Fats and heart disease: Guidelines questioned
18th March 2014 -– New research, led by the University of Cambridge, questions current guidelines which encourage a diet low in saturated fats and high in polyunsaturates, in order to reduce the risk of coronary heart disease.
Dr Rajiv Chowdhury, lead author of the research, says in a press statement: "These are interesting results that potentially stimulate new lines of scientific inquiry and encourage careful reappraisal of our current nutritional guidelines.
"Cardiovascular disease, in which the principal manifestation is coronary heart disease, remains the single leading cause of death and disability worldwide. In 2008, more than 17 million people died from a cardiovascular cause globally. With so many affected by this illness, it is critical to have appropriate prevention guidelines which are informed by the best available scientific evidence."
Just last week, a leading US cardiovascular research scientist wrote an editorial in the BMJ's open access journal, Open Heart, in which he argued that current dietary advice, to replace saturated fats with carbohydrates or omega 6-rich polyunsaturated fats, is based on flawed and incomplete data from the 1950s.
For this latest study, international researchers analysed data from existing studies and randomised trials on coronary risk and fatty acid intake.
They found that total saturated fatty acid, whether measured in the diet or in the bloodstream, was not associated with coronary disease risk in the observational studies.
Similarly, when analysing the studies that involved assessments of the consumption of total monounsaturated fatty acids, long-chain omega-3 and omega-6 polyunsaturated fatty acids, there were no significant associations between consumption and cardiovascular risk.
Furthermore, when specific fatty acid subtypes, such as different types of omega 3, were examined, the effects of the fatty acids on cardiovascular risk varied even within the same broad 'family'. This brings into question the existing dietary guidelines that focus principally on the total amount of fat from saturated or unsaturated fats rather than the foods they come from.
Within the 'family' of saturated fatty acids, the researchers found weak positive associations between circulating palmitic and stearic acids (found especially in palm oil and animal fats respectively) and cardiovascular disease, whereas circulating margaric acid (a dairy fat) significantly reduced the risk of cardiovascular disease.
Professor Jeremy Pearson, associate medical director at the British Heart Foundation, which helped fund the study, says in a prepared statement: "This analysis of existing data suggests there isn't enough evidence to say that a diet rich in polyunsaturated fats but low in saturated fats reduces the risk of cardiovascular disease. But large scale clinical studies are needed, as these researchers recommend, before making a conclusive judgement.
"Alongside taking any necessary medication, the best way to stay heart healthy is to stop smoking, stay active, and ensure our whole diet is healthy – and this means considering not only the fats in our diet but also our intake of salt, sugar and fruit and vegetables."
The research has been published in the 18th March edition of Annals of Internal Medicine.