Fish has traditionally been called brain food, and for good reason. Fatty cold water fish such as tuna, mackerel, salmon, pilchards and trout accumulate long chain fatty acids in their skin, belly cavity and flesh. These oils have a low melting temperature and are therefore beneficial compared to shorter more saturated fats in the cold environment of these fish because they remain liquid. These oils are similar in composition to those found in the livers of white fish such as haddock and cod. Fish oils contain the long chain fatty acids eicosapentaenoic acid (EPA, C20:5 (n-3)) and docosahexaenoic acid (DHA, C22:6 (n-3)) which have been shown to have beneficial health effects in humans, particularly against cardiovascular disease. Humans possess high concentrations of DHA in the central nervous system and as a result the maternal intake of DHA during pregnancy and lactation, and the subsequent intake of this fatty acid through childhood, may influence the development of the central nervous system.
Studies have investigated the cognitive benefits of taking fish oils, particularly in infants and the young. For example, in one study, researchers evaluated the cognitive effects of DHA, as well as another long chain fatty acid, arachidonic acid (AA, C20:4 (n-6))1. The intakes of DHA and AA were 0.32, 0.64, or 0.96 % and 0.64 % of total fatty acids, respectively. The study was designed so that the children consumed variable amounts of the three fatty acids from birth (initially via an infant formula) to 6 years of age. The results showed that by 18 months of age the supplementation did not have any effect of cognition in terms of a number of standardised language and performance tests selected. However, when the children reached 3 to 5 years of age, positive effects of both DHA supplemented groups were evident in several measures of cognition. Therefore supplementation with long chain fatty acids from fish oil appears to provide beneficial learning effects in young human subjects.
Technically DHA and EPA are not essential fatty acids as they can be synthesised in humans from the essential fatty acid precursor alpha linolenic acid (ALA, C18:3 (n-3)). However, this conversion is not efficient for a number of reasons, the most researched of which is the low activity of the delta 6-desaturase rate limiting step. As a result under condition of stress such as exercise, or during periods of rapid growth, preformed DHA and EPA are required to maintain correct metabolic regulation through eicosanoid formation. The long chain fatty acids DHA and EPA therefore fall into the category of conditionally essential nutrients. Because the central nervous system of the young has a high requirement for DHA, low intakes may prevent full development and stifle cognition. It appears that although this effect may not be evident in early life, the full extent of a long-term DHA insufficiency may manifest itself fully in later years.
Dr Robert Barrington’s Nutritional Recommendation: The fish oils EPA and DHA are conditionally essential fatty acids in humans. Both appear to have beneficial effects against cardiovascular disease and this may relate to their ability to modulate the inflammatory reaction in cells of the arteries as well as increase the oxidation of other fatty acids. However, DHA also appear to have beneficial cognitive effect, particularly during the development of the central nervous system. Maternal intakes of DHA are therefore pivotal in dictating the cognitive outcomes of the offspring, although this effect may not be evident for some time into the child’s life.
RdB
