Omega-3: why fish instead of flax?

Omega-3 fatty acids can have many health benefits, but the way you consume them makes a difference. If you are interested in eating more omega-3s, be sure to pay attention to the type you eat, as well as your intake of omega-6s.

Types of Omega-3 Fatty Acids and Conversion Factors

Omega-3 fatty acids exist in many forms, including eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and alpha-linolenic acid (ALA). EPA and DHA are found in fatty fish and fish oils, while ALA is abundant in walnuts, flax, chia, hemp, and their oils.

Research links EPA and DHA consumption to a number of health benefits related to the prevention of inflammatory diseases. On the other hand, ALA is mainly used as an energy source for the body, and does not appear to have as strong of an anti-inflammatory effect as EPA and DHA (1). The body can convert ALA to EPA and DHA, but the conversion is inefficient. Depending on a number of factors, women may be able to convert up to 21% of ALA to EPA and 9% to DHA, while men can only change up to 8% of ALA to EPA and less than 4% to DHA (2).

That being said, foods high in ALA still have wonderful nutrients. One ounce of chia seeds gives you 11 g of fiber, and a healthy dose of calcium (18% of your DV!) (10). ALA is also an essential nutrient, meaning the body cannot produce it and you must obtain it from your diet. ALA provides a number of health benefits for the heart and nervous system (11). As you can see, ALA should be part of a healthy diet, but should not be the sole source of omega-3s if you want to reap the benefits of EPA and DHA, too.

The Role of Omega-6 Fatty Acids

The inefficient conversion of ALA to EPA and DHA gets even more complicated with excessive consumption of omega-6 fatty acids, found in vegetable oils, such as corn, soybean, and safflower, and almost all processed foods. One study found that the conversion of ALA to EPA and DHA decreased as much as 54% when dietary intake of omega-6s increased from 15 grams, the average daily intake by Americans, to 30 grams/day in human participants (23). Omega-6s have this effect because the liver uses the same pathway and enzymes to process omega-6s as it does to convert ALA to EPA and DHA (2).

Balance is Key: The Omega-6/Omega-3 Ratio

As you can see, too many omega-6s can diminish the impact of omega-3s in the body, especially if you rely on plant-based ALA for your only omega-3 intake and/or do not consume much EPA and DHA. Even more, excessive omega-6 intake, along with limited omega-3 consumption, may have pro-inflammatory effects in the body. Inflammation related to increased omega-6s is linked to chronic illnesses that are often associated with the Western diet, such as heart disease, cancer, asthma, and autoimmune conditions (4, 5, 67, 8, 9).

A number of scientists and nutrition researchers emphasize that our ancestors evolved on a ratio of omega-6 to omega-3 close to 1:1 or 2:1. Today, the average American consumes a ratio between 15 and 25:1 (4, 5). This is due to the rampant use of vegetables oils, such as corn and soybean, in processed foods and restaurant meals, and the increased consumption of these foods. Keep in mind, omega-6s are necessary for certain processes, and can have positive influences on disease states when consumed in the correct balance. So, it is important to think of your fatty acid intakes as a ratio, rather than focus on the specific amounts of each.

The omega-6/omega-3 ratio is one of the hottest debates in the nutrition world. More research on the correct ratio for optimal health, as well as the implications of achieving this ratio on disease reduction, is needed.

Based on current knowledge, we can all stand to reduce our consumption of omega-6 fatty acids and eat more omega-3s, especially in the forms of EPA and DHA. The best way to decrease vegetable oil consumption is to cook with olive oil, and to swap processed foods with whole foods! For recipe inspiration, click here.