A huge new Canadian study is challenging what we thought we knew about low-fat diets and cardiovascular health.
The PURE study from McMaster University, which involved more than 135,000 people from 18 countries, found that a high-carb diet (in which more than 60% of one’s calories come from carbs) was associated with a higher risk of premature death. On the other hand, diets that contained a moderate amount of all types of fat — including supposedly “unhealthier” unsaturated fats — were linked to a reduced risk.
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“Contrary to popular belief, increased consumption of dietary fats is associated with a lower risk of death,” said lead author Mahshid Dehghan, a nutrition epidemiologist at McMaster’s Population Health and Research Institute.
“Those with a high-fat intake, about 30% of energy intake, had a 23% lower risk of mortality and an 18% lower risk of stroke, compared to the low-intake group, which had 11% energy from fat,” Dehghan said, as he presented his findings this week in Barcelona to the European Society of Cardiology Congress.
“The association with lower mortality was also seen with all major types of fat, by which I mean saturated, monounsaturated and polyunsaturated fatty acids,” he added.
The news comes as a surprise to those following the conventional wisdom about nutrition, which has long suggested that fats — and in particular saturated fats found in meat and dairy products — should be eaten in moderation. Also good for you are saturated fat from nuts, avocados, vegetable and olive oils and polyunsaturated fat found in walnuts, sunflower, fish and soybean oils.
“Contrary to popular belief, increased consumption of dietary fats is associated with a lower risk of death.”
Compared to many existing global guidelines, the study suggests that most people eat way too many carbs and not nearly enough fat. The study’s authors speculate this may be because most studies linking fat to heart disease have come from North America and Europe, which have the highest consumption of fat worldwide.
In western cultures, where there is an excess of fat, reducing fat may be helpful for lowering heart disease rates — that is, if people aren’t replacing fat with carbohydrates. This may not necessarily ring true for other parts of the world, where carbohydrates make up a large part of the diet. For those countries, cutting back on carbs and increasing consumption of fat may be more helpful.
Overall, a diet that provides more than 60% of energy from carbohydrates was associated with a 28% higher risk of premature death. In some countries, like China, south Asia and Africa, the amount of carbohydrates in the diet was even higher, at 63% to 67%.
For optimal cardiovascular health, Dehghan instead recommends 50 to 55% carbohydrates and 35% total fat of all types.
“There’s a sweet spot for carbohydrates, which is about 55% of energy intake,” he said, adding that when it comes to fats, saturated fat is far better for you than was once believed — and that a diet containing 10 to 13% of calories from saturated fat was ideal, and that going below 7 per cent could be harmful.
“The message of our study is moderation, as opposed to very low or very high intake in consumption of both fats and carbohydrates,” said Deghan.
“We’re not advocating an extreme diet,” agreed co-author Andrew Mente. “We’re not saying that people should go on a low-carb, very high-fat diet because we didn’t find any benefit with a very low-carb diet either.”
While “moderation” is always an easy takeaway for any study like this one, there are some more practical applications here, too. The federal government is currently in the process of revamping Canada’s Food Guide, and Mente’s research may help with creating more healthful guidelines.
“[Rather] than putting limits on total fat and saturated fat, perhaps we should be putting limits on the amount of carbohydrates they consume,” suggested Mente.