The Lowdown on Essential Omega-3 Fatty Acids in the Diet
The subject of scientific studies around the world, omega-3 fatty acids’ role in heart health is one of the most researched topics in nutrition. While that connection has long been established, omega-3 fatty acids, or omega-3s, also offer a long list of additional health benefits that warrant a closer look. To do so, it’s important to understand the basics — what are omega-3s, where can they be found and how much do we need to consume to reap these benefits?
Because omega-3 essential fatty acids cannot be made in the body, they must come from food. There are three types: eicosapentaenoic acid, or EPA, and docosahexanoic acid, or DHA (found in marine sources); and alpha-linolenic acid, or ALA (found in plant sources).
EPA plays a major role in supporting heart health and may help reduce inflammation in the body, while DHA, an integral part of cell membranes, plays a key role in brain development and function. The conventional understanding has been that ALA must be converted to EPA and DHA in the body to be effective; however, emerging science suggests factors including genetics, health status, gender and dietary habits — especially the amount of other fatty acids (see omega-6 sidebar) in the diet — can influence this conversion rate. Additionally, recent evidence suggests ALA may have health benefits of its own, independent of the conversion to EPA and DHA.
The Best Sources of Omega-3s
Fatty fish, such as salmon, is one of the most concentrated sources of EPA and DHA. However, the amount of omega-3s varies in wild versus farm-raised and among varieties of fish, such as Chinook or sockeye salmon.
To limit long-term exposure to contaminants and to maintain healthy and sustainable fish populations, choose from a variety of fish. Bluefin and albacore tuna, bluefish, black cod, rainbow trout and mackerel all deliver omega-3 fatty acids. Although they are often overlooked, herring, sardines and anchovies are affordable and sustainably sourced options.
Grass-fed meat and dairy products also naturally deliver small doses of omega-3s. In fact, some cattle ranchers are increasing the amount of omega-3s in animals they raise by feeding them marine algae or flaxseed.
Although it is debated whether omega-3 needs can be met with ALA sources alone, including them in the diet is a good move. Chia seeds, ground flaxseed and flaxseed oils, seaweed, soybeans and walnuts are all healthy additions to the diet. Vegetarians, vegans and anyone with a confirmed allergy to fish oil can supplement with microalgae to meet EPA and DHA needs. Microalgae is the original source of EPA and DHA, and is the primary food source for most fish, so algal oils deliver omega-3s without a fishy aftertaste.
At the supermarket, foods such as regular and non-dairy milk, peanut butter, yogurt, orange juice, margarine and eggs are sometimes fortified with omega-3s. Fortified foods may use marine algae, flaxseed oil or other sources to provide a combination of EPA, DHA and ALA. However, these foods provide small amounts of EPA and DHA, and rarely stack up to marine sources.
Omega-3s and Their Impact on Health
This alphabet soup of fatty acids provides significant health benefits. Higher blood levels of omega-3s are associated with heart-protective effects. Eating two to three servings per week of oily fish rich in omega-3s is associated with a lower risk of cardiovascular disease. Depending on the dose, fish oil — from supplements or fish itself — has been shown to modestly reduce blood pressure and reduce triglycerides by as much as 20 percent to 50 percent. For those with a history of heart attack, clinical and population research further suggests eating fatty fish may reduce the risk of death due to a heart attack by up to 9 percent.
Evidence regarding the effects of fish oil on depression and dementia is conflicting, and there’s insufficient evidence to support using fish oils for the treatment of Alzheimer’s disease. However, some studies on fish oil supplements show promise in slowing cognitive decline in those with very mild cognitive dysfunction. These outcomes depend on the dose and EPA to DHA ratio, and can vary depending on the population studied.
Beyond cardiovascular and brain health, research regarding the impact of omega-3s in the body is vast and includes a range of conditions. Population studies suggest young children who eat fish once or more per week have a lower risk of developing eczema. Although some research shows promise, more evidence is needed before health professionals can recommend using fish oils for treating dry eye, improving night vision in children with dyslexia or reducing pain episodes in patients with sickle cell disease.
While everyone must consume omega-3 fatty acids, individual needs vary with health status and diet. The American Heart Association recommends healthy adults eat fatty fish at least twice per week; the World Health Organization recommends 300 milligrams to 500 milligrams of EPA and DHA and 800 milligrams to 1,000 milligrams of ALA daily from food or a supplement. Those with a history of heart disease, heart attack or high triglycerides may further benefit from supplementation. Since there is no one-dose-fits-all approach, a registered dietitian nutritionist and health-care team can help clients determine specific needs.
How are Omega-6s Different from Omega-3s?
Like omega-3s, omega-6 essential fatty acids must come from food because the body cannot produce them. Omega-6s include linoleic acid, or LA, and gamma-linolenic acid, or GLA, found in vegetable oils, nuts and seeds; arachidonic acid, or AA, found primarily in animal fats, including fish; and conjugated linoleic acid, or CLA, found in ruminant meat, such as beef, and dairy.
Found naturally in sunflower, safflower, soy and corn oils, linoleic acid is the most highly consumed polyunsaturated fatty acid in the Western diet. There is concern that diets high in omega-6s may overload the enzymes required to convert the omega-3 ALA to EPA and DHA, thereby reducing the conversion rate. Most Americans consume plenty of omega-6s, so supplementation generally is unnecessary. In fact, the general advice to most people is to decrease their intake of omega-6s and increase omega-3s.
Science surrounding omega-6s and their effects on the body continues to emerge:
- One concern is that excess AA may increase inflammation in the body. However, research suggests this process doesn’t have the same effect on everyone, presenting a research opportunity to explore differences between those of European versus African descent, for example.
- Current research suggests GLA-rich evening primrose oil may be effective at reducing symptoms of diabetic neuropathy. Also, combined with fish oils and calcium, evening primrose oil seems to increase bone mineral density and decrease bone turnover in older adults with osteoporosis.
- There is evidence that, combined with other anti-inflammatory medications, omega-6-rich borage seed oil may reduce symptoms of rheumatoid arthritis by decreasing joint swelling and tenderness.
Omega-3 Supplementation and Safety
Because omega-3 food sources are limited and many Americans don’t eat the recommended two servings of fish per week, some people may need supplementation. When evaluating a supplement, ensure it includes both EPA and DHA, and look for certifications from independent testing organizations, such as NSF, to ensure it is high-quality and free of heavy metals and other contaminants.
Other than allergies, omega-3s from fish present few safety concerns. However, supplementing with fish oils in excess of 3 grams per day may increase the risk of excessive bleeding in people taking antiplatelet drugs, such as aspirin. In addition, supplementation may suppress the immune and inflammatory response in those with an immunodeficiency such as HIV/AIDS. Fish oils also can lower blood pressure levels, which may increase the effects of high blood pressure drugs. Taking 3 grams to 9 grams of fish oil per day has been shown to increase LDL blood cholesterol levels in some people. Like many things, more is not always better.
Contributing editor Marisa Moore, MBA, RDN, LD, is a consultant based in Atlanta and teaches nutrition at Georgia State University.