Evidence suggests that omega 3 (n-3) fatty acids are protective of cardiovascular disease. The reason for this is not fully understood, but may relate to the metabolism of omega 3 fatty acids to cellular signal molecules that can regulate inflammation. This is relevant because research consistently shows that inflammation is involved in the aetiology of cardiovascular disease. The association between higher intakes of omega 3 fatty acids and cardiovascular disease has been well researched in the nutritional literature, with evidence generally supporting the contention that omega 3 fatty acids are cardioprotective. For example, in a study published in 2013, researchers investigated the association between omega 3 fatty acid intake and the rate of progression of carotid intima media thickness in Finnish adults1. The results of the study showed that the growth of the carotid intima media wall, a possible marker for atherosclerosis, was inversely associated with the intake of omega 3 fatty acids in the diet, as well as plasma levels of omega 3 fatty acids.
Therefore those subjects with the highest intakes of omega fatty acids had the slowest progression of thickening of their carotid artery wall. However, this association for omega 3 fatty acids was only present in those subjects who were low birth weight preterm infants. In subject who had undergone a full term pregnancy and had a normal birth weight, the inverse association between omega 3 fatty acids and rate of intima media thickening was not significant. This likely relates to the increased risk of cardiovascular disease in individuals who have impaired foetal growth. For example, studies have estimated that every 1 kg decrease in birth weight is associated with a 10 to 20 % increase in the risk of ischaemic heart disease. These results suggest that higher intakes of omega 3 fatty acids may be able to protect against this increased risk in those with foetal growth defects. This is significant because it has been estimated that 12 % of births in the United States each year fall into this category.
Another way of interpreting these results is that a certain sub-group of the population has a higher requirement for omega 3 fatty acids. During foetal growth, these individuals do not receive adequate omega 3 nutrition and this causes them to be underweight and premature. During adult life these individuals continue to require higher intakes of omega fatty acids, and those that do not have a much higher risk of developing cardiovascular disease. It would have been interesting if the researchers had measured the presence of omega 3 fatty acid deficiency symptoms on the subjects such as dry skin and eczema to assess their requirements for omega 3 fatty acids. In fact the same authors did show that supplementation of omega 3 fatty acids to low birth weight preterm children at between 6 months and 5 years of age did attenuate the significance of the association by age 8 years2. This has implications for other studies investigating the effects of omega 3 fatty acids on cardiovascular disease, because the effects may be modified by birth status in the subjects.
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