Introduction
Omega-3 fatty acids are polyunsaturated fats that play many important roles in human health. As components of all cell membranes, they are concentrated in the brain and eyes. They can improve your heart, skin and hormone balance.
Our bodies obtain omega-3s from the foods we eat. If you don’t get enough of these fatty acids, the resulting deficiency can have negative impacts.
The most common omega-3 fatty acids are ALA, DHA and EPA. ALA (alpha-linolenic acid) is an essential fatty acid, meaning our bodies cannot make it and it must be obtained from food. ALA is found in plants such as flax seeds and walnuts. ALA has anti-inflammatory properties and may help in prevention and recovery from heart attack and stroke. The human body has the capacity to convert ALA into small amounts of DHA and EPA.
Although not essential fatty acids, DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) have been shown to have important roles in reducing inflammation, supporting cardiovascular health, and regulating mood and behavior. DHA is especially abundant in the brain and retina. It plays crucial roles in brain development, learning, memory and vision. DHA and EPA are found in the highest concentrations in fatty fish and fish oils.
Evidence suggests we should include both plant and fish sources in our diets to achieve beneficial levels of these three omega-3 fatty acids.
What omega-3 fatty acids do
Omega-3 fatty acids are an essential component of cell membranes, which are important for proper cellular function and communication. They are known to support brain, heart, eye and skin health. They also help lower chronic inflammation.
The brain is rich in omega-3 fatty acids, especially DHA. DHA is important for brain development and function, particularly in infants and young children. It plays a role in neurotransmitter signaling, brain cell communication and overall brain function.
DHA is also important for maintaining the structure and function of the retina, the light-sensitive tissue at the back of the eye. Adequate intake of omega-3 fatty acids may help prevent age-related macular degeneration, a leading cause of vision loss in older adults.
Omega-3 fatty acids are important for maintaining healthy skin. They help support the skin barrier function, regulate oil production and reduce inflammation, which can improve conditions like acne, eczema and psoriasis.
Omega-3s and health
Omega-3s may help lower the risk of developing heart disease, some forms of cancer, Alzheimer’s disease, dementia and age-related macular degeneration.
Heart disease
The strongest evidence for the benefits of omega-3 fats concerns the reduction of triglycerides. Omega-3 fatty acids can help lower triglycerides, blood pressure and inflammation. They may also raise protective HDL cholesterol. All these effects contribute to a reduced risk of heart disease and stroke. Studies show diets that include one 3-ounce serving of omega-3-rich fish per week have reduced risk. However, supplements have not been shown to have a protective effect.
Omega-3s have been shown to support immune function and play a role in regulating the body's inflammatory response by helping to reduce the production of pro-inflammatory compounds. This is important for managing chronic inflammatory conditions like rheumatoid arthritis, inflammatory bowel disease and asthma.
Cancer
Supplementation with EPA and DHA has shown promising benefits for women undergoing breast cancer treatment with chemotherapy. However, further research is necessary to evaluate the effectiveness of omega-3 when used with other therapies and to accurately assess the impact on patients' quality of life.
Mental health
Omega-3s have been studied in various mood disorders, such as postpartum depression, schizophrenia, Alzheimer’s and Parkinson’s. Omega-3 intake may slow cognitive decline by up to 20%. The most effective preparations appear to have at least 60% EPA relative to DHA.
Eye diseases
Since DHA is found in high concentrations in the retina of the eyes, deficiency may contribute to age-related macular degeneration, cataracts, glaucoma and diabetic retinopathy. Intake of DHA omega-3s may slow or prevent the development of age-related macular degeneration.
Some studies show improved outcomes with omega-3 supplements, especially when consumed with other antioxidants such as beta-carotene, lutein and zeaxanthin found in brightly colored vegetables.
Skin diseases
Omega-3s have strong anti-inflammatory effects on skin cells and can improve some skin conditions. These include psoriasis, dermatitis, allergic reactions and damage from UV radiation. Some studies show reduced incidence of skin cancer with omega-3 supplementation. Overall SCORAD (scoring in atopic dermatitis) scores were reduced with omega-3 supplementation.
Other
Maternal supplementation with omega-3s during pregnancy may protect children from developing allergies. Omega-3s’ anti-inflammatory properties may also help those with cystic fibrosis, rheumatoid arthritis and attention deficit hyperactivity disorder. Although evidence is inconclusive, moderate intake or supplementation has low risk and could be part of a healthy diet.
Omega-3 deficiencies
A deficiency in omega-3 fatty acids during critical periods of brain development, such as pregnancy and early childhood, may impair brain function, learning and memory. In adults, omega-3 deficiency has been associated with cognitive decline and an increased risk of neurodegenerative diseases like Alzheimer's.
With its role in vision development, DHA deficiency may increase the risk of age-related macular degeneration and other vision-related problems.
A deficiency in omega-3s may contribute to dry, flaky skin and an increased risk of skin conditions such as eczema and psoriasis.
Studies suggest a deficiency in omega-3s may increase the risk of heart disease by promoting higher levels of triglycerides, elevated blood pressure, increased inflammation and a tendency towards blood clot formation.
Deficiency may also lead to increased inflammation and risk for arthritis, skin disorders, inflammatory bowel disease and asthma.
How much do we need?
| Age | Male | Female | During pregnancy | During lactation |
|---|---|---|---|---|
| Birth to 6 months* | 0.5 g | 0.5 g | ||
| 7–12 months* | 0.5 g | 0.5 g | ||
| 1–3 years** | 0.7 g | 0.7 g | ||
| 4–8** | 0.9 g | 0.9 g | ||
| 9–13** | 1.2 g | 1.0 g | ||
| 14–18** | 1.6 g | 1.1 g | 1.4 g | 1.3 g |
| 19–50** | 1.6 g | 1.1 g | 1.4 g | 1.3 g |
| 51+** | 1.6 g | 1.1 g |
*Total Omega-3s. ** ALA only
From National Institutes of Health Office of Dietary Supplements. Omega-3 Fatty Acids Fact Sheet for Health Professionals
Food sources of omega-3
Fish and seafood sources
Seafood is one of the richest sources of DHA and EPA, which are the most biologically active forms of omega-3s. However, their content varies widely depending on the species.
| 3-oz. serving | DHA (g/serving) | EPA (g/serving) |
|---|---|---|
| Salmon, Atlantic, farmed, cooked | 1.24 | 0.59 |
| Salmon, Atlantic, wild, cooked | 1.22 | 0.35 |
| Herring, Atlantic, cooked | 0.94 | 0.77 |
| Sardines, canned in tomato sauce, drained | 0.74 | 0.45 |
| Mackerel, Atlantic, cooked | 0.59 | 0.43 |
| Salmon, pink, canned, drained | 0.63 | 0.28 |
| Trout, rainbow, wild, cooked | 0.44 | 0.40 |
| Sea bass, cooked | 0.47 | 0.18 |
| Tuna, light, canned in water, drained | 0.17 | 0.02 |
Plant sources
ALA is the only essential omega-3 fatty acid, meaning it must be supplied in daily dietary intake. Plant sources of omega-3 fatty acids provide a wide range of vitamins, minerals and fiber. ALA can be converted into small amounts of EPA and DHA.
Plant foods that contain ALA are excellent choices for those who are vegetarian, vegan, trying to lower their cholesterol or have allergies to seafood.
| Food source | Portion | ALA |
|---|---|---|
| Chia seeds | 2 Tbsp | 5 g |
| Walnuts | 1 oz | 2.6 g |
| Flax seeds | 2 Tbsp | 2.4 g |
| Hemp seeds | 3 Tbsp | 2.6 g |
| Firm tofu | ½ cup | 0.7 g |
| Avocados | 1/3 cup cubed | 0.5 g |
| Edamame | ½ cup | 0.3 g |
| Beans | ½ cup | 0.2 g |
| Spinach | 1 cup | 0.2 g |
| Oils | Portion | ALA |
| Flaxseed oil | 1 Tbsp | 7.3 g |
| Soybean oil | 1 Tbsp | 0.9 g |
| Canola oil | 1 Tbsp | 1.3 g |
Precautions
Risks with seafood
While seafood is a nutritious source of omega-3 fatty acids and various essential nutrients, there are some risks associated with its consumption.
Certain types of seafood — especially larger predatory fish such as shark, swordfish, king mackerel and tilefish — tend to accumulate higher levels of mercury. Mercury is a neurotoxin that can be harmful, particularly to the developing nervous systems of fetuses and young children.
Pregnant or nursing women and young children are advised to limit their consumption of high-mercury fish such as marlin, orange roughy, shark, swordfish, catfish and albacore tuna. Opt instead for lower-mercury alternatives such as salmon, Atlantic and Atka mackerel, sardines, light tuna or freshwater trout. Limit portions to no more than 12 ounces per week.
Some seafood, especially fatty fish from polluted waters, may contain persistent organic pollutants such as polychlorinated biphenyls (PCBs), dioxins and pesticides. These pollutants can accumulate in the fatty tissues of fish and may pose health risks if consumed in high amounts over time. Choosing seafood that is lower in contaminants and from cleaner waters can help mitigate this risk.
Despite these potential risks, seafood can still be a healthy part of a balanced diet when consumed in moderation and with attention to sourcing and preparation methods. Weigh the nutritional benefits against the potential risks and make informed choices based on your health and needs.
Supplements
Food sources of omega-3 fatty acids are preferred over supplements because they also provide vitamins, minerals and, in the case of plant sources, fiber. A wide range of omega-3 dietary supplements can be found in the form of fish oil, krill oil, cod liver oil and algal oil (a vegetarian source).
Supplements can interfere with prescription medications, increase the risk of bleeding or cause unpleasant side effects. Always speak to your primary care provider before considering supplementation.
Since supplements are not currently regulated by the Food and Drug Administration, it is important to choose a reputable source for omega-3 supplements. Supplements that contain oils can oxidize quickly, causing them to spoil. There is also some evidence to suggest that taking high amounts of oil-based supplements can be harmful. The FDA recommends a total of no more than 3 grams per day of omega-3 supplements.
Some studies point to the medical-grade omega-3 supplements as having a greater effect on lowering triglycerides. The FDA has approved these prescription forms for use in patients being treated for high triglycerides. Speak to your primary care provider if you have high triglycerides that may benefit from a prescriptive dose.
Best practices
- Seek out sources of the essential omega-3 ALA. Include 2 tablespoons of chia, flax or hemp seeds, or 1 ounce of raw walnuts daily as well as avocados, legumes and leafy greens for smaller amounts of ALA.
- EPA and DHA can be obtained from low-mercury seafood such as salmon, herring, sardines, Atlantic or Atka mackerel and light tuna. Aim for 3 to 12 ounces per week.
- If you are pregnant or nursing, get omega-3s from plant sources or low-mercury, low-contaminant seafood.
- Avoid medication interactions by consulting your primary care provider if you are taking blood thinners or medications to lower blood pressure.
- Research supplements to ensure reputable sourcing. Take no more than 3 grams of omega-3 supplements per day.
- Speak to your primary care provider about a purified, prescriptive dose of omega-3 to lower triglycerides.
References
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- National Institutes of Health Office of Dietary Supplements. Omega-3 Fatty Acids.
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- National Institutes of Health Medline Plus. Omega-3 fats – Good for your heart.
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- Sawada, Y., N. Saito-Sasaki and M. Nakamura M. 2020. Omega-3 fatty acids and skin disease. Frontiers in Immunology. 2021 Feb 5;11:623052.
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- National Institutes of Health Office of Dietary Supplements. Omega-3 Fatty Acids Fact Sheet for Health Professionals
- U.S. Department of Agriculture. FoodData Central
- U.S. Food and Drug Administration. Advice about Eating Fish
- Cleveland Clinic. Omega-3 fatty acids.
