Benefits of vegetable oils cancelled by heart risk?
Scientists have raised doubts about the health benefits of some of Britain’s most widely used vegetable fats, including sunflower, corn and soya oils.
Although such oils can help to lower cholesterol levels in the body, research has shown that they may have other potentially damaging effects, especially on the heart, that can cancel out these benefits.
All have high levels of so-called omega-6 fatty acids. They are widely used as cooking oil, in margarines and as ingredients in processed foods such as ready meals, bread and snack foods.
The new finding could force a rethink on dietary advice, with the focus shifting more to omega-3 oils and fats, such as fish and flaxseed oils
The new finding could force a rethink on dietary advice, with the focus shifting more to omega-3 fats, such as fish and flaxseed oils, which are more expensive but have undisputed benefits to heart health.
Dr Chris Ramsden, a clinical investigator at the National Institutes of Health, in the US, led the research. He said he had assessed data on the diets and relative health of about 10,000 people over years and decades.
He said: “Our study found that there was a 13% increase in the risk of coronary heart disease and a 16% increase in the risk of early death for people eating diets high in omega-6 and low in omega-3.
“These results sound dramatic, but need to be treated with caution because there is a degree of statistical uncertainty in any such study. What we can say is there appears to be no benefit from eating a diet high in omega-6 vegetable fats, and there is a possibility of harm.”
If further evidence supports the finding, it would have a big impact on the food industry, which has heavily marketed products made with omega-6 oils on the back of studies suggesting health benefits. The American Heart Association has recommended people increase their intake of such oils.
Ramsden says that some vegetable fats remain preferable to trans fats, and are possibly better than saturated animal fats. Both these latter groups are known to raise blood cholesterol levels; over years, this can raise the risk of heart disease.
Both omega-6 and omega-3 fatty acids comprise a chain of about 18-22 carbon atoms, but differ in the location of a rigid “double bond” between two of the atoms. This apparently tiny difference has a great effect on how they behave in the body.
Philip Calder, professor of nutritional immunology at the University of Southampton and editor of the British Journal of Nutrition, which published Ramsden’s paper, said humans had not evolved to cope with the high levels of omega-6 fats now found in western diets.
He said: “The fats we eat are used to build cell membranes and are very important in organs like the brain and heart. Omega-6 fats behave differently in the body than omega-3. They can cause inflammation and over years that may lead to health problems.”
Jack Winkler, professor of nutrition policy at London Metropolitan University, said: “This research is extremely important because it could lead to a reversal in the advice we give consumers about dietary fats and heart disease.”