The role of dietary fats for preventing cardiovascular disease. A review.

ABSTRACT

At the present, there is a pandemic of chronic non-communicable disease (NCD) affecting most countries of the world. The World Health Organisation (WHO) has identified the main contributing determinants to be cardiovascular disease (CVD), diabetes, malignant cancer and chronic disease of the respiratory system. Unhealthy nutrition, as well as other adverse lifestyle health behaviour are recognised to be part of the prime factors responsible. According to WHO guidelines, a healthy lifestyle should include substituting saturated fatty acids (SFAs) with polyunsaturated fatty acids (PUFAs) together with eliminating trans-fatty acids from the diet and limiting the intake of refined carbohydrates in conjunction with increasing the consumption of fruit, vegetables, nuts and wholegrain cereal products. Recent studies on the relations between CVD prevention and dietary fats have been however unclear. The present study thus aims to provide a review of current evidence and opinion on the type of dietary fat most appropriate for preventing arteriosclerosis. The adoption of dated recommendations on the need to increase dietary PUFA in both Northern Europe and America has led to n-6 PUFAs being predominant in diets as compared to n-3 PUFAs. This disproportion may have caused mortality to rise, due to CVD, as a result of arteriosclerosis in these countries. In contrast, a traditional Mediterranean diet yields a PUFA n-6/n-3 ratio of 21, which is much lower than for the aforementioned northern countries. Some authors however consider that assessing this ratio is irrelevant and that decreasing n-6 PUFA may be harmful. Such differences of opinion leads to confusion in adopting an effective approach for arteriosclerosis management regarding dietary n-6/n-3 ratios. Moreover, recent studies have added much controversy to the notion that the characteristics of SFAs are responsible for arteriosclerosis. These found that replacing dietary SFAs with carbohydrates did not reduce the risk of ishaemic heart disease (IHD). Furthermore, changing to monounsaturated fatty acids (MUFAs) gave equivocal findings, but only changing to PUFAs reduced the risk of IHD. This last statement however requires qualification in that dietary n-6 PUFAs increases the risk of IHD. It is only the n-3 PUFAs that are beneficial. Up till now these controversies remain unsolved. It is however noteworthy that adopting a Mediterranean diet reduces IHD mortality. This is explained by a low consumption of SFAs but high intake of unsaturated fatty acids including n-3 PUFAs, and is linked to choosing the right vegetable fats. Oils that contain alpha-linoleic acid (ALA) are to be preferred in the diets of northern countries.