The A to Z of essential fatty acids
She’s fast, she’s lean, she looks amazing. Who would guess she thinks of fat as a friend?
But when you’re a fitness coach, triathlon trainer and vegetarian like Selene Yeager, you always look for every good source of fuel you can find. So Yeager makes sure to consume a good measure of dietary fat to keep her cells and tissues healthy, lubricated and in good repair.
That fat helps Yeager answer to a demanding body. Start with 100 miles of biking and 20 miles of running every week. Throw in several miles of swimming, and you have the "tri" in triathlete. By week’s end, Yeager knows in her bones why consuming healthy fats is an important part of her vegetarian lifestyle.
"I don’t run into the problems that other athletes do," says Yeager, a 34-year-old writer, editor and mother who lives and works in Emmaus, Pennsylvania. "I don’t have overuse injuries. My cartilage seems to be very healthy. I recover well, and I don’t get sick after athletic events. And I think a lot of that has to do with eating the right fat."
As a student at Pennsylvania State University, when she took her first steps as both athlete and vegetarian, Yeager could not imagine that fat in her diet could be important. After all, "fat" used to be a bad word, classic shorthand for heart disease, cancer and a host of other health problems.
But nutritional experts have learned that some dietary fats—and the acids that make up those fats—are essential to our systems. Because our bodies don’t manufacture them, they must be obtained from food. These essential fatty acids (EFAs) help keep arterial walls well-lubricated, boost the immune system, reduce inflammation and help the body absorb important vitamins.
The author of The Doctors Book of Food Remedies, Yeager first learned about the benefits of essential fats on a recent trip to Italy. There she learned that a Mediterranean diet rich in foods such as olives and avocados—packed with heart-healthy, brain-boosting fatty acids—had helped Greeks, Italians and others native to that region stay healthy and maintain a consistent weight. "It all just came together that you could really eat 40 percent of your diet in fat and not crack another notch on the scale," says Yeager. "In fact, you’d probably lose weight and feel better."
The trick is in balancing fats from a variety of foods. All foods that contain dietary fat contain a combination of fatty acids—the chemical building blocks of fat. Learning about the mixture of fatty acids in your diet will help you figure out how to choose foods with the good fats and avoid those foods that contain the bad fats.
That means doing a bit of simple chemistry homework before heading off to the grocery store. Dietary fats are composed of four different types of EFAs with names that may sound familiar to any modern consumer: saturated, trans fatty, monounsaturated and polyunsaturated. Their names were devised to reflect their chemical properties—how many carbon and hydrogen atoms each fatty acid contains and how they happen to be arranged along the acid’s carbon "backbone."
In general, the more saturated the fatty acid, the more hydrogen is usually present, which makes the fat more difficult for the body to break down and use. That’s why saturated fats—found mainly in red meat, dairy products and coconut and palm oil—have long been considered unwelcome guests at the table. In particular, saturated fat raises the level of low-density lipoprotein (LDL), or "bad" cholesterol, and clogs arteries.
But trans fatty acids are quickly replacing saturated fatty acids as the villains of the dietary fat world. Trans fats rarely occur naturally; rather, they are produced almost always through the process of hydrogenation, a manufacturing process that food chemists use to inject hydrogen into fatty acids to harden a vegetable oil—margarine, for example. Hydrogenation also appears to extend shelf life.
Trans fatty acids not only raise LDL levels, they also lower high-density lipoprotein (HDL), or "good" cholesterol, in the blood. "These fats aren’t useful—the human body doesn’t know what to do with them," says Brian Olshansky, MD, Director of Cardiac Electrophysiology and Professor of Medicine at the University of Iowa Hospitals in Iowa City. "They stiffen up the membranes in the body everywhere—in the linings, the blood vessels, all the cells that cover your nervous system."
Packaged foods such as potato chips, peanut butter and many margarines are full of trans fats. "The worst kinds of trans fats are located in things such as french fries, doughnuts and artificial cheese in pizza," says Olshansky. "Trans fats are in almost all the processed foods we eat. Just about anything you buy, especially from fast food places, is just loaded with them."
For healthy fats, look instead to monounsaturated and polyunsaturated fatty acids. These are the fats common to the Mediterranean diet that occur naturally in a variety of vegetables, oils and nuts. The monounsaturated fatty acids found in olive oil, avocados and almonds, for example, tend to resist attack from free radicals—specially formed types of atoms that can damage your body’s cells when they react with DNA or cell membranes—better than other fats and thus are less prone to stick to your arteries.
Polyunsaturated fats occur in food either as omega-3 or omega-6 fatty acids—chemical names that refer to precise juxtapositions of carbon and hydrogen atoms. The key to eating healthy polyunsaturated fats is to maintain the right balance of omega-3 acids—found abundantly in flax, walnuts and canola oil-with omega-6 acids, found in vegetable oils such as corn, safflower and sesame.
Researchers note that consuming too many omega-6 fatty acids, especially the alpha-linolenic acid (known as ALA or LNA) found in meat, can lead to blood clotting and cancer cell growth, particularly in the prostate. "We need omega-6 fats, and we certainly don’t want to eliminate them from our diet," says Norman Salem, PhD, senior investigator for the Laboratory of Membrane Biochemistry and Biophysics at the National Institute on Alcohol Abuse and Alcoholism (NIAAA), National Institutes of Health (NIH). "But in the American diet, we’re getting 17 grams per day of linolenic acid, which is probably an overdose."
Omega-3 fatty acids may also benefit mental health. Besides noting how omega-3 acids appear to reduce blood clotting, inflammation and the overall risk of coronary disease, scientists have begun to study how two key components of omega-3-eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)-may help combat clinical depression, bipolar disorder and schizophrenia.
A 1998 NIH study conducted by one of Salem’s colleagues, Joseph Hibbeln, MD, chief of the NIAAA’s outpatient clinic, showed a link between low rates of depression and the consumption of large amounts of dietary omega-3s.
Another study by Hibbeln, reported in the July 2002 issue of Journal of Affective Disorders, indicated that increased levels of EPA and DHA may also help alleviate the effects of postpartum depression. This is especially important for vegetarians, the researchers say, because a low consumption of omega-3s may cause vegetarian women to be deficient in these essential fats before they become pregnant. "It’s been known for a while that there’s some depletion of DHA in mothers," says Salem. "And in vegetarians, there’s already a decreased level of DHA suggested by studies of maternal and infant circulation."
Unfortunately for vegetarians, fish is the primary source of EPA and DHA. But the good news is that the body converts EPA and DHA from the healthy ALA in plant sources. (See the sidebar "Sources of Dietary Fats.") DHA supplements made from algae-though difficult to find-are available for those rare cases in which the body cannot manufacture its own DHA.
"Essential fatty acids are available in so many places," notes Anita Sandretto, PhD, Director of Human Nutrition at the University of Michigan School of Public Health. "All of the vegetable oils are readily available, and all of them will give you essential fatty acids."
For Selene Yeager, embracing the basics of a Mediterranean diet has brought a kind of nutritional balance that’s paying off in her athletic competitions. "I started eating more olives, olive oil and avocados, and—lo and behold—I felt more full and had even more energy," she reports. "I perform much better today, and my weight stays very steady."
Yeager felt so good, in fact, that only 12 weeks after giving birth to her daughter, Juniper, in April 2002, she raced in the Anthracite Tri Olympic distance triathlon in Jim Thorpe, Pennsylvania—and won her age group. She says, "I’m convinced that smart eating all the way through and after my pregnancy was a big part of that."