Consuming lots of red or processed meat may raise your chance of a stroke — but regularly cooking with olive oil lowers the risk, more research has suggested.
Experts who tracked 100,000 people for three decades said results confirmed diets high in fat are not the problem.
Echoing dozens of similar studies, it instead pointed the blame at the specific types of fats consumed.
They found people who ate the most lard, red or processed meat were up to 16 per cent more likely to suffer a stroke than those who ate the least.
People who got most of their fat intake from dairy, like butter and cheese, were not at an increased risk, the study found.
Those who often cooked with olive, corn and soybean oils were 12 per cent less likely to have a stroke than those who ate the least amount of these types of fat.
Lead researcher Dr Fenglei Wang, from the Harvard School of Public Health, said the findings suggest the type of fat people eat is more important for preventing a stroke than how much they eat.
Instead, fat from red and processed meats, as well as non-dairy animal fat, appear to increase the risk of stroke, while dairy and vegetable fat did not seem to increase the likelihood.
Experts have long warned that while red meat — such as beef, lamb and pork — is a good source of protein and vitamins, eating too much may also have health risks.
They believe the high amounts of saturated fat in the meat increases levels of harmful cholesterol, while salt raises blood pressure — both of which increase the risk of having a stroke.
And chemicals found in red meat — that are added during processing or produced when cooking — damage cells which can increase the risk of cancer.
The NHS recommends that adults should eat no more than an average of 70g of red or processed meat per day — equivalent to around two slices of bacon or one sausage.
There are more then 100,000 strokes in the UK and 800,000 in the US every year, leading to 38,000 and 150,000 deaths, respectively.
Experts have long warned that while red meat — such as beef, lamb and pork — is a good source of protein and vitamins, eating too much has health risks, such as increased risk of bowel cancer, as well as heart and circulatory diseases. The NHS recommends that adults should eat no more than an average of 70g of red or processed meat per day — equivalent to around two slices of bacon or one sausage
The preliminary research was presented at the American Heart Association’s (AHA) Scientific Sessions and has not yet been published in a journal.
They looked at data on 117,136 health workers in the US — with an average age of 50 — who were monitored over 27 years in two previous studies examining the risk factors for different chronic diseases.
All volunteers were healthy when they enrolled in the studies in the 1980s and every four years they provided information on the amount of fat they ate and in what form through questionnaires.
During the study, 6,189 participants suffered strokes.
Researchers did not quantify how much each group consumed. Instead, volunteers were just grouped into quintiles based on their diet.
But eating lots of animal fat from dairy sources — such as cheese, butter milk and cream — did not make it more likely for people to suffer a stroke, according to their research.
And those who ate the most vegetable and polyunsaturated fats — including olive oil, corn and soybean oils in cooking — were 12 per cent less likely to have a stroke compared to those who at the least.
Researchers argued their study is the first to comprehensively analyse how eating different types of fat affects the risk of having a stroke.
But they noted that the study is observational, so they cannot confirm a cause-and-effect link between fat consumption and stroke risk.
The latest study did not account for other factors such as lifestyle, deprivation or ethnicity.
And participants were asked about their average fat consumption over the previous year, so there may be inaccuracies in their answers, the researchers admit.
The study looked at health workers and 97 per cent were white, so the findings may not be consistent in other groups, and they did not account for other factors, such as lifestyle, deprivation and ethnicity.
Dr Wang said: ‘Our findings indicate the type of fat and different food sources of fat are more important than the total amount of dietary fat in the prevention of cardiovascular disease including stroke.’
Professor Alice Lichtenstein, a nutrition science and policy expert at Tufts University in Boston, who was not involved in the research, said many processed are high in salt and saturated fat and low in vegetable fat.
Previous studies have found replacing processed meat with other protein sources, particularly plant sources, is associated with lower death rates, she said.
Professor Lichtenstein added: ‘Key features of a heart-healthy diet pattern are to balance calorie intake with calorie needs to achieve and maintain a healthy weight, choose whole grains, lean and plant-based protein and a variety of fruits and vegetables.’
People should also limit salt, sugar, animal fat, processed foods and alcohol, she said.
WHAT SHOULD A BALANCED DIET LOOK LIKE?
Meals should be based on potatoes, bread, rice, pasta or other starchy carbohydrates, ideally wholegrain, according to the NHS
• Eat at least 5 portions of a variety of fruit and vegetables every day. All fresh, frozen, dried and canned fruit and vegetables count
• Base meals on potatoes, bread, rice, pasta or other starchy carbohydrates, ideally wholegrain
• 30 grams of fibre a day: This is the same as eating all of the following: 5 portions of fruit and vegetables, 2 whole-wheat cereal biscuits, 2 thick slices of wholemeal bread and large baked potato with the skin on
• Have some dairy or dairy alternatives (such as soya drinks) choosing lower fat and lower sugar options
• Eat some beans, pulses, fish, eggs, meat and other proteins (including 2 portions of fish every week, one of which should be oily)
• Choose unsaturated oils and spreads and consuming in small amounts
• Drink 6-8 cups/glasses of water a day
• Adults should have less than 6g of salt and 20g of saturated fat for women or 30g for men a day
Source: NHS Eatwell Guide