A article published in the latest edition of the American Journal of Clinical Nutrition reports areas of consensus reached by 17 scientists from around the world, who took part in a symposium held at the University of Copenhagen in Denmark last year, chaired by Arne Astrup of the university’s Department of Human Nutrition and Walter Willet, of the Harvard School of Public Health’s Department of Nutrition in Boston, Massachusetts.
They said that most dietary recommendations aim to reduce saturated fatty acid intake to less than ten percent of total energy but do not specify the replacement macronutrient. In Western dietary patterns, when people try to reduce saturated fatty acid (SFA) consumption, the replacement often tends to be carbohydrates – and often refined carbohydrates – but polyunsaturated fatty acids (PUFAs) are currently the only macronutrient with strong evidence for coronary heart disease (CHD) risk reduction when replacing SFAs, the authors said.
“The totality of evidence indicates that substituting PUFAs for SFAs is beneficial for lowering total and LDL cholesterol [low-density lipoprotein, or so-called ‘bad’ cholesterol] and for CHD prevention, but there is no evidence to support the benefit of substituting refined carbohydrates for SFAs,” they wrote.
Food before nutrients
They said that food based recommendations are more useful than nutrient based advice but there is limited evidence linking specific foods or diets with cardiovascular disease risk. In particular, they said that there is strong evidence that diets high in processed meats are linked to an increased risk of heart disease, but there is “no consistent evidence” that a high intake of dairy products is associated with heart disease.
“There is increasing evidence to support that the total matrix of a food is more important than just its fatty acid content when predicting the effect of a food on CHD risk, eg, the effect of SFAs from cheese on blood lipids and CHD may be counterbalanced by the content of protein, calcium, or other components in cheese,” they wrote.
Some randomized controlled trials have provided evidence that substituting PUFAs for SFAs could reduce risk of coronary heart disease (CHD), but no benefits have been found for substituting carbohydrates for SFAs. However, the authors noted that the quality of the carbohydrates was not addressed.
They added that there is insufficient evidence to support the benefit of substituting monounsaturated fatty acids (MUFAs) for SFAs, mainly because of confounding factors, including the fact that dairy and meat are significant sources of MUFAs in the typical Western diet.
It has also been suggested that different saturated fatty acids may have different physiological effects, but the authors said it is not feasible to separate different saturated fats in terms of food choices, because foods tend to contain a combination.
“We do not yet have enough evidence to give dietary recommendations for individual SFAs, but the evidence is useful for advising food manufacturers, eg, stearic acid can be used as a replacement for trans fatty acids where appropriate, although the evidence is not sufficient to determine whether it is superior to other SFAs because multiple pathways may be involved and clear data on clinical endpoints are not available.”
Source: American Journal of Clinical Nutrition
2011; Vol. 93, pp. 684–8
“Perspective: The role of reducing intakes of saturated fat in the prevention of cardiovascular disease: where does the evidence stand in 2010?”
Authors: Arne Astrup, Jørn Dyerberg, Peter Elwood, Kjeld Hermansen, Frank B Hu, Marianne Uhre Jakobsen, Frans J Kok, Ronald M Krauss, Jean Michel Lecerf, Philippe LeGrand, Paul Nestel, Ulf Rise´rus, Tom Sanders, Andrew Sinclair, Steen Stender, Tine Tholstrup, and Walter C Willett