A group of long chain polyunsaturated fatty acids are known to be important to human health. Two such fats, alpha linolenic acid (ALA, C18:3 (n-3)) and linoleic acid (LA, C18:2 (n-6)) are essential to health as they are required for correct metabolic function, but cannot be synthesised in the body. These two fats are converted to a series of longer more unsaturated fats that in turn are converted to eicosanoids, signal molecules that regulate cell function. The metabolites derived from the elongation and unsaturation of ALA and LA can also be obtained from the diet, and important dietary intermediates in the pathway include eicosapentaenoic acid (EPA, C20:5 (n-3)) and docosahexaenoic acid (DHA, C22:6 (n-3)) from fish, as well as arachidonic acid (AA, C20:4 (n-6)) from meat and gamma linolenic acid (GLA, C18:3 (n-6)) from plant oils. Evidence suggests that rather than the absolute amount of these fats, it is the ratio of the omega 6 fatty acids to the omega 3 fatty acids that are the main determinant of health.
Imbalances in the omega 6 to omega 3 fatty acid ratio cause disease, because it alters the production of cellular eicosanoid molecules. The correct ratio is not known but estimates suggest that around about 3 grams of LA are required for each gram of ALA. The typical Western diet may supply upwards of 20 grams of LA for each gram of ALA. This imbalanced ratio is thought to lead to inflammation in tissues, and this then leads to the development of disease. Imbalances in the intakes of omega 6 and omega 3 fats in the diets of breastfeeding mothers can also alter the fat content of the milk they produce, and this can then have implications for infant health. Because the essential fats are also required as structural components in brain tissue, and may be involved in facilitation correct neurotransmitter function, mothers eating a typical Western diet may detrimentally affect the brain development and health of their infants. Formula fed infants may also be affected because omega 3 fats do not store well in powder.
The ratio of omega 6 to omega 3 fatty acids in the diets of mothers has been investigated with regard the brain development of their young infants1 Fatty acid intakes during the last three months of pregnancy were estimated and then the child’s neurodevelopment was assessed through its language skills at 2 and 3 years. In infants fed formula milk, those with the poorest language skills had mothers with the highest omega 6 to omega 3 fatty acid ratios during pregnancy. However, if mothers with a high omega 6 to omega 3 fatty acid ratio breastfed their infants, the detrimental effects on language development were not evident. This suggest that a high omega 6 to omega 3 fatty acid ratio, as found in the typical Western diet, is detrimental to language development during pregnancy, but not breastfeeding. Those mothers choosing to breastfeed had lower omega 6 to omega 3 fatty acid ratios, which may explain the ability of breastfeeding to compensate for a higher omega 6 to omega 3 ratio during pregnancy.
Dr Robert Barrington’s Nutritional Recommendation: Obtaining an omega 6 to omega 3 ratio of around 3 to 1 in the diet has been shown to lead to beneficial health consequences. This may be particularly important during pregnancy and breastfeeding, where the infant is reliant on correct nutritional support from the mother. Lowering the ratio of omega 6 to omega 3 fatty acids can be achieved by limiting vegetable oil to extra virgin olive oil, and supplementing the diet with fish and fish oils. Dietary sources of ALA can be obtained from green leafy vegetables as well as nuts such as walnuts.
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