Anxiety and related brain disorders are incredibly complex to study as they are to some extent subjective, and also modified by a number of other factors. Whether it is even possible to define anxiety would be debatable, based on the overlapping and wide spectrum of different anxiety behaviours characterised. In general, anxiety disorder is characterised by an often irrational fear or anxiety that may be idiopathic in nature. This can lead to withdrawal and stress. That being said, a broad definition of anxiety and related behaviors has been proposed, and animals models have been used to study the effects of nutrition on these behaviours. One line of nutritional researcher has focussed on the alteration of brain function through nutritional intake of fats. In particular, researchers have studied the way that the essential fatty acids, alpha linolenic acid (ALA, C18:3 (n-3)) and linoleic acid (LA, C18:2 (n-6)), and changes to the ratio of their intakes, can alter the chemistry of the brain and affect the susceptibility to anxiety related disorders.
Essential fats are important to brain function, because their metabolites are incorporated into cell membranes and here they regulate cell function, including the firing of nerve impulses that dictate brain function. Essential fats are required in a particular ratio in the diet in order to maintain the delicate biochemistry of the cells they govern and deviations from this ratio can alter cell function. In the case of brain cell function, this may change the way brain cells operate and this may in turn lead to pathologies such as anxiety. Animal models are useful for the study of nutritional influences on brain function as the animals tend to be more homogeneous in their core behaviours compared to humans. In this regard, the effects of altering the essential fatty acid intake of pigs has been investigated in order to understand how this influences the anxiety behavioural characteristics of the pigs. In one study pigs were fed 4 different essential fatty acid diets and their anxiety behaviour was monitored to ascertain the influence of the diets1
Low LA acid diets increased the time spent on exploration, particularly nosing in the pen and open field. This increase in nosing reduced the time the pigs spent lying with open eye in the pen. A high intake of both LA and ALA and a low LA and high ALA intake decreased the time taken for the pigs to explore a new object introduced into their pen compared to a low LA and low ALA intake. Medical examination of the pigs showed that high docosahexaenoic acid (DHA, C22:6 (n-3)), a metabolite of ALA, was positively correlated with explorative behavior, whereas arachidonic acid (AA, C20:4 (n-6)), a metabolite of LA, was negatively associated with exploratory activity. These results suggest that higher intakes of ALA compared with LA may be beneficial with regard reducing anxiety in pigs. The fact that LA intakes are too high in the Western diet, and ALA too low, may suggest that the consumption of the typical Western diet could exacerbate the risk of developing anxiety related disorders in humans.
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