Simple Guidelines on "Good" vs. "Bad" Fats

Research into how diet can affect health and prevent disease has expanded almost as fast as the obesity rate in the United States.

"Sometimes it's a struggle for patients and their physicians to keep up with constantly changing dietary guidelines," says Joan M. Neuner, MD, MPH, Medical College of Wisconsin Assistant Professor of Medicine. "Patients are understandably confused. But I try to tell them that nothing dramatic has really changed. In general, science keeps returning to the overall principle - that Americans are eating too many calories and not getting enough exercise."

Dr. Neuner noted that when she graduated from medical school, US researchers were just beginning to observe the rise in obesity and related conditions like diabetes and heart disease. At the same time, the lives of American adults and children were becoming increasingly sedentary. Men and women were working longer hours and families were spending more time commuting. Meanwhile, food manufacturers were rapidly churning out more convenience foods to meet the rising demand. Suddenly, the obesity rates began to soar.

"It's amazing," Dr. Neuner says. "We knew obesity was on the rise, but no one expected it to skyrocket so quickly." That's one reason so much nutrition research is being published - including a great deal of interest in the various types of fats.

Fats Are Essential to Health
Fat is a major source of energy for the body and aids in the absorption of vitamins A, D, E, and K and carotenoids. Both animal- and plant-derived food products contain fat, and when eaten in moderation, fat is important for proper growth, development, and maintenance of good health.

As a food ingredient, fat provides taste, consistency, and stability and helps you feel full. Fats are an especially important source of calories and nutrients for infants and toddlers (up to 2 years of age), who have the highest energy needs per unit of body weight of any age group.

But fats are increasingly being put into "good" and "bad" categories - a simplistic but effective way to help people remember which types to stay away from. "Good" fats include those found in foods such as lean fish and poultry, nuts, and olive, peanut and canola oils. "Bad" fats include saturated fats from certain meats, butter, cream and certain oils that can raise cholesterol levels and increase the risk of heart disease. One type of fat has shot to the top of the bad foods list - trans fatty acids, also called trans fat.

While unsaturated fats (monounsaturated and polyunsaturated) are beneficial when consumed in moderation, saturated and trans fats are not. Scientific evidence shows that consumption of saturated fat, trans fat, and dietary cholesterol raises low-density lipoprotein (LDL), or "bad cholesterol," levels, which increases the risk of coronary heart disease (CHD). According to the National Heart, Lung, and Blood Institute (NHLBI), more than 12.5 million Americans have CHD, and more than 500,000 die each year, making CHD one of the leading causes of death in the United States.

What Are Trans Fats?
Trans fats are man-made fats that occur in foods when manufacturers use hydrogenation, a process in which hydrogen is added to vegetable oil to turn it into a more solid fat.

Trans fats are found in vegetable shortening, some margarines (especially stick margarines), crackers, candies, cookies, snack foods, fried foods, baked goods, salad dressings, and other processed foods that busy Americans buy for their convenience and easy availability.

Like saturated fats from animal products, trans fats can raise cholesterol levels and increase the risk of heart disease. Even worse, trans fats can also raise triglycerides and lower the level of the so-called good cholesterol, or the high-density lipoproteins (HDLs), while increasing the levels of the bad cholesterol, or LDLs, the low-density lipoproteins.

Consumers can find trans fats listed on food labels directly under the line for saturated fat. Many foods contain several different kinds of fat - including saturated, polyunsaturated, monounsaturated and trans fat. What do they all mean?

• Saturated fat: Found in eggs, butter, meat, poultry, chocolate, coconut, palm oil and lard.
• Polyunsaturated fat: Found in some vegetable oils such as safflower, corn, sunflower, soy and cottonseed oils.
• Monounsaturated fat: The "good" fat, found in fish and lean poultry, avocados, nuts, and olive, peanut and canola oils.
• Trans fat: Found in many margarines and shortenings, and in commercial baked goods and fried foods.

The US Food and Drug Administration (FDA) notes that you can make a few simple choices every day to help you to keep your consumption of saturated fat, trans fat, and cholesterol low while consuming a nutritionally adequate diet, for instance:

• Replace saturated and trans fats in your diet with monounsaturated and polyunsaturated fats. These fats do not raise LDL cholesterol levels and have health benefits when eaten in moderation. Sources of monounsaturated fats include olive and canola oils. Sources of polyunsaturated fats include soybean oil, corn oil, sunflower oil and foods like nuts.
• Choose vegetable oils (except coconut and palm kernel oils) and soft margarines (liquid, tub, or spray) more often because the combined amount of saturated fat and trans fat is lower than the amount in solid shortenings, hard margarines, and animal fats, including butter.

Read Labels Carefully
Manufacturers of foods that are low in saturated fat and trans fat have begun marketing around their products' health benefits. Consumers should be cautious, however, Dr. Neuner says. "Many foods contain several kinds of fats," she notes. "Read the labels carefully and make sure you get all the information."

Now that Americans are told to add healthy fats to their diets but avoid or sharply limit the saturated and trans fats found in so many favorite foods, what's next?

Stick with the basics, Dr. Neuner recommends. Remember that saturated fat and trans fat raise LDL cholesterol levels in the blood and dietary cholesterol also contributes to heart disease. Whenever possible, choose foods low in saturated fat, trans fat, and cholesterol as part of a healthful diet.

"This really isn't such a sea change from what we already know," she says. "We'll continue to refine the details, but the main message is the same: Eat fewer calories and get more exercise. Be cautious with processed foods, and choose more fruits and vegetables as snacks as often as possible."

Barbara Abel
HealthLink Contributing Writer

Eileen Early, BA, BSN, RN
HealthLink Editor

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.