Fats have a place at the table, as long as they’re the right kind
Until recently, fat was persona non grata in the dietary world. Studies over the years linking saturated fat to heart disease and other conditions led to the vilification of all fats—as well as advice from the experts to replace fats with carbohydrates. But this simplistic view has resulted in record levels of obesity and diabetes. What went wrong? For one thing, not all fats are the same. Some—like those from plants and fish—are downright good for you, helping to reduce your risk of heart disease, stroke, and other chronic conditions. Also, fat can help satisfy hunger so you’re not tempted to eat greater quantities of other foods. The trick is knowing which fats to include in an overall healthy eating plan and which to avoid. On this page, you’ll find charts, tables, and links to information that can help you choose what’s right for you. To your health!
Types Of Fat
The fat family is an extended clan. What all fats have in common is a chain of carbon atoms bonded to hydrogen atoms. They differ in the length and geometry of their carbon backbones, how the carbon atoms are connected to each other, and the total number of hydrogen atoms attached. Some are good for the heart, circulatory system, and general health (the unsaturated fats), while others aren't so good (saturated fats), and others are downright harmful (trans fats).
Almost all of the fats in our diet are triglycerides—three fatty acids bound together by a "glue" known as glycerol. There are four main categories of fatty acids—monounsaturated, polyunsaturated, saturated, and trans fatty acids. To keep things simple, we'll usually refer to fatty acids as fats.
Monounsaturated fat. The Greek prefix mono, meaning one, refers to the single instance along the carbon backbone where two carbon atoms are connected by a double bond. This reduces the number of hydrogen atoms the carbon chain can hold by two and gives the molecule the shape of a bent stick. This shape keeps adjacent molecules separated, making monounsaturated fats liquid at room temperature. Foods rich in monounsaturated fats include canola, peanut, and olive oils; avocados; nuts such as almonds, hazelnuts, and pecans; and seeds such as pumpkin and sesame seeds.
Polyunsaturated fat. These fats have two or more double bonds. This makes them even more bent than monounsaturated fats. They, too, are liquids at room temperature. Our bodies don't make polyunsaturated fats, so we need to get these essential fats from a variety of sources. Polyunsaturated fats can be subdivided into the omega-6 or omega-3 groups. The number refers to how far the first double bond is from the end (omega) of the carbon chain:
- Omega-3 fats help protect the heart from lapsing into potentially deadly erratic rhythms, ease inflammation, inhibit the formation of dangerous clots in the bloodstream, and lower levels of triglycerides, the most common type of fat-carrying particle in the blood. An excellent way to get omega-3 fats is by eating fish two or three times a week. Good plant sources of omega-3 fats include chia seeds (sold as Salvia), flaxseeds, walnuts, and oils such as flaxseed, canola, and soybean.
- Omega-6 fats lower harmful LDL cholesterol and boost protective HDL. They also help keep blood sugar in check by improving the body's sensitivity to insulin. Good sources of omega-6 fats include safflower oil, sunflower oil, corn oil, soybean oil, sunflower seeds, walnuts, and pumpkin seeds.
Saturated fat. The term "saturated" means that the carbon atoms in a chain hold as many hydrogen atoms as they possibly can. This happens only when each carbon atom is connected to its carbon neighbors by single bonds. Without any twists, these straight chains can easily pack together. That's what makes saturated fats solids at room temperature. About two dozen different saturated fats exist in nature. They are abundant in meat and animal fat, dairy products, and in a few vegetables oils like palm and coconut oil.
Saturated fats suppress the body's ability to make receptors for low-density lipoprotein (LDL), a molecule that ferries cholesterol and other fats through the bloodstream. With fewer receptors available, levels of artery-harming LDL increase in the bloodstream. Different saturated fats have different effects on the artery-clogging process known as atherosclerosis. The saturated fats in butter and other dairy products most strongly increase LDL (bad) cholesterol. Those in beef fat aren't quite as powerful at boosting LDL, and those in chocolate and cocoa butter have an even smaller impact.
Trans fats. Heating polyunsaturated vegetable oil in the presence of hydrogen and finely ground particles of nickel metal causes hydrogen atoms to latch on to some—but not all—of the double-bonded carbons, changing them into single bonds. At the same time, some of the remaining double bonds twist into a new configuration, called the trans configuration, which gives the fat new chemical and physical properties. Partially hydrogenated fats don't spoil as easily as unsaturated fats, and can withstand being heated repeatedly, as in a restaurant deep-fat fryer.
Trans fats are worse for cholesterol levels than saturated fats because they raise harmful LDL and lower protective HDL. They fuel inflammation, a process that has been implicated in heart disease, stroke, diabetes, and other chronic conditions. They impair the flexibility of arteries and interfere with the ability of muscle and other tissues to respond to insulin. Even small amounts of trans fat in the diet can have harmful health effects. For every extra 2% of calories from trans fat daily—about the amount in a medium order of fast-food French fries—the risk of coronary heart disease increases by 23%. Eliminating trans fats from the U.S. food supply could prevent between 6% and 19% of heart attacks and related deaths, or more than 200,000 each year.
Selected resources: Fats
On the web
The Nutrition Source
Harvard School of Public health
This Web site, written by the Department of Nutrition at the Harvard School of Public Health, provides the latest information and advice about healthy eating, including the types and amounts of fats you should eat and which fats to avoid. You can also find recipes that use healthy fats and Harvard’s Healthy Eating Pyramid here.
This Web site is a gateway to nutrition information from a range of government sources. It includes links to the US Department of Agriculture (USDA) “My Pyramid,” a tool for creating individualized eating plans; the USDA National Nutrient Database for Standard Reference, where you can look up the calorie and nutrient content of thousands of foods; and the most recent version of the Dietary Guidelines for Americans, science-based advice about diet, physical activity, and health.
Face the Fats
American Heart Association
The American Heart Association (AHA) recommends that healthy people get 25% to 35% of total calories from fats. But which fats, and how many calories? This Web sites provides tools and information for making healthy fat choices when shopping, eating at home, or dining out. Of special interest: the “My Fats Translator” calculator, where you enter your age, gender, and activity level to get the number (and types) of fat calories you should aim for each day.
Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating
Walter C. Willett, M.D., with Patrick J. Skerrett
(Simon and Schuster, 2005)
This book provides current information on the links between diet and health, including the latest research on types of fats and their health effects. A large selection of recipes using heart-healthy fats is also included.