Healthy margarine makes you depressed, olive oil brightens you up
Depression would become less common if we were all to stop using diet margarines and went over to using olive oil. This is the conclusion of an epidemiological study in which scientists at Georgia Southern University followed almost five thousand people for ten years. It looks as though the fatty acids in olive oil protect against depression, whereas the fatty acids in most 'healthy' margarines actually increase the risk of depression.
Depression & fatty acids
Depression has reached epidemic proportions in the last century, in much the same way as arthritis, rheumatism and diabetes have. According to studies, up to 10-15 percent of the Western population have symptoms of depression.
One theory says that depression is a consequence of increased consumption of polyunsaturated fatty acids such as those found in corn oil, soya oil and sunflower oil. These fatty acids go by the name of omega-6 fatty acids. The most well known of these, thanks to margarine ads, is linoleic acid. Omega-6 fatty acids are better for the heart and blood vessels than saturated fats, and that's why the food industry started to use them in more and more health foods.
The problem is that omega-6 fatty acids are the raw materials for inflammatory factors such as prostaglandins. Besides, omega-6 fatty acids drive omega-3 fatty acids out of the body. Brain cells need the omega-3 fatty acids, which you find in oily fish, to be able to function well. Both an excess of inflammatory factors and a shortage of omega-3 fatty acids are likely to contribute to depression and a whole load of other complaints.
Mono-unsaturated fatty acids, or omega-9 fatty acids, are found in olive oil. They are good for the cardiovascular system, just like omega-6 fatty acids, but don't make the body produce more inflammatory factors and don't drive omega-3 fatty acid out of the body.
The researchers used a questionnaire to find out how much saturated fat, omega-6 fatty acids and mono-unsaturated fatty acids the five thousand Americans ate each day. Then the researchers divided their subjects into tertiles (thirds). For saturated fat for example, the first tertile consisted of the 33.3 percent of the subjects who ate the least amount of saturated fats. The third tertile consisted of the 33.3 percent that ate the most saturated fat.
The researchers then tracked their subjects for ten years to see who became depressed.
The table below shows the relationship between depression and fatty acid intake. The researchers set the chance of developing depression at 1 for the first tertile.
The lower the value of p, the stronger the relationship. Where p is lower than 0.05 the relationship is statistically significant.
In men, a high intake of omega-6 fatty acids almost doubles the likelihood of becoming depressed. There is a tendency for a high omega-9 fatty acid intake to reduce the chance of depression in men, but it's not a statistically significant relationship. Among the women, however, the protective effect of a high intake of omega-9 fatty acids was statistically significant.
The take home message of this research is clear. If you replace diet margarines and other diet products based on omega-6 fatty acids with olive oil, the world starts to look brighter.
Prog Neuropsychopharmacol Biol Psychiatry. 2009 Aug 31; 33(6): 972-7.
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