A new study published in the journal Circulation found that eating vegetable oils rich in alpha-linolenic acid (ALA) was linked with a clearly lower risk of non-fatal heart attacks.
ALA is a medium-length polyunsaturated omega-3 fatty acid. It is often overlooked in favour of the long-chain omega-3s EPA and DHA, found in fish oils. ALA intake has grown in recent decades through vegetable oils such as soybean oil and flaxseed (linseed) oil.
"Eating vegetable oils that contain ALA could have an important impact on heart disease in countries where people eat little fish, or where omega-3 sources are scarce because people cook with sunflower and corn oil," says Dr Hannia Campos.
The study included 1,819 people who had survived a heart attack and 1,817 matched controls. Fat tissue samples were taken to measure the fatty acids stored there. ALA in fat tissue ranged from 0.36% to 1.04%, and average intake from 1.11 to 2.35 g a day.
After allowing for smoking, exercise, diabetes, blood pressure, fat intake and waist-to-hip ratio, there was an inverse link between ALA (in fat tissue and in the diet) and the risk of heart attack: from the lowest to the highest tenth, the relative risk fell to about 0.4. But the relationship wasn't a straight line: the benefit rose until ALA in fat tissue reached about 0.7%, equal to eating about 1.8 g of ALA a day, with no extra protection above that.
So moderate amounts of ALA bring the benefit: about half a teaspoon of flaxseed oil, or one or two tablespoons of soybean oil a day, which can be added to salads to protect the heart.
In another study, published in Hypertension, Japanese researchers found an inverse link between linoleic acid intake and blood pressure: 9 g a day was linked with blood pressure lower by 1.4 mmHg (systolic) and 0.9 mmHg (diastolic).
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