Fat and Cholesterol: Are They as Bad as We Once Thought?

Health Professional, Medical Reviewer

We all need some fat in our diet, since dietary fat is an essential nutrient.  Fat helps you to absorb certain vitamins, and it gives you energy.  We used to believe that all fat was bad for you, and the general recommendation was to avoid dietary fat as much as possible. What we now know is that it’s not the fat we eat, but the type of fat we choose to eat that affects heart health.  And some of it isn’t as bad as we once thought.

Decades of research has shown that saturated fat (which comes primarily from animal sources) and trans-fat (which is found in many packaged products and baked goods) has been shown to increase both your total serum cholesterol and your LDL (or “bad”) cholesterol, which can increase your risk of cardiovascular disease.  The American Heart Association (AHA) and the American College of Cardiology (ACC) both recommend that no more than 5-6 percent of our daily calories should come from saturated fat. They also recommend that trans-fat (which has also been shown to harm your HDL or “good” cholesterol) should be limited as much as possible.

Dietary fat: good or bad?

We were once told that all dietary fat was bad for us.  In the 1990s and the early 2000s there was a huge surge in products on the market that were both “low-fat” and “fat-free.” This led to an overconsumption of carbohydrate intake resulting in weight gain for many Americans. More current research suggests not only that all fats aren’t bad for us, but that replacing most of the unhealthy dietary fats in our diets with both monounsaturated and polyunsaturated fats can help to decrease the risk of heart disease. The AHA suggests that 25-35 percent of our total daily calories should come from these healthier fats. Good sources include avocadoes, olives, non-tropical vegetable oils, nuts, seeds, and fish. Research shows that people who consume a diet high in these unsaturated fats have a low risk of heart disease. So it’s not the fat—but the type of fat—that’s important.

What about dietary cholesterol?

Cholesterol is essential to the human body, but since the body can manufacture all of the cholesterol it needs, getting cholesterol from your diet isn’t necessary. The previous Dietary Guidelines for Americans published in 2010 recommended that we limit dietary cholesterol to no more than 300 mg per day. But the new 2015 Dietary Guidelines for Americans have removed this restriction, basing this on a report by the AHA and ACC that there is insufficient evidence to support that restricting dietary cholesterol has an effect on lowering LDL cholesterol.  The new Dietary Guidelines also recommend a slightly higher limit of saturated fat intake, which is no more than 10 percent of our total caloric intake. Additional recommendations include replacing solid fats with liquid fats whenever possible.

The Bottom Line

This new approach, which for many people is changing from “low-fat” to “pro-fat,” must be individualized for each person based on their own unique risk factors for cardiovascular disease. Concentrating on the composition of our entire diet with a focus on nutritional quality is a more effective approach to nutrition and health that focusing on total fat intake alone.  Your physician and/or registered dietitian is the best person to help you individualize your diet based on your unique nutritional needs and cardiovascular risk factors.

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