Omega-3 Fatty Acids and Plant-Based Diets

Omega-3s are essential fatty acids. They play an important role in cellular function and in maintaining heart health, brain health, kidney function, eye health, and skin health.

Omega-3 fatty acids are readily available in a wide variety of plant foods. Sources include walnuts, flaxseed, chia seeds, hemp seeds, edamame, seaweed, and algae. Other green leafy vegetables and beans also contain small amounts. 

Plant-derived omega-3s come in the form of alpha-linolenic acid (ALA)—which is the only essential omega-3 fatty acid. Our bodies cannot synthesize it, so we must consume ALA through our diets. The body naturally converts ALA into the longer-chain omega-3 fatty acids docosahexaenoic acid (DHA)—which is important for brain health—and eicosapentaenoic acid (EPA).

Fish contain both DHA and EPA. But that doesn’t mean that individuals following plant-based diets are deficient in these longer-chain omega-3s. In fact, women following vegan diets actually had significantly more long-chain omega-3 fats in their blood, compared with fish eaters, meat eaters, and ovo-lacto-vegetarians, according to findings from the European Prospective Investigation into Cancer and Nutrition (EPIC) Study.¹ Despite zero intake of long-chain omega-3s (EPA and DHA) and lower intake of the plant-derived ALA, vegan participants converted robust amounts of shorter-chain fatty acids into these long-chain fatty acids, compared with fish eaters.

Most people following plant-based diets have no problem getting enough omega-3s in their diets. One study found that people who follow vegan diets, on average, have intakes above the recommended amounts for omega-3 fats.²

When it comes to measuring omega-3 levels, the likelihood of having lower EPA and DHA levels among vegans is, on average, higher; however, this does not extend to any known clinical relevance. In fact, researchers note the advantage of a vegan diet for heart health compared with a nonvegan diet.³

Another benefit plant-based eaters may have is a more desirable ratio of omega-6 to omega-3 fatty acids compared with a Standard American Diet. Omega-6 fatty acids are known as the pro-inflammatory fats, whereas omega-3 fatty acids are known as the anti-inflammatory fats. The desired ratio of omega-6 to omega-3 is 4:1; however, most Americans are consuming a ratio of 20:1, which can lead to excess inflammation in the body. The Standard American Diet consists of excessive amounts of foods rich in omega-6 fatty acids, such as processed and fast foods, and foods containing safflower oil, sunflower oil, corn oil, and soybean oil. Therefore, people eating diets rich in whole, plant-based foods may have a more adequate ratio of omega-6 to omega-3.⁴

Plant-based foods are beneficial to the brain and may help prevent Alzheimer’s disease and other forms of dementia. Although omega-3s are important for brain health, optimal brain health is about more than omega-3 intake. Research shows that saturated and trans fats—found in animal products, pastries, and fried foods—can increase the risk for cognitive decline.⁵ Foods rich in vitamin E—including nuts, seeds, leafy greens, and whole grains—are especially beneficial for brain health. Studies have also suggested that vitamin C—found in fruits and vegetables—may help protect against cognitive decline.⁶

Although some of the fat found in fish comes in the healthy omega-3 form, much of the remaining fat is unhealthful saturated fat. For example, chinook salmon derives 52% of its calories from fat, a quarter of which is saturated fat. Fish and shellfish are also significant sources of cholesterol. Three ounces of bass has about 80 milligrams of cholesterol—the same amount found in a 3-ounce steak. Diets high in saturated fat and cholesterol can increase the risk of heart disease.

On the other hand, a plant-based diet has been proven to prevent, and even reverse heart disease. One study found that while replacing red meat with plant-based protein lowers the risk for heart disease, replacing red meat with fish did not reduce the risk.⁷ In another study comparing a Mediterranean diet, which is known to be high in fish and omega-3 fats, to a vegan diet, the low-fat vegan diet had a larger improvement in body weight and cholesterol.⁸

Although fish oil supplements have been touted as a cure for everything from heart problems to arthritis, current research shows that there may not be any benefits to taking the supplement. According to a review that combined data from 20 studies, the use of omega-3 supplements over a two-year period had no effect on heart-related death, heart attack, or stroke.⁹ Further research found no link between fish oil supplements and the prevention or improvement of dementia.^10,11

By focusing on plant foods like vegetables, fruits, whole grains, and legumes, you’ll get the full range of essential nutrients without the toxins and other health risks associated with fish consumption.¹²

Work with your physician if you are considering or starting an omega-3 supplement. Omega-3 supplementation may be advised for those with increased needs, such as pregnant and lactating women, elderly individuals, and those with certain chronic diseases. Consider algae-based DHA and EPA supplementation if you are concerned you are not getting enough from food.