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New Evidence Raises Questions About Link Between Fatty Acids and Heart Disease

Research findings do not support current guidelines, authors say

A new study raises questions about current guidelines that generally restrict the consumption of saturated fats and encourage the consumption of polyunsaturated fats to prevent heart disease. The research was published March 18 in the Annals of Internal Medicine.

An international research collaboration led by the University of Cambridge analyzed cohort studies and randomized trials on coronary risk and fatty acid intake. They found that current evidence does not support guidelines that restrict the consumption of saturated fats in order to prevent heart disease. The researchers also found insufficient support for guidelines that advocate the high consumption of polyunsaturated fats (such as omega 3 and omega 6) to reduce the risk of coronary disease.

Further, 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” — questioning the existing dietary guidelines, which focus principally on the total amount of fat from saturated or unsaturated fats rather than the food sources of the fatty acid subtypes.

Lead author Dr. Rajiv Chowdhury said: “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.”

For the meta-analysis, the researchers reviewed data from 72 studies with more than 600,000 participants in18 countries. The investigators found that total saturated fatty acid, whether measured in the diet or in the bloodstream as a biomarker, was not associated with coronary disease risk in the observational studies. Similarly, when analyzing 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.

Interestingly, the investigators found that different subtypes of circulating long-chain omega-3 and omega-6 fatty acids had different associations with coronary risk, with some evidence that circulating levels of eicosapentaenoic and docosahexaenoic acids (two main types of long-chain omega-3 polyunsaturated fatty acids), and arachidonic acid (an omega-6 fat) are each associated with lower coronary risk.

Similarly, within the saturated fatty acid “family,” the researchers found weak positive associations between circulating palmitic and stearic acids (found largely in palm oil and animal fats, respectively) and cardiovascular disease, whereas circulating margaric acid (a dairy fat) significantly reduced the risk of cardiovascular disease.

In addition, when the authors investigated the effects of omega-3 and omega-6 fatty acid supplements on reducing coronary disease in the randomized controlled trials, they did not find any significant effects — indicating a lack of benefit from these nutrients.

Professor Jeremy Pearson, Associate Medical Director at the British Heart Foundation, which helped fund the study, said: “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 judgment.”

Pearson added: “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” — which means that people should consider not only the fats in their diet, but also limiting their intake of salt and sugar, and increasing their consumption of fruits and vegetables.

Source: Medical Xpress; March 18, 2014.

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