Omega-3 fatty acids: From fins and fish oil to flax
Omega-3 fatty acids are primarily found in fatty fish.
This article is part of an ongoing series entitled, Beyond Rx: OTC Corner, which will include topics such as OTC medications, dietary supplements, and other health care approaches that will help nurse practitioners and physician assistants provide patients with tools to manage their health.
Robert D. Sheeler, MD, is guest editor of the series. He is an associate professor of family medicine, Mayo Clinic, in Rochester, Minn. He is board certified in family medicine, integrative medicine, and holistic medicine.
Omega-3 fatty acids are a healthy subgroup of polyunsaturated fatty acids (PUFAs), the highest concentration of which is found in fish. Most of the PUFAs consumed in the Western world are proinflammatory omega-6 oils, which may be a contributing factor to many chronic diseases.
Omega-3 fatty acids
Omega-3 fatty acids are composed of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and are primarily found in fatty fish, krill, green-lipped mussels, and algae. Omega-3 fatty acids are considered "good" fats, and have both structural and anti-inflammatory roles in the body.
Plant sources of omega-3 fatty acids are predominantly derived from alpha-linolenic acid (ALA), which are primarily found in flaxseed, hemp, chia, canola, soy, pumpkin seed, and walnuts. ALA needs to be converted into omega-3 fatty acids in the body. The human body, however, can only convert a limited amount—in the range of 5% to 10% of plant-based ALA—into useful omega-3 fatty acids. Although both marine- and plant-based sources of omega-3 fatty acids are of value, the amount of useful omega-3 fatty acids that can be obtained from plant sources is limited by this necessary metabolic conversion.
Omega-6 fatty acids
Omega-6 fatty acids are proinflammatory oils, typically derived from vegetable oils and grains. Common food sources of omega-6 fatty acids are soybean oil, sunflower oil, and cottonseed oil. These oils lead to more arachidonic acid production and an increase in inflammatory mediators such as cyclooxygenase, lipoxygenase, leukotrienes, and glutamic acid, among others; this results in increased inflammation. Chronic inflammation is often associated with obesity, metabolic syndrome, diabetes, depression, arthritis, asthma, cardiovascular disease, and inflammatory bowel disease.1
The standard American diet has a ratio of omega-6 to omega-3 fatty acids that is approximately 20:1, which is significantly proinflammatory. Humans evolved with much lower ratios of omega-6 to omega-3 fatty acids in their diets. Some studies suggest an optimal ratio is approximately 5:1 or lower.2