Essential dietary components are those required by the body to maintain health, but which cannot be synthesised endogenously. Vitamins and minerals are the most well known essential elements, but there are also a number of amino acids and fatty acids that are essential to health. The two fatty acids required for health are alpha-linolenic acids (ALA, C18:3 (n-3)) and linoleic acid (LA, C18:2 (n-3)), polyunsaturated fatty acids belonging to the omega 3 and omega 6 families, respectively. These fatty acids are converted in the body to a number of short-lived hormones called eicosanoids that regulate cell function and the inflammatory response. The typical Western diet supplies too much LA and too little ALA and this causes an imbalance to occur in eicosanoid formation, with the result that cell regulation and the control of inflammation becomes dysfunctional. The current recommendation is therefore to limit intakes of vegetable oils containing LA and increase consumption of oils containing ALA. However, this may not provide the desired health benefits.
Because most humans have a genetic defect in the gene that produces one of the ALA to eicosanoid enzymes, conversion of preformed ALA to omega-3 eicosanoids is not efficient in humans. Consumption of ALA might not therefore have beneficial effects in some individuals. The solution to this may be consumption of fatty fish which contain eicosapentaenoic acid (EPA, C20:5 (n-3)) and docosahexaenoic acid (DHA, C22:6 (n-3)), both of which are intermediate chemicals in the ALA to eicosanoid pathway and both of which can therefore increase production of omega-3 eicosanoids in the absence of adequate ALA conversion. These fatty acids may therefore be considered conditionally essential to health, and evidence suggests that DHA in particular is essential to infant health as it is also required to allow correct growth and maturation of the central nervous system during pregnancy and in the early stages of infancy. In this respect the diet of the mother is particularly important and must contain adequate preformed DHA.
Studies have shown that maternal diet during the pre- and postnatal period is paramount in allowing the correct development of the brain of the infant. Because the brain is composed mainly of lipids, the fatty acid content of the maternal diet is important as this will influence the content of the milk. For example, in one study1, researchers assessed the ability of DHA in the diet to increase the DHA content of milk. Lactating women were fed fish oil supplements containing 11 % DHA with one group of women receiving 5 grams per day for 28 days, one group receiving 10 grams per day for 14 days and one group received 47 grams per day for 8 days. Each dose of fish oils produced a dose dependent increase in the DHA content of the milk from 0.1 % at baseline to 0.5 in the 5 grams per day group, to 0.8 in the 10 grams per day group and to 4.8 % in the 47 grams per day group. The plasma DHA content of the mothers also increase in a dose response manner reflecting the dietary intake of DHA.
Therefore these results suggest that dietary DHA is effective at raising the plasma and milk levels of DHA in lactating women. This is of paramount importance because the preformed DHA is required for correct central nervous system formation and function in infants. Current recommendation are to consume more fish because of the omega-3 fatty acids it contains, but pregnant and nursing mothers are advised not to consume large fatty cold water fish more than a few times per month because of the high levels of pollution it contains. In this study the women were fed fish oil capsules and there is no indication as to the pollution levels were in the capsules or indeed if the capsules had been treated to remove the pollution. However, unless the pollution is removed it will remain in the oil and be transferred to the capsules. Treated capsules are available and if fish oils are to be consumed this is a viable alternative for nursing and pregnant mothers. Alternatively, DHA supplements are available from algae that is free from pollution.
Dr Robert Barrington’s Nutritional Advice: Large cold water fish are polluted and so should not be consumed during pregnancy and breastfeeding. Smaller coldwater fish such as mackerel may be less polluted and safer. Preformed DHA from algae in capsules may the the best way of obtaining DHA in this regard as it is grown in tanks free from pollution is tightly controlled conditions.
RdB
