Trans-Fats Linked to Increased Depression Risk

Findings Have Major Implications for Americans

Deborah Brauser

January 28, 2011

January 28, 2011 — Consumption of trans-unsaturated fatty acids (TFAs or trans-fats) has been linked to a significantly increased risk for depression. On the other hand, olive oil, monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs) appear to have a protective effect and lower depression risk, new research suggests.

Spanish investigators from the University of Las Palmas de Gran Canaria found that compared with their counterparts who consumed diets low in TFAs, individuals with elevated levels of trans-fats had a 48% increased risk for depression.

These findings, say researchers, suggest cardiovascular disease and depression "may share some common nutritional determinants related to subtypes of fat intake.

Dr. Almudena Sánchez-Villegas

"The results were not surprising [and] I think the message is clear: 'try to eat healthy,'" lead study author Almudena Sánchez-Villegas, PhD, told Medscape Medical News.

"Avoid some types of fats, such as trans and saturated fatty acids, and increase the intake of polyunsaturated and monounsaturated fat; it's better to consume olive oil than margarine or butter, better to use low-fat dairy than high-fat dairy, and better to eat fish than to consume meat or meat products; avoid fast and processed foods and commercial bakery; and try to increase your consumption of fruits, vegetables, and nuts," she said.

Following this advice, she added, will not only protect against cardiovascular disease but, as suggested by this and other recent research, also mental illness.

The investigators note that this is the first cohort trial to assess "such a broad spectrum of fat subtypes in relation to depression risk."

The study is published in the January issue of PLoS ONE.

150 Million Affected

"Depression affects more than 150 million people worldwide. However, relatively few [longitudinal] studies have analyzed the effect of diet on this disease," said Dr. Sánchez-Villegas.

She added that several previous studies have suggested a link between cardiovascular disease and depressive disorders via inflammatory, endothelial, or metabolic processes.

"The adverse effects of trans-fatty acids on cardiovascular disease are thought to be mediated by increases in proinflammatory cytokines and endothelial dysfunction. We decided to analyze the possible association between trans-fatty acids and depression because low-grade inflammatory status and endothelial dysfunction are common among depressed patients," Dr. Sánchez-Villegas explained.

"On the other hand, olive oil contains some bioactive polyphenols with important anti-inflammatory properties. This anti-inflammatory capacity...could also improve the function of the endothelium."

The researchers evaluated data on 12,059 university graduates (mean age, 37.5 years; 58% female) from the Seguimiento Universidad de Navarra (SUN) project, an ongoing study initiated in 1999 to assess the effect of several dietary factors and lifestyle variables on chronic diseases, including cardiovascular disease, hypertension, obesity, and depression.

Mailed questionnaires are sent biannually to all SUN participants. Those selected for this analysis completed at least the baseline questionnaire and 1 follow-up questionnaire before May 2010.

Participants were queried about intake of fatty-acids, PUFAs, TFAs, MUFAs, olive oil, seed oils, butter, and margarine. They were also asked about medical, sociodemographic, and lifestyle variables.

None of the participants had been diagnosed as having depression before study entry. They were classified as new cases of depression if, at follow-up, they reported they had been diagnosed as having the disorder or had initiated therapy with antidepressants.

Detrimental Effect

Results showed that 657 new cases of depression were identified during a median follow-up time of 6.1 years.

Multivariable-adjusted analysis showed a significant dose-response relationship between TFA intake and depression incidence (trend, P = .003).

The magnitude of this association was robust and persisted [and] results did not substantially change after adjusting for potential lifestyle or dietary confounders, including adherence to a Mediterranean dietary pattern.

"The magnitude of this association was robust and persisted [and] results did not substantially change after adjusting for potential lifestyle or dietary confounders, including adherence to a Mediterranean dietary pattern," investigators report.

A statistically significant inverse dose-response relationship was obtained for total MUFA (trend, P = .05) and PUFA (trend, P = .03) intake. Olive oil was also inversely associated with depression risk (P = .03), although "this relationship was attenuated after adjustment for the adherence" to a Mediterranean dietary pattern.

"Our results showed a protection of cardioprotective fats (PUFA and MUFA) and a detrimental effect of TFA on depression risk. However, our findings need to be confirmed by further prospective studies," the researchers write.

Dr. Sánchez-Villegas reported that the investigative team has received several grants from the Spanish Ministry of Health to further assess the association between dietary factors and depression.

"We are [also] evaluating the effect of diet and physical activity on quality of life in the SUN project," she said.

'Major Implications' for America

"I think this is a really important study," Felice N. Jacka, PhD, research fellow at Deakin University in Melbourne, Australia, told Medscape Medical News.

Dr. Felice Jacka

"The finding regarding the [TFA] is of particular importance. There are no data that I'm aware of to date that have actually looked at its intake and risk of mental health problems," said Dr. Jacka.

"I think this adds to the body of literature that's been developing for the last 12 months showing that dietary factors are a potential real importance in both the risks of mental health and the progress of mental illnesses. And now we've got a little bit more information on specific nutrients."

She noted that TFA is "a particular problem in the food chain," especially in the United States.

A recent study conducted by Dr. Jacka and reported by Medscape Medical News showed that a "whole" diet characterized by vegetables, fruit, whole grains, and high-quality meat and fish decreases both depression and anxiety. It also showed that those with a more "Western type diet" high in refined or processed foods and saturated fats had an increased risk for depression.

"In Australia we have very low levels of trans-fatty acids. In Spain it would seem that they have moderate levels, and in America they have extremely high levels, relatively speaking," she said.

This new finding of a very clear dose-response relationship between the level of trans-fatty acids and risk for depression over time has major implications for America.

"This new finding of a very clear dose-response relationship between the level of trans-fatty acids and risk for depression over time has, I think, major implications for America."

Dr. Jacka said that an association between dietary intake and mental health risk has now been shown "all across the world," including in Spain, Australia, the United States, Britain, Norway, and Japan.

"It's been found in young people, middle-aged people, and the elderly. And the effect size has been roughly the same throughout the studies, which is quite remarkable in a new field — to find such consistency," she reported.

Although all have been observational studies, with no interventional studies conducted yet, "we believe that based on the evidence, physicians should certainly be considering diet as well as exercise level when they're treating patients for mental illness," said Dr. Jacka.

"Plus, from a public health perspective, governments need to be looking at public policy and health promotion, especially in the States."

Beyond Depression

Dr. Fernando Gómez-Pinilla

Fernando Gómez-Pinilla, PhD, agrees that this finding is particularly important for the United States because Americans tend to consume more TFAs than populations in other countries.

"Clinicians should instruct patients about the importance of diet and maybe even educate them about what they should and shouldn't eat," Dr. Gómez-Pinilla, a professor in the Department of Neurosurgery at the University of California, Los Angeles, and part of the UCLA Brain Injury Research Center, told Medscape Medical News.

Dr. Gómez-Pinilla said his center has been looking at the effect of diet on specific brain mechanisms in several animal models.

The results of this study are important, and I think people should be more aware that the risk factors of diet can also apply across several neurological disorders beyond depression.

"I think the results of this study are important, and I think people should be more aware that the risk factors of diet can also apply across several neurological disorders beyond depression.

"For example, type of diet can be a factor in the healing process of traumatic brain injuries. The overall application for psychiatrists, in terms of these types of findings, is just very exciting," said Dr. Gómez-Pinilla.

The study was funded by the Spanish Government Instituto de Salud Carlos III, Fondo de Investigaciones Sanitarias, and the Navarra Regional Government. The study authors and commentators have disclosed no relevant financial relationships.

PLoS ONE. Published online January 26, 2011. Full text

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