One serving of depression with Mayo, please

18. March 2011
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Dietary fats affect not only physical, but also mental health. Data show that unhealthy fats like trans fats significantly increase the risk of depression. Unsaturated fatty acids have, however, neuroprotective effects.

Much of what has a traditional place on the lunch or dinner table in the Mediterranean is actually medicine – this is now indisputed and has achieved scientific consensus. Numerous studies have conclusively demonstrated that the Mediterranean diet has extensive health-promoting benefits. In view of this, it is officially – including by the World Health Organisation (WHO) – recommended for prevention of and as supportive therapy against cardiovascular diseases. But the list of indications for a shift to a Mediterranean diet is even longer. Some of these It includes type II diabetes, obesity, gastrointestinal disorders, and tumors. Now there is another disease to be added: depression. This is because the risk of developing it is significantly influenced by the Mediterranean diet: It protects not only the heart and blood vessels, but also the mind. This effect is attributable primarily to the types of fat consumed.

Striking North-South Divide

According to data from epidemiological studies, about six million German adults are affected by depression. Among the member states of the EU, there are twenty million people affected per year. In addition there are clear differences between northern and southern European countries. In northern Europe depression occurs much more commonly than in the southern EU countries. Thus, the European residents of the Mediterranean enjoy better overall mental health than residents of the Scandinavian countries, who are leading the way in the opposite respect. Without doubt, UV radiation is a major factor. But the striking North-South divide results not only from fewer or more hours of sunshine. It’s also due to culinary habits that the psychological state in more northern latitudes is more poorly composed. What is now confirmed in a large-scale study by Spanish scientists is that the risk of mental illness is one we ‘serve ourselves’.

“Food keeps body and soul together …”

The so-called “Sun Project” has delivered evidence in favour of a particular view for the first time: mental health, and especially the incidence of depression, is also dependent on diet. This is a relationship which has been discussed and suspected for some time. Already in September 2009 such a study came to the conclusion that the Mediterranean diet lowers the risk of being a sufferer of depression. Researchers from the University of Navarra and Las Palmas / Gran Canaria in that instance did not attribute it to a particular nutrient. Rather, it was assumed that the synergy of several potentially health-promoting substances is the cause of the neuroprotective effect. This effect is based, however, as the group led by Dr. Almudena Sánchez-Villegas has now revealed, on the type of fats consumed: “A direct relationship does actually exist between the intake of different fatty acids and the occurrence of depression,” asserts Dr. Sánchez -Villegas.

In the Sun Project carried out by her team, 12 059 university students – 5038 men and 7021women – from all over Spain were included. The prospective cohort study started in 1999 and was completed in late 2010. At its outset, none of the subjects – with a current average age of 37.5 years – suffered from depression. The dietary habits of the Sun Project participants were regularly collected by mail via 136-point comprehensive surveys. Prominent matters were the frequency and quantity of meat and meat products, fish, milk and milk products, vegetables and fruit, nuts and grain products and alcohol. In this way, the consumption of fatty acids could be differentially analysed : “We explicitly recorded the intake of saturated fats, trans fats, simple and polyunsaturated fatty acids,” says Dr. Sánchez-Villegas. In follow-up tests, the subjects were tested for depression. After 6.1 years a median of 657 new cases turned up.

Trans Fats: greatest risk factor

The findings from the Sun Project dramatically confirm a long-held thesis: The increasing consumption of trans fats and saturated fatty acids and the declining supply of unsaturated fatty acids has a negative impact not only on physical health. The psyche is also threatened.

The highest danger in this context comes from trans fat (TFA, trans unsaturated fatty acids). Found especially in chips, french fries, baked products and industrial ready-to-eat meals, these turned out to be a significant risk factor. According to Dr. Sánchez-Villegas, they heighten the risk of depression by a notable 48 percent (p = 0.003). This worrying trend is likely to be more pronounced in other countries, according to the researchers from Navarra and Las Palmas. Most notably in the U.S., as the calorie intake of trans fat is 2.5 percent in their case. In Spain, however, trans fats account for only 0.4 percent of the 36.7 percent of total calories from fat.

Cardioprotective = neuroprotective

Monounsaturated and polyunsaturated fatty acids have a positive effect on mental health. Their influence was examined by the team under Dr. Sánchez-Villegas as well. According to her, a dose-dependent inverse relationship was found between the intake of monounsaturated (p = 0.053) and polyunsaturated fatty acids (p = 0.031) and the occurrence of depression. The same is true for omega-3 and omega-6 fatty acids. Olive oil also proved to be neuroprotective (p = 0.030) – which is, according to Dr. Sánchez-Villegas, due to its anti-inflammatory and antioxidant properties. “Our results show,” says the Spaniard, “that the relationships between different types of fat and depression are comparable to those between cardiovascular disease and dietary fat”.

Radioprotective is consequently neuroprotective. This could be due to substances that are also relevant in cardiovascular diseases. The initiators of the Sun Project refer here to, among other things, pro-inflammatory cytokines that modify the metabolism of neurotransmitters and inhibit the expression of brain-derived neurotrophic-factor. This growth factor – abbreviated as BDN – might strike the connections in neuroprotection. It is influenced, according to Dr. Sánchez-Villegas, by the endothelial production of BDNF: “People with depression have decreased BDNF levels in comparison to healthy people and antidepressants could increase it.” A profile of fatty acids, which improves the endothelial functions, could accordingly also protect against neuropsychological disease, suspect those in the Sun Project.

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