I've written before about the dangers of omega-6 PUFAs in the diet, and how high intake of PUFAs in the Western diet may be a culprit in the significant increase in inflammatory diseases, including cardiovascular disease, type 2 diabetes, obesity, cancer, autoimmune disease, and more. (1, 2) We've known for a while now that a correlation exists between a rising intake of n-6 and increased mortality from heart disease. (3)

You may have already changed your diet back to one containing high saturated fat from butter, meat, and coconut products, much to the dismay of your doctor and perhaps even your skeptical family members. The belief that omega-6 rich vegetable oils are the "heart healthy" choice is pervasive, despite limited and controversial evidence. It can be difficult to convince others that you're not asking for a heart attack by eating saturated fat.

Now, thanks to research published last week in BMJ, an old study is shedding new light on the omega-6 fatty acids and heart health controversy. The Sydney Diet Heart Study was a randomized controlled trial conducted from 1966 to 1973, comprising 458 men aged 30-59 years with a recent coronary event, such as a heart attack. Patients were randomized to either a control diet (e.g. no change) or an intervention diet, where they were instructed to increase their omega-6 PUFA intake to 15% of calories and to reduce saturated fat intake to less than 10% calories. Participants were provided with liquid safflower oil and a safflower oil based margarine to be used instead of animal fats. (They were also given safflower oil in capsules to take as a supplement. Yikes!)

As expected, those in the treatment group had a significant lowering of total and LDL cholesterol concentrations, which the original investigators assumed would therefore lead to the prevention of cardiovascular death. However, when accounting for previously lost data, this new analysis found that the intervention group instructed to eat more linoleic acid (n-6 PUFAs) actually had a higher risk of all cause mortality, as well as a higher risk of mortality from cardiovascular disease and coronary heart disease, than the group who received no dietary instructions.

Furthermore, an updated meta-analysis of linoleic acid intervention trials included in the paper showed no evidence of cardiovascular benefit. In other words, replacing saturated fat with high omega-6 vegetable oils is likely to put you at a greater risk for heart attack, and it certainly won't provide any health benefits. It's important to note that previous analyses that suggested increasing PUFA intake reduces the risk of CVD included both omega-6 and omega-3 PUFA together; the analysis in this study analyzed the effects of omega-6 linoleic acid separately.

So why are Americans still eating diets that are so high in omega-6 vegetable oils, with almost 9% of all calories from linoleic acid alone? (PDF) Despite the many studies that show the dangers of a high omega-6 PUFA intake, the conventional medical system is still preaching outdated and inaccurate information. The American Heart Association (AHA) recommends that we all aim for at least 5 percent to 10 percent of calories from omega-6 polyunsaturated fatty acids (PUFAs), and to limit saturated fat intake to less than 7 percent of total daily calories, similar to the recommendations made in the Sydney Heart Diet study. (4)

They suggest we choose "heart healthy" oils and margarines such as canola, corn, olive, peanut, safflower, sesame, soybean, and sunflower oils. This information is coming from the professional organization whose stated mission is "to build healthier lives, free of cardiovascular diseases and stroke." But as we know by now, these guidelines are not going to protect anybody from a heart attack, and could likely put people at a greater risk for cardiovascular disease. (5)

As more evidence surfaces about the dangers of high omega-6 PUFA consumption, it will be more difficult to defend the current AHA guidelines for fat consumption that are currently promoted by conventional health professionals. It seems the tide may be turning (slowly) when it comes to dietary fat recommendations, but it will be interesting to see how the American Heart Association responds to this new study. While we wait for the policy makers and medical organizations to battle it out, I'll stick to eating butter!