It is almost impossible to find a doctor who will not recommend that if we want to reduce our risk of cardiovascular disease and death from heart attack, we should try to eliminate as many saturated fats from our diet as possible and instead substitute them with polyunsaturated fats such as those found in most vegetable oils. However, a recent study published in the British Medical Journal (BMJ) has found that this advice may be highly flawed.
For over 50 years, physicians have advised people to cut out the butter and lard that was a staple in every home in our grandmothers’ day, which they used for cooking everything from roast chicken to apple pie. Doctors have believed that reducing our intake of saturated fat would reduce our cholesterol levels and lessen our risk of heart disease. However, saturated fat is not the culprit in high cholesterol, as recent studies have shown, and having low levels of cholesterol does not necessarily mean you have a lower risk of heart disease.
Re-Evaluation of the Sydney Diet Heart Study
The study in the BMJ was a meta-analysis of missing data recovered from the Sydney Diet Heart Study, which had been conducted between 1966 and 1973. For three years, researchers followed 458 Australian men who had a history of cardiovascular disease. The men were randomized into two groups, one of which was instructed to reduce their intake of saturated fats to 10% of calories consumed and increase their intake of polyunsaturated fatty acids (PUFAs) in the form of safflower oil to 15% of their daily calories. The control group was not given any specific dietary advice, but all non-dietary parameters of the study participants were the same.
Dr. Christopher Ramsden, author of the study and a clinical investigator at the U.S. National Institutes of Health in Washington said, "The group that was randomized to omega-6 from safflower oil, they had increased risk of death from all causes as well as death due to coronary heart disease and death due to cardiovascular disease and this was despite significant cholesterol lowering."
Too Much Omega-6 the Culprit
In our typical Western diet, the most commonly consumed PUFA is in the form of omega-6 linoleic acid. Researchers believe that the problem with omega-6 fatty acids is that they are not only involved in lowering cholesterol, but they may also increase inflammation, oxidation and clotting, which have a more detrimental effect on cardiovascular health than any benefit that may be attained from the lowering of cholesterol.
Despite a growing body of evidence that increasing our consumption of omega-6 fatty acids actually raises our risk of heart disease (particularly in cases where intake of omega-3 fatty acids is low), the American Heart Association refuses to adapt their recommendations to reflect new research and still advises people to increase their intake of these fats.
Philip C. Calder, professor of nutritional immunology at the University of Southampton in the UK noted in an editorial about the study that it "provides important information about the impact of high intakes of omega 6 PUFAs, in particular linoleic acid, on cardiovascular mortality" and that physicians and dietary advisers should rethink the current "saturated fat bad, omega 6 PUFA good" doctrine. Calder believes that this study served to "underscore the need to properly align dietary advice and recommendations with the scientific evidence base."
How to Reduce Intake of Omega-6 Fatty Acids
It is difficult to avoid omega-6 oils, as they are used for so many of the common items we eat every day. However, if you cook for yourself you have a choice in the level of omega-6 you take in. The most common omega-6-rich oils used for cooking are corn oil, sunflower oil, safflower oil, cottonseed oil and soybean oil, including margarines made from these oils. Instead, substitute olive oil or coconut oil for cooking and try to increase your intake of omega-3 fatty acids, which will help to balance out your intake of omega-6. Omega-3 fatty acid is best found in fatty fish, such as sardines, mackerel, herring and salmon, and in flaxseed oil. Also, by reducing your intake of processed foods you can significantly cut down on the amount of omega-6 you consume, as most processed foods contain oils high in omega-6 fatty acid.