study was conducted to assess the effect of dietary fat and different fat subtypes on risk of depression. The results showed a direct association of consuming monounsaturated and trans-unsaturated fat with occurrence of depression, whereas consuming polyunsaturated fat showed an inverse relationship with depression.

Depression is a mental disorder with a high prevalence in developed countries. A recent study showed an inverse relationship between depression risk and a diet consisting of vegetables, fruits, cereals, fish and legumes taken by South Europeans, as compared to those in the northern part of Europe. Depression and cardiovascular diseases have been shown to share common risk factors in terms of nutritional habits, with healthy lipids like polyunsaturated fatty acids reducing the risk. Therefore, the authors conducted a study to assess the effect of consumption of fat and different varieties of fat on the risk of occurrence of depression.

* Healthy volunteers without any clinically diagnosed disease were recruited for the study, and 12,059 participants were followed up for a period of 10 years for any diagnosis of depression or intake of anti-depressants.
* Dietary consumption was measured at the baseline and then at the time of diagnosis of depression or intake of antidepressant medications or end of follow-up period, whichever came earlier.
* A questionnaire was used to gather information on physical activity, lifestyle, medical and socio-demographic variables.
* The study checked whether the participants were sticking to the Mediterranean Dietary Pattern (MDP) including vegetables, fruits and nuts, fish, meat and meat products, legumes, alcohol and dairy intake.

Key findings
* A significant decrease in the incidence of developing depression was observed with an increased consumption of polyunsaturated fat. The risk decreased linearly over the years and there was a significant decrease in risk at the end of the study, when compared with the initial year of study onset.
* A similar trend of inverse association was also observed with intake of monounsaturated fat.
* Consumption of butter had an association with a higher risk of depression, but consumption of olive oil was associated inversely with a risk of depression.
* A significant increase in the incidence of developing depression was observed with an increase consumption of trans unsaturated fat. The risk increased linearly over the years and there was a significant increase in risk at end of the study, when compared with the initial year of study onset.

Next steps/Shortcomings
The dietary intake values were taken only once, at the time of entry, which could have altered in the volunteers as the study progressed over time. This variation was not taken into account while establishing the correlation of dietary fat intake and occurrence of depression. Besides, it was the volunteers who confirmed the occurrence of depression or intake of antidepressant drugs; it was not validated from the concerned physician.

The study showed a protective effect of dietary consumption of polyunsaturated fat on the incidence of depression; there was a direct correlation between risk of depression and consumption of monounsaturated fat and trans unsaturated fat. Mediators of inflammation have been shown to interfere with neurotransmission in the brain, leading to depression; intake of trans-unsaturated and monounsaturated fats can aggravate this alteration. On the other hand, consumption of healthy fats like polyunsaturated fat can play a protective role in depression, as well as in metabolic diseases like diabetes or cardiovascular diseases like heart attack or heart failure. A similar positive correlation was also observed with the consumption of olive oil, in this study. However, further clinical trials would be required to substantiate the effects observed with regard to the effect of dietary fats on the risk of depression.

For More Information:
Dietary Fat Intake and the Risk of Depression: The SUN Project
Publication Journal: PLos One, January 2011
By A.S. Villegas, L. Verberne, J. De Irala, et. al; University of Las Palmas de Gran Canaria, Spain, University of Navarra, Pamplona, Spain and Wageningen University, Wageningen, The Netherlands

*FYI Living Lab Reports Are Summaries of the Original Research.

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