A large new review of existing research suggests that for healthy people, a reasonable amount of saturated fat in the diet poses no health risk.
Trans fats, on the other hand, were associated with an increased risk of death from any cause, death from cardiovascular disease and a diagnosis of coronary heart disease.
Dietary guidelines recommend that saturated fats, found in animal products like meat, butter and egg yolks make up no more than 10 percent of daily calories. Trans fats, like the partially hydrogenated oils that keep processed foods and hard margarines shelf-stable, are primarily industrially produced and should provide no more than one percent of daily calories.
For the new review, researchers at several Canadian institutions including McMaster University in Hamilton, Ontario, included data from 41 studies of the association between saturated fat intake and health outcomes, covering more than 300,000 people, and 20 studies of trans fat intake and health outcomes that covered more than 200,000.
Saturated fat intake was not tied to coronary heart disease, cardiovascular disease, stroke or type 2 diabetes, but its link to risk of death from coronary heart disease was unclear.
Consuming industrial trans fats was associated with a 34 percent increase in all-cause mortality, a 28 percent increased risk of heart disease mortality and a 21 percent increase in the risk of heart disease.
None of the studies they included were randomized controlled trials, the most rigorous type of study; all were based on observation over time, so other factors in participants’ lives could have played a role in their health outcomes.
Several reports since 2010 have confirmed that saturated fats are not associated with heart attack or stroke.
Unlike saturated fats, trans fats lower "good “ HDL cholesterol.
The U.S. Food and Drug Administration has given food manufacturers until 2018 to remove trans fats from the food supply.
Individual saturated fats vary widely in their food sources as well as their potential health effect. Some are harmful while others may actually be beneficial, so their total amount in the diet seems to have no association with health outcomes like death.
More research on saturated fats is needed, and trans fats should be totally avoided in the diet, experts say.
Eating well means replacing saturated fats with polyunsaturated fats rather than carbohydrates, particularly refined and processed carbohydrates.
“There are still people who will benefit from controlling the amount of saturated fat they consume, but it's not the most important part of the diet to be concerned about,” the researchers said.
Source: The BMJ, online August 11, 2015.
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