Omega-3 fatty acids are one of two types of polyunsaturated fatty acids. Due to their anti-inflammatory properties, omega-3 fatty acids are considered the healthier type.
Omega-3 fatty acids are found in fish, seafood, and some plant-based foods like flaxseed. There are several types of omega-3s, but the most common ones used in research are known by their initials: ALA (alpha-linolenic acid), DHA (docosahexaenoic acid), and EPA (eicosapentaenoic acid).
ALA is an essential fatty acid, meaning you can only get it from food. The body can convert ALA into EPA and DHA but in very limited amounts. Omega-3 fatty acids are promoted for many health benefits, but only some of these benefits have strong research to support their use.
Supplement Safety
In the United States, the Food and Drug Administration (FDA) does not regulate dietary supplements the way it does for prescription medications. As a result, some supplement products may not contain the ingredients listed on the label.
When choosing a supplement, look for products independently tested or certified by organizations such as NSF.org, U.S. Pharmacopeia (USP), and ConsumerLab.com. For personalized guidance, consult your healthcare provider, registered dietitian nutritionist (RD or RDN), or pharmacist.
1. May Reduce Risk of Cardiovascular Death
Large and long-term prospective randomized clinical trials, including VITAL, ASCEND, REDUCE-IT, and STRENGTH, have examined the effects of omega-3s on reducing the risk of death from heart disease.
In the trials, omega-3 supplements (EPA and DHA) helped reduce the following:
- Heart attack rates, especially among individuals who do not consume enough omega-3s in their diet
- Rates of cardiovascular events (e.g., heart attack, stroke) by 25%
- Risk of cardiovascular death
Another meta-analysis that included the above trials and others found that omega-3 supplementation reduced the risk of heart attack and mortality associated with coronary heart disease (CHD) and cardiovascular disease (CVD).
Moreover, an article in the Cochrane Database of Systematic Reviews concluded that omega-3 supplementation slightly reduces the risk of CHD events and mortality.
Based on the evidence, experts recommend the following:
- The American Heart Association (AHA) advises consuming one or two servings of seafood weekly to reduce the risk of CHD.
- For those with existing CHD, consume 1 gram per day of EPA and DHA, preferably from fish, but you may consider supplementation under the guidance of a healthcare provider.
- The Dietary Guidelines for Americans recommends 8 ounces of fish per week to reduce the risk of CVD and CVD events, such as a heart attack.
The FDA approved the health claim for omega-3 fatty acids confirming supportive, but not conclusive, evidence that EPA and DHA may reduce the risk of CHD. The dietary supplement labels for omega-3s should not recommend taking more than 2 grams daily.
Prescription Fish Oil
The REDUCE-IT trial studied a high-dose prescription fish oil supplement. It was dosed at 4 grams per day. The results found that this dose reduced high levels of triglycerides (fat in the blood) and provided a 25% reduction in CVD events like heart attack or stroke.
This study led to the fish oil supplement becoming an approved prescription treatment. It is now marketed as Vascepa, which has a recommended dose of 4 grams daily.
2. May Improve Cholesterol Levels
Conditions that are considered risk factors for CVD include high blood pressure (hypertension), high cholesterol levels (hyperlipidemia), obesity, and type 2 diabetes. Some of these conditions are also components of metabolic syndrome (a group of conditions that together increase the risk of diabetes, stroke, and heart disease).
Omega-3 fatty acid supplementation has been studied in people with obesity, metabolic syndrome, and diabetes. Research has found that, compared to placebo, omega-3s helped:
- Reduce total cholesterol (a measure of the total amount of cholesterol in the body, including low-density lipoprotein cholesterol, triglycerides, and high-density lipoprotein cholesterol)
- Reduce triglycerides
- Increase high-density lipoprotein cholesterol, also known as "good cholesterol"
Reducing or eliminating risk factors associated with CVD can help improve health outcomes. Discuss your risk factors and ways to manage risk with your healthcare provider.
3. May Lower Blood Pressure
In addition to its cholesterol-lowering effects, omega-3 supplements have demonstrated a potential in reducing blood pressure in clinical studies.
According to four trials evaluated as part of a larger meta-analysis, taking omega-3 supplements was associated with a significant decrease in systolic and diastolic blood pressure in people with metabolic syndrome. Systolic blood pressure is the amount of pressure in the arteries while the heart is beating, while diastolic is the amount of pressure while the heart is resting.
In other studies, ALA supplementation lowered blood pressure in people with obesity or overweight.
Managing your risk factors for heart disease should include a combination of dietary modifications, physical activity, and any medications prescribed by your healthcare provider. Supplementation alone will not be enough to improve your heart health.
4. May Reduce Inflammation
Inflammation can be acute (your body's sudden, natural response to injury or illness) or chronic (persists for a long time without injury or illness). Chronic inflammation contributes to chronic illness.
Inflammation can be detected through blood tests. Common blood tests that are markers of inflammation include C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-a).
Research has found that omega-3 supplements have:
- Reduced CRP and IL-6 levels in people with CHD
- Reduced IL-6 and TNF-a in people with cancer
- Reduced TNF-a levels in people with diabetes
Further research is needed to determine the full effects of these benefits.
5. Supports Fetal Growth in Pregnancy
DHA is an important nutrient during pregnancy that promotes the growth and development of the fetus. Studies have shown it can slightly increase birth weight and reduce preterm births.
The Dietary Guidelines for Americans recommends pregnant people consume 8 to 12 ounces of fish per week to get enough DHA. Fish like salmon, herring, sardines, and trout are great sources of omega-3s and do not contain excessive amounts of mercury.
If you're unable to eat fish, omega-3 supplementation during pregnancy may offer some benefits. One meta-analysis found that supplementing with 450 to 800 milligrams of DHA per day reduces the risk of preterm births and can increase birth weight.
How Much Omega-3 Should You Take Per Day?
Unproven Uses
Omega-3 fatty acids are promoted for several other health conditions. For the following, the research is either inconsistent to fully support the use of omega-3s or is still in preliminary stages:
- Behavioral regulation in attention deficit hyperactivity disorder (ADHD): Some preliminary data suggest that omega-3 supplementation may improve parent-rated emotional lability (rapid changes in mood noted by parents) and oppositional behavior, but further research is still needed.
- Cancer prevention: Study results have been mixed. The VITAL study compared 1 gram per day of EPA and DHA to placebo, showing no difference in cancer incidence between the two groups. However, some data show that omega-3 intake may reduce breast cancer risk, and fish intake may reduce colorectal cancer risk.
- Childhood allergies: Limited data support supplementing omega-3s during pregnancy and breastfeeding to reduce the risk of allergic diseases in the child.
- Cognitive decline: Results on omega-3's impacts on cognition (mental processes responsible for acquiring, storing, and using knowledge) have been mixed. In a meta-analysis, DHA supplements improved cognition in some studies but had no effect in others. Moreover, there were no benefits seen for those with Alzheimer's disease.
- Depression: Omega-3s are thought to improve depression symptoms. While they may play a role when used along with medication, studies did not find enough evidence to support omega-3 supplementation for this purpose.
- Eye health: A high fish intake is associated with a reduced risk of age-related macular degeneration (AMD). However, supplementing omega-3s has not shown benefit. Additionally, using omega-3 supplements for dry eye disease has had inconsistent results.
- Infant brain development: Clinical trials and systematic reviews have not found conclusive evidence that omega-3 supplementation during pregnancy improves cognitive and visual development in infants. However, DHA is now added to most infant formulas and some milk products.
- Rheumatoid arthritis (RA) symptoms: Research on the use of fish oil supplements for RA has had mixed results. A recent meta-analysis has suggested limited benefits of omega-3 supplementation for lowering disease activity.
Risks of Taking Omega-3
Fish oil supplements can have a fishy aftertaste. Other reported side effects include nausea, bloating, and burping. Always discuss the potential risks and side effects of omega-3 supplements before starting them.
Other risks of taking omega-3 supplements include:
- Atrial fibrillation: Some data suggests an increased risk of developing atrial fibrillation (a heart rhythm disorder) in those with elevated CVD risk who take omega-3 supplements.
- Bleeding: Taking more than 3 grams per day of omega-3 fatty acids can increase your risk of bleeding.
- Prostate cancer: Some (but not all) research suggests that higher blood levels of omega-3s increase the risk of prostate cancer.
- Drug interactions: Omega-3 supplements may interact with blood pressure-lowering medications (e.g., beta-blockers) and blood thinners (e.g., warfarin).
Summary
Omega-3 fatty acids can easily be obtained by eating a healthy and balanced diet that includes seafood.
Alpha-linolenic acid is found in plant-based food products like flaxseeds, chia seeds, and walnuts. It is also found in flaxseed, canola, and soybean oils. Fish and seafood like salmon, herring, sardines, mackerel, trout, and oysters are good sources of DHA and EPA.
Omega-3 supplements are available for those who cannot get these fats through their diet or those for which supplements offer an added health benefit. Omega-3 supplements can improve heart health, and high doses can lower triglyceride levels. Other benefits are not conclusive.
Before starting a daily supplement, you should speak with your healthcare provider to be sure they are of benefit to you.
