Smart move: The healthy fats in olive oil are good for your brain as well as your heart.

How exactly do fats exert their effect on your brain and mood? A quick look at your brain tells suggests why healthy fats are so vital to healthy brain function. About 2/3 of the human brain is composed of fat. The cell membranes that surround neurons (nerve cells), and the myelin sheath around nerve fibers, are also made up of fat. Healthy cell membranes need to be supple and pliable to allow neurotransmitters (the chemical signals between brain cells) to flow in and out of the cells.

At room temperature, omega-3 fatty acids and alpha-linoleic acid (ALA) are liquid. They contribute to healthy, flexible cell membranes. Trans fats, on the other hand, tend to be solid and rigid at room temperature. These solid fats contribute to cell membranes that are relatively impermeable. They prevent the smooth flow of neurotransmitters in and out of brain cells, and they keep waste products trapped inside cells. They make it harder for blood vessels to dilate so that blood flows in and out of cells. In addition, trans fats contribute to inflammation, an immune response that further interferes with healthy brain function.

Olive oil is a good food source of healthy, unsaturated fats, and research shows it promotes healthy brain function. In addition to its beneficial effect on mood, it seems to help preserve cognitive function as we age. In one study, Italian senior citizens who consumed extra-virgin olive oil as their main dietary fat were less likely to experience age-related cognitive decline, compared with people who ate less olive oil. "It seems that in the aging process there is an increasing demand for unsaturated fatty acids," concluded Antonio Capurso, PhD, one of the researchers in that study.

Here are some ways to feed your brain with healthy fats:

• Jettison the junk food. Avoid processed foods, which typically contain trans fats. You can check food labels; look for "trans fats," "trans fatty acids," or "hydrogenated oil." But know that foods can contain a small amount of trans fats and still say "0 trans fats" on the package—and those small amounts can add up. These foods are bad for your heart as well as your brain and your mood.

• Eat a diet high in omega-3’s. Omega-3 fatty acids are found in fatty fish, such as salmon and omega-3-fortified eggs. You can also get omega-3’s from fish oil capsules. Rodale.com recommends fish that's responsibly harvested, such as Alaska wild salmon, and organic eggs.

• Pour on the olive oil. Use olive oil whenever you can. Try lots of recipes with olive oil and leafy greens for extra heart protection.

• Look at labels and avoid foods with hydrogenated fats. As mentioned, processed foods may contain trans fats even if the label doesn't say so. You're better off eating healthier food, and when you have to have to indulge your sweet tooth, finding food made without hydrogenated or trans fats. See our story on misleading food labels to help you navigate the supermarket shelves.

• Consume foods that are high in monounsaturated fats. There are plenty of ways to enjoy these healthy, brain-boosting fats. Options include avocados, peanuts, walnuts, almonds, pecans, mackerel, salmon, and herring.

Jeffrey Rossman, PhD, is director of life management at Canyon Ranch in Lenox, MA, and the author of The Mind-Body Mood Solution: The Breakthrough Drug-Free Program for Lasting Relief from Depression (Rodale Press, 2010).