According to a study published in The New England Journal of Medicine, people who followed a diet emphasizing poultry and fish (aka “the National Cholesterol Education Program Step II Diet”) found that their cholesterol levels changed very little.

The reason for these unimpressive results is no mystery. Fish flesh contains plenty of cholesterol and fat, just as beef does. Of the fat found in fish, about 15 to 30 percent is saturated fat. This is a lower percentage than the amount of saturated fat found in beef and chicken, but it is still much higher than truly low-fat vegetarian foods.

Fish often carry contaminants from polluted waterways. About 40 percent of fish samples have so much bacterial contamination that they have already begun to spoil before they are sold. Fish are also often contaminated with PCBs, which have been linked to cancer and birth defects. Consumer Reports found PCBs in 43 percent of salmon, 50 percent of whitefish, and 25 percent of swordfish. The U.S. Food and Drug Administration and the Environmental Protection Agency have warned pregnant women, women who may become pregnant, breastfeeding women, and children to limit their consumption of fatty fish flesh because it contains mercury, which can contribute to birth defects, kidney damage, impaired mental development, and even cancer. According to an article in the Chicago Tribune, “Almost all the mercury that people are exposed to comes from eating fish.” The article also states: “Mercury can damage the central nervous system of children, causing subtle delays in walking and talking as well as decreased attention span and memory. Adults can experience headaches, fatigue, numbness in the hands and feet, and a lack of concentration.”

But what about those much-touted essential fatty acids found in fish-the omega-3s?

While omega-3 essential fatty acids can reduce the blood’s level of triglycerides (which play a role in heart disease), the omega-3s found in fish are highly unstable. They tend to decompose and unleash dangerous free radicals, which are linked to cancer, arteriosclerosis, and premature aging.

According to researchers at the University of Arizona, the omega-3s found in vegetables—including walnuts, pecans, flaxseeds, broccoli, spinach, and soybeans—are more stable than those found in fish. In addition, plant-based omega-3s are often coupled with antioxidants, which can help neutralize those free radicals that are produced. Plus, plant-derived omega-3s don’t have the fishy odor that is sometimes present in the perspiration of people who take fish oil.

If you really want to work on beating heart disease, forget the fish and try a vegan diet that is rich in fruits, vegetables, whole grains, and beans and low in oils of any kind. You may also want to try vegan supplements made from microalgae that contain DHA, one of the omega-3 fatty acids found in fish. (Brands include DEVA Nutrition, Sea Vegg, NuTru, and Dr. Fuhrman’s.) They do your heart good—without the dangerous toxins.

Alisa Mullins is a senior writer at People for the Ethical Treatment of Animals (PETA). To learn more about Alisa, click here. For more information about PETA, call 757-622-7382 or email PETAPrime@peta.org.