It’s Pretty Basic: Lower Your Saturated Fat Intake

The story of dietary fats is a slippery one that gets more complicated the more research is published. But despite the tangle of information, some rules remain clear.

A decade or so ago things seemed pretty simple: Saturated fats were bad because they raised levels of cholesterol, a primary risk factor for heart disease and stroke. Polyunsaturated fats were good because they didn’t.

Then we started learning about low-density lipoprotein (or LDL), the bad cholesterol, and high-density lipoprotein (or HDL), the good cholesterol. And researchers started talking about monounsaturated fatty acids, such as those in olive oil.

Saturated fatty acids, we learned, would raise LDL and HDL. If you substituted polyunsaturated fatty acids the LDLs went down, but so did the HDLs, though not as much. Monounsaturates, on the other hand, lowered LDLs but slightly boosted HDLs when substituted for saturates.

Then up popped another risk factor: triglycerides, the molecules that transport the fatty acids and vitamins through the blood. High triglyceride levels also increase risk of heart disease and other disorders. Saturated fats elevate triglycerides, as do polyunsaturates, though not as much. Monounsaturates may lower triglycerides slightly.

As intricate as this fat story already was, the plot thickened even more.

Food manufacturers began eliminating saturated fats like butter, lard and tropical oils, replacing them with polyunsaturated vegetable oils that had been chemically stiffened and stabilized. But these “hydrogenated oils” created new troublesome substances called trans fatty acids.

Research showed that trans fatty acids can raise LDLs and may lower HDLs. Some scientists have asked the government to require them to be labeled as saturated fats.

The truth is that although the terms saturated, polyunsaturated and monounsaturated are convenient, there are dozens of kinds of fats in the diet, each with its own profile.

“Fats do have some beneficial effects, but how much and in what proportion is still a big hole in our knowledge,” says Penny Kris-Etherton, professor of nutrition at Pennsylvania State University.

“It’s complex, but there are some basics. Universally, scientists agree on the need to lower saturated fat, to less than 10 percent of calories. If you do that, you also reduce your total fat and calories. For some people that diet is perfectly appropriate, especially for those who are overweight.”

But some people don’t need to lose weight, or don’t want to. If you reduce saturated fat, with what will you replace those calories - carbohydrates, or another fat?

Monounsaturates, which are pretty neutral, probably won’t decrease your HDL or increase triglycerides.

But omega 3s - the so-called “fish oils,” which are polyunsaturated fats - also may have some benefits. They may counteract the inflammation of rheumatoid arthritis and lower cholesterol. And they help keep blood platelets from sticking and clots from forming, which protects against heart disease.

Omega 3s must come from eating fish; they aren’t readily available in vegetable oils. You can take fish oil supplements, but only under medical supervision, Kris-Etherton says.

One solution is to eat two fish meals a week in place of meat. That supplies a good measure of omega 3 fatty acids while decreasing saturated fat intake, she says.

If you replace the saturated fat with monounsaturates from olive oil, canola and nuts, be especially cautious of the amount, Kris-Etherton says: “Just because you change from high-fat whole milk to skim doesn’t mean you can start sopping up a saucer of olive oil with your bread.”

Replacing fat calories with carbohydrates has many advantages. Population studies worldwide show that the more fat that people consume, the more overweight they are, she says. Skinnier people consume fewer fat calories.

But there doesn’t have to be one diet that fits everyone. In the future, Kris-Etherton says, we could be looking at combinations of oils, even genetically engineered fats, to get the best fatty acid profile.

“That’s probably far away,” she says.