When it comes to reducing risk for heart disease, what should people pay more attention to: total fats, saturated fats or trans fats? What does that mean when it comes to choosing among the many different types of foods available today?
The following are answers to commonly asked questions about trans fat—what they are, why they are found in foods, and their impact on health. These answers can help you understand the role trans fats play in foods.
What is dietary fat?
Dietary fats are the fats found in foods. They are an essential part of a healthful diet.
Fatty acids are the building blocks of dietary fats. All dietary fats contain a mixture of saturated and unsaturated fatty acids. The type of fatty acid that predominates determines whether a fat is solid or liquid, and whether it is characterized as saturated or unsaturated. Fats such as tallow, lard and butter, and vegetable oils such as palm, palm kernel and coconut oils, which are harder at room temperature, contain higher levels of saturated fatty acids. They are considered saturated fats. Oils such as soybean, canola, cottonseed, corn and other vegetable oils, which are liquid at room temperature, contain higher levels of unsaturated fatty acids. They are considered unsaturated fats.
What are the different types of fatty acids?
Fatty acids are classified as saturated or unsaturated depending on their structure. Unsaturated fats are further subdivided into monounsaturated and polyunsaturated fats.
What are trans fats?
Trans fats are unsaturated fatty acids formed when vegetable oils are processed and made more solid or into a more stable liquid. This processing is called hydrogenation. Trans fats also occur naturally in low amounts in some foods.
Trans fats from all sources provide two to four percent of total calories compared with 12 percent from saturated fat and 34 percent from total fat in the American diet. The majority of trans fats come from processed foods. About one-fifth of trans fats in the diet come from animal sources such as certain meats and dairy products.
What foods contain trans fats?
Trans fats are present in variable amounts in a wide range of foods, including most foods made with partially hydrogenated oils, such as baked goods and fried foods, and some margarine products. Trans fats also occur naturally in low amounts in certain meats and dairy products.
Why are trans fats in foods?
Trans fats form when an oil is partially hydrogenated. The process converts oils into a more stable liquid or semi-solid form.
Partially hydrogenated oils are used in processed foods because they help produce high quality food products that stay fresh longer and have a more desirable texture. It is not always possible to substitute unhydrogenated oils because of differences in the way the oils work to produce acceptable food products.
For example, by using partially hydrogenated vegetable oil to make some margarine products, manufacturers can produce a spreadable topping that is lower in saturated fat than butter and can be used immediately upon removal from the refrigerator. Likewise, manufacturers can produce shortenings to make French fries, flaky piecrusts and crispy crackers. Products made with partially hydrogenated oils also resist rancidity (when fats develop an off-flavor) longer than those using unhydrogenated oils. Foods that contain these oils must list "partially hydrogenated vegetable oil" in the ingredient statement of the food label.
Are partially hydrogenated oils used for any other reasons?
Fats and oils containing trans fats are used in place of baking and frying fats that have higher levels of saturated fats. Examples of fats with higher levels of saturated fats include lard, butter and highly saturated vegetable oils like palm, palm kernel and coconut oils. In the mid-1980s, the food industry responded to recommendations from health authorities and interest from consumers to reduce the amount of highly saturated vegetable oils along with animal fats in the food supply. The best, and in many cases the only, available alternative was to reformulate products by substituting partially hydrogenated vegetable oils for the highly saturated fats.
How do trans fats, saturated fats and dietary cholesterol impact blood cholesterol?
The National Academy of Sciences’ Institute of Medicine recently concluded that saturated fat, trans fat and dietary cholesterol all raise blood LDL cholesterol (the “bad” cholesterol). In addition, some evidence suggests that intake of trans fats lowers HDL cholesterol (the “good” cholesterol).
How does blood cholesterol relate to heart disease?
High blood cholesterol is one risk factor for cardiovascular heart disease. People with high blood cholesterol levels are more likely to develop the disease.
What other factors play a role in heart disease?
Cardiovascular disease is very complex. While blood fats such as cholesterol play a part in the development of the disease, there are a number of other factors involved such as diabetes, hypertension, blood clotting, gender, age and heredity.
In addition, lifestyle factors other than diet play key roles in the development of heart disease. Research clearly shows that increased physical activity and maintaining a healthy weight are critical factors in reducing risk for cardiovascular disease.
Should I reduce my intake of trans fat?
The Institute of Medicine (IOM) recently recommended that the intake of trans fat as well as saturated fat and cholesterol should be as low as possible while consuming a nutritionally adequate diet. Because trans fat, saturated fat, and cholesterol are difficult to avoid in ordinary, non-vegan diets, consuming none would require significant changes to the total diet. According to the IOM, such changes may have undesirable effects, which may result in inadequate intakes of protein and certain micronutrients. More research is needed to determine realistic levels of trans and saturated fat and cholesterol intakes that are consistent with a nutritionally adequate diet for different population groups.
The contribution of saturated fat to American diets is much greater than that of trans fats. Individuals in the United States consume 5 to 6 times the level of saturated fats than trans fats.
How can I reduce the amount of trans fats in my diet?
You can lower the amount of trans fats in your diet by following the advice of health professionals:
- Reducing total fat intake generally will help lower your intake of saturated fat, trans fats and cholesterol.
- Reducing trans fat intake should not be accomplished by substituting food higher in saturated fats in the diet.
- Monounsaturated and polyunsaturated fats may be substituted while keeping total fat intake moderate.
What food choices can I make to help lower intake of saturated fats and trans fats in my diet?
- Most liquid vegetable oils are naturally lower in saturated fats and are trans fat-free. These include soybean, canola, corn, olive, safflower and sunflower oils.
- Margarine products contain significantly lower amounts of saturated fats than animal fats such as butter, tallow, and lard, or solid shortenings. And, many margarine products are low in trans fats or are trans fat-free. (Remember that liquid and lower fat versions of margarines do not substitute well in recipes where shortening, stick margarine or butter is required.)
- New fat processing technologies have produced some trans fat-free products. Additional products will likely become available in the near future.
- To lower intake of saturated fats and trans fats, try reduced-fat, low-fat, fat-free and trans fat-free versions of frequently consumed foods.
Are trans fats included on the Nutrition Facts panel?
The Food and Drug Administration (FDA) regulates what is put on the Nutrition Facts panel of most processed foods. (The USDA regulates labeling for meats, fish and poultry products.)
The FDA published the final rule for trans fat labeling on July 9, 2003. The new label will require a trans fat line to be declared directly under the saturated fat line of the Nutrition Facts panel on all products with a measurable level of trans fat (at least 0.5 grams per serving). This rule will be effective January 1, 2006; however, food and beverage companies are allowed to add the trans fat line before the deadline.
FDA currently requires that total fat, saturated fat and cholesterol be listed on the Nutrition Facts panel. This requirement grew out of years of scientific research and dietary recommendations by major health and nutrition organizations. Currently, the Daily Values for total fat, saturated fat and cholesterol are based on the science available at the time of the implementation of the Nutrition Labeling and Education Act (NLEA) of 1990. The NLEA requires that nutrients listed in the Nutrition Facts panel be declared in a manner that helps consumers understand the contribution of a food to the total daily intake of that nutrient. The % Daily Value has been added to food labels for this purpose.
The recent recommendations of the Institute of Medicine suggest that intakes of saturated fat and cholesterol, as well as trans fat, be as low as possible while consuming a nutritionally adequate diet.
However, the IOM did not provide sufficient information for FDA to set a Daily Value for trans fat. The IOM has convened an expert committee to identify general guiding principles for using the Dietary Reference Intakes in food labeling and will examine the best way to communicate the Institute of Medicine’s dietary guidance for trans fat, saturated fat, and cholesterol on food labels.
