Polyunsaturated fat equals good, saturated fat equals bad. That’s the old adage you’ve been fed for years about why you should reach for vegetable oils instead of whole milk, cream, butter, cheese and other animal fats.
For decades, you swapped these villainized fats for vegetable, soybean and sunflower oil thinking you were making a healthy choice for your heart and your waistline. But new controversial research is turning that notion on its head.
This week, new research garnered international headlines: “Butter no worse for you than vegetable oil,” “Experts say vegetable oil may not be as healthful as we thought,” and “Butter is no more deadly than vegetable oil” were some of the prime examples.
The U.S. researchers may be sounding the alarm about vegetable oil, but critics of the study say consumers shouldn’t put down polyunsaturated fats just yet.
Global News looked at the study’s findings, the counter-arguments and the bottom line from Canadian experts.
The study’s findings: American scientists out of the National Institutes of Health and the University of North Carolina wanted to see if trading saturated fat for vegetable oils could help lower heart disease risk and blood cholesterol levels.
The swap is a “diet-heart hypothesis” – what they say is a widely held theory that’s “never been causally demonstrated” in randomized, controlled studies, the gold standard in medical research. They say it’s left them with a 50-year-old question mark.
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The researchers dug up data from a large randomized controlled trial that’s 45 years old. It was called the Minnesota Coronary Experiment (MCE) and it followed the health of more than 9,400 participants from state mental hospitals and nursing homes for about 4.5 years. Their ages ranged from 20 to 91, but the average age was 52.
Some of the study participants had their saturated fats swapped with vegetable oil rich in linoleic acid, while a control group ate a diet high in saturated fat, such as margarine, shortening and animal fat sources.
Turns out, the vegetable oil diet helped with lowering cholesterol levels, but it didn’t necessarily translate into improved survival rates. The group that saw the greatest reduction in blood cholesterol ended up with the highest risk of death.
Soundbite:: “The benefits of choosing polyunsaturated fat over saturated fat seem a little less certain than we thought,” University of Queensland doctor, Lennert Veerman, wrote in a linked editorial.
The counter-arguments: Critics weren’t impressed with the study’s brazen comments. Instead, they told consumers to stick to current recommendations to watch their intake of saturated fats.
For starters, they note that people in the study were eating twice the amount of linoleic acid that’s in a normal diet.
Corn oil was added to their salad dressings, lean ground beef, milk and cheese. They were on the diet for about 41 to 56 months. One critic suggested the study is flawed because the trial was too small and the participants weren’t on the diet long enough for effects to truly take hold.
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Keep in mind, the participants were older in age at 52 and were in mental hospitals and nursing homes. Their health may have been affected in other aspects, too.
For their part, the study authors concede that their findings may not apply to the general public because of this.)
The study is also 45 years old. People weren’t eating and living the same way as we do now. Food quality has also changed over the past four decades.
Soundbite: “This research cannot be used to draw any conclusions about a healthy diet. From the large amount of information from other studies, we know that risk of heart disease will be lower if saturated fats – mainly from red meat and dairy fat – are replaced by unsaturated fats from liquid vegetable oils such as soybean, corn, olive, and canola oils for cooking, on salads, and at the table,” Dr. Maryam Farvid, a Harvard School of Public Health professor, told Health Day.
The bottom line: Dr. Martha Belury, a nutrition professor at Ohio State University, specifically studies cooking oil in our diets and its effect on body composition.
Her latest findings pointed to a link between linoleic acid helping to lower diabetes and heart disease risk, but it isn’t a cause and effect, necessarily.
She had similar concerns as other critics of the study.
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“It’s an attempt to bring back to life some data from the 1960s. My concerns are that the food we ate then, and the things we were doing are so different from what we’re doing 50 to 60 years later,” she told Global News.
Christy Brissette, a Toronto-based registered dietitian and president of 80 Twenty Nutrition, said that if you’re concerned, try to control where the oil in your diet is coming from. The fat you should be worried about is typically in the prepacked food you eat, like trans fat, as a key example.
“These oils are often used in processed foods, so cutting down on packaged food and cooking at home more often can help you control the types of fats you’re getting,” Brissette said.
Belury said Canadians can keep cooking with vegetable oil and can even mix it with other fats, such as olive oil.
Read the full study in the BMJ.
carmen.chai@globalnews.ca
Follow @Carmen_Chai
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