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Trans fats linked to higher risk of depression

Here's food for thought: a new study suggests that the fats you eat may influence your risk of depression. Researchers found that people whose diets were high in trans fats had a raised risk of depression, while those who ate more unsaturated fats - from olive oil, in particular - had a lower risk.

What do we know already?

We all need to eat some fat. Fat gives us energy and helps to transport vitamins around the body. But some types of fat can be harmful. For example, eating foods high in trans fats and saturated fats can raise the level of bad cholesterol in your blood, increasing your risk of heart attacks, strokes, and related problems.

Unfortunately, these 'bad' fats are common in Western diets.Trans fats are found in hard margarine, fast food, pastries, doughnuts, and other baked goods. Sources of saturated fats include butter, hard cheese, cream, ice cream, and meat fat.

Besides raising the risk of heart problems, these fats might also play a role in depression, say researchers. Supporting such a connection are studies showing that depression is less common in Mediterranean countries, where people eat less saturated and trans fats and more unsaturated 'healthy' fats, which are found in olive oil and fish, for example. This is a central component of Mediterranean-style diets, which are also high in fruits and vegetables. Although many factors contribute to people's risk of depression, could their fat consumption be one of them? To explore this, a new study followed 12,059 graduates of Spanish universities for several years. The participants filled out questionnaires every two years, answering questions about their diet, lifestyle, health, and whether they'd been diagnosed with depression.

What does the new study say?

The higher the amount of trans fats people ate, the greater their risk of depression. And those who consumed the highest levels of trans fats were 48 percent more likely to be diagnosed with depression than those who consumed the least.

The researchers found an opposite relationship with unsaturated fats. The more of these 'healthy' fats people ate, the lower their risk of depression.

When looking at specific sources of fats, the researchers found that butter consumption was linked with an increased risk of depression, whereas olive oil consumption was associated with a lower risk.

How reliable are the findings?

This was a big, well-conducted trial. However, this type of study can't show cause and effect, so it can't prove that fats raised or lowered people's risk of depression. It can show only that there might be a link.

The researchers took into account other factors that might have affected people's risk of depression.These included how much they exercised, their overall calorie intake, their body mass index (BMI), whether they smoked, and whether they adhered to a Mediterranean-style diet overall. But it didn’t look at people’s economic status or where they lived. Dietary choices might simply reflect having less money, or living in a more deprived area. Both of these things could increase the chances of depression.

The study also relied on data compiled from questionnaires, which isn't the most reliable method for gathering information, particularly on what people eat. Also, they only analyzed how much fat people consumed at the start of the study, so they don't know how changes in people's diets might have influenced their findings.

Finally, this study only included people living in Spain, who typically eat much less trans fat than people in the UK, the US, and countries with similar diets. Indeed, trans fats made up only 0.4 percent of the participants' average energy intake. This suggests, say the researchers, that trans fats could have an even larger effect on depression in countries such as the UK. But studies will need to explore this.

Where does the study come from?

The study was done by researchers at universities in Spain and the Netherlands. It appeared in a journal called PLoS ONE, which is published by the Public Library of Science. The study was funded by the University of Oslo.

What does this mean for me?

We already know that your choice of fats can affect your heart health.This study suggests it might play a role in your mental health, too.


Sanchez-Villegas A, Verberne L, De Irala J, et al. Dietary fat intake and the risk of depression: The SUN Project. PLoS ONE. 2011; 6: 16268.

To learn more, see our information on depression.

Jan 27, 2011