Switching from fats to cooking oils may not be enough to protect the heart, researchers warned today.
Government advice to reduce the risk of heart disease is to limit intake of saturated animal fats and focus on "healthier" omega-6 fatty acids – a form of polyunsaturated fat including linoleic acid, found in safflower oil and vegetable oils.
"This advice has caused some controversy because evidence that linoleic acid lowers the risk of cardiovascular disease is limited," says Professor Philip Calder of Southampton General Hospital, UK, in response to a new study published in the British Medical Journal today.
The study looks at the effectiveness of replacing saturated fat with safflower oil, for the prevention of coronary heart disease and death. It involved 458 men aged 30-59 years with a recent coronary event living in Australia.
Those consuming safflower oil had significantly higher rates of death than those who made no change to their diet (18% versus 12%). They also had more cardiovascular disease (17% versus 11%) and coronary heart disease (16% versus 10%).
The researchers, led by Dr Christopher Ramsden of the National Institutes of Health, Maryland, USA, say: "Advice to substitute polyunsaturated fats for saturated fats is a key component of worldwide dietary guidelines for coronary heart disease risk reduction. However, clinical benefits of the most abundant polyunsaturated fatty acid, omega 6 linoleic acid, have not been established.
"These findings could have important implications for worldwide dietary advice to substitute omega 6 linoleic acid, or polyunsaturated fats in general, for saturated fats."
Professor Calder adds that, in studies that suggest a benefit of cutting saturated and trans fatty acids while increasing omega 6 and omega 3 fatty acids, the benefit may come simply from avoiding trans fats and boosting omega 3 fats.
The British Heart Foundation said the lesson from the study was to avoid using too much oil and fat in cooking.
Victoria Taylor, of the Foundation, said: "This research highlights the need for us to further understand how different unsaturated fats affect our risk of heart disease.
"Whichever fats you use it’s important to be sparing with them. Try to grill, bake, or steam your food, rather than frying.
"Measuring out oils instead of pouring straight from the bottle is another good way of making sure you’re not overdoing it."
Ramsden, C. E. et al. Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysis. BMJ 6 February 2013 doi: 10.1136/bmj.e8707 [abstract]
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