During the past several decades, reduction in fat intake has been the main focus of dietary recommendations to decrease the risk of chronic diseases, including coronary heart disease. However, several lines of evidence indicate that the quality of dietary fat has a more important role in reducing risk than the total amount of dietary fat. Metabolic studies have clearly established that replacing saturated and trans fatty acids with cis-unsaturated fatty acids has the most favourable effect on plasma total and LDL cholesterol levels, and that reducing the total amount of fat can reduce HDL cholesterol and increase fasting TG levels. Results from epidemiological studies and controlled clinical trials show that replacing saturated and trans fatty acids with c/s-unsaturated fatty acids is more effective in lowering risk of CHD than reducing total fat consumption. There is still no consensus on whether the total amount of dietary fat increases body weight in the long term and in this way offsets favourable effects of high unsaturated fat diets. In any case, the evidence favouring low-fat diets to prevent CHD is not convincing. Nevertheless, diets high in fat are often also high in energy. Therefore, it seems prudent to limit the total intake of fat, in particular for people who are not physically active and for those who experience weight gain.
The different specific saturated fatty acids can differ in their effect on blood lipid levels. In particular, stearic acid does not raise cholesterol levels as much as other saturated fatty acids. However, the implications for the risk of coronary heart disease are unclear. Because of the growing interest in stearic acid as a substitute for trans fatty acids to add texture and solidity in foods, there is a need to assess the effects of this fatty acid on cardiovascular disease end-points and risk factors beyond blood lipids and lipoproteins. Different types of TFA in the diet probably have similar detrimental effects on health, and there do not seem to be compelling reasons to discriminate between these.
Modern dietary recommendations agree on the need to set limits for the intake of total fat, saturated fatty acids, and trans fatty acids. In setting the limits for total fat, the optimal intakes rather than the maximal intakes to prevent chronic diseases are increasingly taken into account. There is good agreement on the limits set. Most recommendations for Europe and North America advise that total fat intakes should be in the range of 20-35 energy %. In addition, all recommendations stress the importance of maintaining energy balance to prevent weight gain. Saturated fat intake should be less than 10 energy % (ca 20g/day)), and TFA intake should be less than 1 or 2 energy % (2-4g/day). Although intakes of saturated fat and trans fat should both be decreased, saturated fat should be the primary focus of dietary modification, because saturated fat consumption is proportionately much larger than that of TFA.
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