Why a low-fat diet might not be helping your heart… unless you eat 'good fats' as well



00:12 GMT, 4 July 2012

Warning: A low-fat diet may only protect you against heart disease if you also eat 'good fats', a study has found

Warning: A low-fat diet may only protect you against heart disease if you also eat 'good fats', a study has found

If you've carefully been avoiding fatty foods to take care of your heart, here’s a word of warning.

A low-fat diet may not protect against heart disease unless you eat ‘good fats’ too, a study has found.

In one of the largest studies of heart disease ever, scientists at the University of Cambridge examined the diets of 25,000 Britons aged between 40 and 79.

They found those who ate foods rich in omega 6 – a fatty acid present in vegetable oils, nuts and seeds – significantly reduced their risk of heart problems.

But those who had simply cut their intake of unhealthy saturated fat did not reduce their risk to the same extent.

The researchers suggest the ‘balance of fats’ in our diets could be the key to preventing coronary heart disease, which is the UK’s biggest killer.

They say the current advice to reduce saturated fat in our diets is right, but ‘inconsistent’, because it does not tell people what to replace it with.

In the study, those at the highest risk of heart disease – who ate a lot of saturated fat and little omega 6 – were around 50 per cent more likely to suffer from it than those at lowest risk. This was regardless of other major risk factors such as obesity and smoking.

The researchers took blood samples from the volunteers in the mid-1990s, then followed them up over an average of 13 years, looking at the fats in their bloodstream compared with heart disease sufferers.

Professor Kay-Tee Khaw, lead author of the study, said: ‘It is not as simple as fat is bad for heart disease.

‘We found you have to replace saturated fat with polyunsaturated fatty acids to reduce the risk.

‘We measured 20 types of fatty acid in the blood, which was not possible to do in the past, to get a much more accurate picture of people’s diets.

‘We did find an association between coronary heart disease with certain fatty acids, but the association was much stronger when we looked at the relationship between different fats.’

Saturated fats are found in foods such as cheese

Foods like avocados contain good fats

Balancing act: Dieters are encouraged to cut out saturated fats contained in foods such as cheese, but are often not told to replace them with good fats, which can be found in avocados, eggs and poultry

Saturated fats are found in foods such as cheese, cakes and biscuits. Too much can raise cholesterol levels in the blood, which increases the risk of heart disease.

The NHS recommends a man should eat no more than 30g a day and a woman no more than 20g.

Most of us eat around 20 per cent too much. Professor Khaw said their results ‘add to the accumulating evidence’ that substituting saturated fat with omega 6 benefits the heart.

It is found in avocados, eggs and poultry as well as sunflower and corn oil.

In the study, published today in the journal PLoS Medicine, the professor added that there was potential to learn a lot more about how genetic factors affect the way different fats are metabolised.

Other fats – such as omega 3, found in fish oils, and monounsaturated fat, found in olive oil – did not appear to affect coronary heart disease, but are widely thought to be good for other conditions.

A Department of Heath spokesman said: The link between saturated fat, cholesterol and heart disease is already well established.

‘This study supports current public health advice to reduce saturated fat intake.’