A reduction in dietary saturated fatty acids has generally been acknowledged to improve cardiovascular health, but in a recently published study, no link could be established between intake levels of saturated fatty acids and a risk for cardiovascular disease.
A group of researchers from the Children's Hospital Oakland Research Institute in Oakland, California and the Departments of Nutrition and Epidemiology at Harvard School of Public Health in Boston, Massachusetts, performed a meta-analysis of prospective epidemiologic studies on saturated fatty acid intake and risk of coronary heart disease, stroke, or cardiovascular disease in general. In prospective epidemiologic studies a group of initially healthy people, a cohort, is followed over time to investigate if occurrence of disease is related to the exposure of certain factors e.g. dietary and other lifestyle factors. In a meta-analysis, results from different studies on a specific topic are collected and jointly analysed in order to reach a general conclusion based on the accumulated scientific data. Twenty-one studies matched the inclusion criteria for the current meta-analysis. Together these comprised 347,747 individuals of which some 11,000 developed any cardiovascular disease. The results of the analysis showed no significant association between high intake of saturated fatty acids and an increased risk of coronary heart disease, stroke or cardiovascular disease. Age, sex, and study quality were factors taken into account in the analysis, but they did not impact on the outcome.
The analysis was limited to prospective studies that can be used to study associations, but cannot clarify cause and effect. Nevertheless, the results from this meta-analysis are in line with the existing knowledge that only reducing the intake of saturated fatty acids is not likely to have major beneficial effects on the risk for cardiovascular disease. Previous studies including clinical trials however indicate that a reduction in cardiovascular disease risk will be obtained by replacing a major part of the dietary saturated fatty acids with polyunsaturated fatty acids, which is in agreement with the conclusions of a recent consultation paper on fats and health by the World Health Organization (WHO) and the Food and Agriculture Organization (FAO). Both findings from previous epidemiological studies and clinical trials support that substituting saturated fatty acids with polyunsaturated fatty acids is more beneficial for cardiovascular disease risk than replacing the saturated fatty acids with carbohydrates. In the current meta-analysis no conclusions could be drawn on the effects on cardiovascular disease risk of replacing saturated fatty acids with either polyunsaturated fatty acids or carbohydrates, since among the studies included in the analysis only a few addressed this hypothesis. The authors themselves acknowledge that their analysis is not suited (‘More data are needed’) to determine whether cardiovascular disease risk is likely to be influenced by the specific nutrients used to replace saturated fatty acids.
Fat is an essential component of our diet; we all need to eat certain amounts to stay in good health. But, it is not only the total amount of fat that is important, we also need to think about what kind of fats we choose to eat. In general, we should eat more of the ‘good’ unsaturated fats, including essential omega-3 polyunsaturated fatty acids and monounsaturated fatty acids and less of the ‘bad fats’, such as certain saturated fatty acids. Studies have shown that a high consumption of certain saturated fatty acids may increase the levels of ‘bad’ LDL-cholesterol in the blood, but this is not the case with all saturated fatty acids. Elevated blood levels of LDL-cholesterol is a known risk factor for cardiovascular disease.
The recommendation to persons who wish to reduce their risk of cardiovascular disease is to replace the saturated fatty acids in their diet with polyunsaturated fatty acids. It is considered that a diet with around 30% of daily energy coming from fat is consistent with good health, with a maximum of 10-11% from saturated fatty acids.
For more information:
Siri-Tarino PW, Sun Q et al. (2010). "Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease." Am J Clin Nutr. Published ahead of print on January 13, 2010; doi: 10.3945/ajcn.2009.27725
Joint FAO/WHO Expert Consultation on fats and fatty acids in human nutrition – background paper: Skeaff CM, Miller J (2009). “Dietary Fat and Coronary Heart Disease: Summary of Evidence from Prospective Cohort and Randomised Controlled Trials” Ann Nutr Metab 2009;55:173–201; doi: 10.1159/000229002