For more than a few decades the medical community told us that fat was bad. Much maligned, fat was deemed enemy number one of hearts and minds (clogged arteries, heart attacks and strokes, oh my!) as well as waistlines. However, as new research shows, the tide against some fats is indeed turning.
Thinking saturated fat – animal-based fats such as those found in dairy products and red meat – was the enemy of all circulatory systems, the medical community recommended a low-fat diet to prevent cardiovascular disease for decades.
Now? Not so much.
In 2005, a huge Harvard study – nearly 80,000 U.S. women over 20 years (1980 to 2000) – was published in The American Journal of Epidemiology in which specific types of dietary fat were examined for their association with coronary heart disease. Results showed a benefit of polyunsaturated fats (olive, soybean, corn and sunflower oil and fatty fish like salmon and mackerel) in preventing coronary disease.
At the opposite end, the study showed the intake of trans-fat, man-made trans fatty acids created by adding hydrogen to liquid vegetable oils to solidify them (think margarine sticks, coffee creamers, cookies, cakes, pie crusts, ready-made frosting, and other junk foods), were found to increase the risk coronary heart disease in women. While the Harvard study didn’t venture into the arena of “saturated fats,” it certainly reflected a trend recognizing the rise of the “good fats.”
As for those naughty fats, in 2013, the FDA took steps to reduce trans fats in processed foods and declared that they were no longer "generally recognized as safe." While food manufacturers curbed their use of trans fat, the FDA took more definitive action last June, ordering food companies to eliminate trans fats from their products within the next three years.
Today, more studies are taking on saturated fats and yielding interesting, perhaps even surprising results. This year, The Journal of Nutrition published one study concluding there was no association between the dietary intake of saturated fats and the incident of major coronary events (heart attack, sudden death) or mortality in patients who already had established cardiovascular disease.
Then, this summer, a Canadian systematic review and meta-analysis of observational studies appeared in the British Medical Journal. As with the Harvard study, the McMaster University researchers didn’t have much good to say about trans fats either as they were associated with an increased risk of all cause death and cardiovascular deaths. However, the study found no association between the consumption of saturated fats and cardiovascular disease, coronary heart disease, stroke, diabetes or mortality.
“These studies, and this one in particular, are important because they tell us we may be giving our patients the wrong advice that ‘all fat is bad,’” said Dean G. Karalis, MD, FACC, FNLA, director of Preventive Cardiology, at Pennsylvania Hospital, a clinical professor of Medicine at Penn’s Perelman School of Medicine and president elect of the Northeast Lipid Association. “We are now finding out that a low fat diet may have unintended bad consequences. Not all fat is bad and having people avoid healthy high fat foods and turn to foods rich in sugar and refined carbohydrates is fueling the epidemic of obesity and diabetes in our country,”
According to Karalis, some fat – saturated fat from plant sources such as nuts or avocados – is definitely good. Fat from oily fish is also healthy and reduces one's risk of heart disease. “These latest studies support that allowing our patients to increase the fat in their diet, as long as it’s the right type of fat, may be the best way to reduce an individual's risk of heart disease and diabetes,” Karalis said.
Even the new U.S. dietary guidelines no longer limit total fat intake.
However, Karalis cautions that these current studies are only the beginning.
“The British Medical Journal study was a well done systematic review, but has limitations inherent to any such retrospective study,” Karalis said. “One needs to be cautious about rigidly interpreting the results.“
For example, the researchers could not control for what foods were eliminated or reduced in quantity when individuals increased the fat intake in their diets. Any adverse effects of a diet high in saturated fat may have been offset by the benefit of a diet limiting sugar and refined carbohydrates, he said.
“We also need more research in what type of fat is best when we recommend an individual increase the fat in his or her diet,” he added.
While the researchers continue to fight the good fat fight, what’s the bottom line for regular folks just trying to do the right dietary thing for their health?
“Based on this and other studies, here is what we know so far: trans fats are bad and should be avoided. Saturated fats from animal sources such as red meat should be minimized and good fats from plants and fish should be encouraged,” Karalis said. “I will gladly recommend that patients increase their total fat intake with these good fats at the expense of sugar and refined carbohydrates.”