For decades, we’ve been told that fats in food are unhealthy. New research is now prompting medical experts to re-evaluate fat — and it’s not totally taboo.

“A lot of what we believed about fats has turned out not to hold up to scientific scrutiny,” says Steven Nissen, MD, Chairman of the Department of Cardiovascular Medicine at Cleveland Clinic.

A recent study analyzed earlier research that looked at fat and heart disease. The outcomes surprised many people — including doctors.

Saturated fat: OK in moderation

Doctors have historically urged people to severely limit saturated fat — the type of fat found in animal products such as meat, whole milk, ice cream and butter. But the newer research shows saturated fat may unfairly have been given a bad rap.

More studies are needed on saturated fat, Dr. Nissen says. But in the meantime, it’s all right to consume it in moderation.

“If you want to use a little bit of butter to flavor what you’re cooking, it’s not a sin,” Dr. Nissen says.

Moderation is the key to consuming fat, he says.

“There are a lot of reasons why you want to hedge your bets, but you don’t have to absolutely avoid the saturated fats,” Dr. Nissen says.  “You want to keep them under some control.”

Unsaturated fat: May benefit your heart

Then there is unsaturated fat, which can have a beneficial effect on your heart when eaten in moderation and when used to replace saturated fat and trans fat in your diet.

Unsaturated fats provide nutrients to help develop and maintain your body’s cells. They also can help reduce bad cholesterol levels in your blood, which can lower your risk of heart disease and stroke. Oils that contain unsaturated fats are typically liquid at room temperature but start to turn solid when chilled.

Unsaturated fat falls into two types — polyunsaturated and monounsaturated:

• Polyunsaturated fats were shown to be fairly neutral in terms of heart health in recent research. These fats, which are in foods such as salmon and canola oil, were neither good nor bad, but “trending toward favorable,” Dr. Nissen says. Oils rich in polyunsaturated fats also provide essential fats that your body needs but can’t produce itself — such as omega-6 and omega-3 fatty acids. These nutrients are important for many functions in the body.
• Monounsaturated fats provide the most health benefit, according to research, and are an important component of the heart-healthy Mediterranean diet, Dr. Nissen says. They are found in foods such as olive oil and sesame oil and in nuts such as almonds or walnuts. “There’s every reason to believe that the nuts that contain unsaturated fats like almonds and walnuts are a very healthy choice,” he says. But make sure they’re in their raw form. “Chocolate candy-coated nuts are not the way to go,” Dr. Nissen says.

Trans fat: Still dangerous

The one type of fat that is hands-down unhealthy? Trans fat. Trans fats are artificial, man-made substances created by bubbling hydrogen gas through healthy oils.  They’re primarily found in processed foods and typically are listed on food packages as “trans fat” or “partially hydrogenated oil.”

In November 2013, the U.S. Food and Drug Administration (FDA) made a preliminary determination that partially hydrogenated oils are no longer Generally Recognized as Safe (GRAS) in human food.

“Everybody agrees trans fats are unhealthy,” Dr. Nissen says. “They’re strongly associated with developing coronary artery disease.”

In food processing, trans fats are easy to use, inexpensive to produce and last a long time. They give foods a desirable taste and texture. Many restaurants and fast-food outlets use trans fats to deep-fry foods because they can be used repeatedly in commercial fryers.

Trans fats raise your bad (LDL) cholesterol levels and lower your good (HDL) cholesterol levels. Eating trans fats increases your risk of developing heart disease and stroke. It’s also associated with a higher risk of developing type 2 diabetes.

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