The three types of omega-3
Omega-3s are a family of polyunsaturated fats your body needs but cannot make in sufficient amounts, so you have to get them from food. Most of the research focuses on three: ALA, EPA, and DHA. Understanding the difference is the key to understanding the omega-3 benefits that follow.
ALA (alpha-linolenic acid) comes from plant foods like flaxseed, chia seeds, and walnuts. EPA and DHA are longer-chain omega-3s found mainly in seafood, and they are the forms tied most strongly to health benefits. According to the NIH, your body can convert ALA into EPA and DHA, but only in very small amounts, which is why seafood or an algae-based supplement is the most direct way to raise EPA and DHA levels.
Heart health and triglycerides
Cardiovascular health is where the evidence for omega-3s is strongest. The most consistent effect is on triglycerides, a type of blood fat that, when elevated, is associated with higher cardiovascular risk. A 2020 review of 23 studies with roughly 44,000 participants, summarized by the NIH, found that EPA and DHA reduce triglycerides by about 15 percent, with a larger effect in people who start with higher levels.
A review of 23 studies found that EPA and DHA reduce triglycerides by about 15 percent, with a stronger effect at higher baseline levels.
— National Center for Complementary and Integrative Health (NIH)
For broader heart outcomes, the American Heart Association recommends one to two servings of seafood per week to help reduce the risk of heart disease, stroke, and heart failure, particularly when the seafood replaces less healthy foods. The AHA notes that the protective evidence is stronger for people who already have coronary heart disease than for healthy individuals, and it does not recommend omega-3 supplements for people who are not at high cardiovascular risk. Where your own triglyceride and cardiovascular markers actually stand is something the DH360+ blood panel measures and an in-house MD reviews, so any dietary change is based on your numbers rather than a general guess.
Benefits beyond the heart
Omega-3s are marketed for a long list of other benefits, from mood to joints to brain health, and this is where careful reading matters. Some of these areas show promise, but the evidence is weaker and less settled than the cardiovascular findings.
Depression is a good example. A 2021 review of 35 studies, summarized by the NIH, concluded that if omega-3 supplements have an effect on depression, it may be too small to be meaningful, and the quality of the evidence was judged to be low. Omega-3s do play genuine structural roles in the body, including in cell membranes and the eyes, and research into areas like cognition and inflammation is ongoing. The honest summary is that heart benefits are well supported, while many other claims remain preliminary.
Best omega-3 foods
Food is the foundation, and the richest sources of EPA and DHA are cold-water fatty fish. Plant foods supply ALA, which is valuable but converts poorly to the forms that carry most of the benefit.
| Food | Main omega-3 | Notes |
|---|---|---|
| Salmon, mackerel, sardines, herring, tuna | EPA + DHA | Richest direct sources of long-chain omega-3s |
| Oysters and other shellfish | EPA + DHA (lower) | Some shellfish contain all three types |
| Flaxseed and flaxseed oil | ALA | One of the richest plant sources |
| Chia seeds, walnuts | ALA | Convenient plant-based options |
| Hemp seeds, edamame, fortified eggs | ALA (and some DHA) | Smaller, everyday contributions |
Common omega-3 food sources by type. Amounts vary by preparation and product. Sources: NIH Office of Dietary Supplements, Cleveland Clinic.
A practical way to meet the general seafood guidance is to build a couple of fish meals into your week and add a plant source most days. The example below is illustrative, not a prescription.
| Day | Omega-3 source |
|---|---|
| Monday | Ground flaxseed in oatmeal or a smoothie |
| Wednesday | Grilled salmon at dinner (seafood serving 1) |
| Friday | Walnuts as a snack |
| Saturday | Sardines or mackerel on toast (seafood serving 2) |
| Most days | Chia seeds added to yogurt or a smoothie |
Signs of omega-3 deficiency
True omega-3 deficiency is rare in the United States. According to the NIH, a deficiency of essential fatty acids can cause rough, scaly skin and a red, swollen, itchy rash. Because outright deficiency is uncommon, most people will not notice obvious symptoms.
The more common situation is falling short of the recommended EPA and DHA intake without a clinical deficiency, often simply because a person does not eat much fish. That gap does not usually produce dramatic signs, which is part of why intake is easy to overlook and worth being deliberate about through diet.
Supplements and knowing your levels
Supplements have a place, but they are not automatically the answer. The AHA's position is that most people should get omega-3s from seafood, with supplements reserved mainly for those with existing heart disease or high triglycerides and used under a physician's direction. Fish oil, krill oil, cod liver oil, and vegetarian algal oil are the common supplement forms.
The reason testing helps is that the decision to change your diet or add a supplement is most useful when it is tied to your own results. Different Health measures omega-3 status directly in its DH360+ blood panel, including EPA, DHA, and combined EPA+DHA+DPA, alongside cardiovascular markers like triglycerides, all reviewed by an in-house MD. From there, a team of MDs and PhDs interprets the numbers in the context of the rest of your assessment and builds any nutrition changes into a coached, personalized plan, with the option to retest and confirm the change is working.
Key takeaways
- Heart health leads: the strongest omega-3 benefits are cardiovascular, especially lowering triglycerides.
- Triglycerides drop measurably: the NIH cites a roughly 15 percent reduction from EPA and DHA, larger at higher baselines.
- Seafood first: the AHA recommends one to two servings of fatty fish per week, and does not recommend supplements for those without high heart risk.
- Plants help but convert poorly: ALA from flaxseed, chia, and walnuts turns into EPA and DHA only in very small amounts.
- Other benefits are unsettled: claims for mood and cognition remain preliminary, with weaker evidence.
- Deficiency is rare: outright omega-3 deficiency is uncommon, though many people still fall short of recommended EPA and DHA.
Frequently asked questions
What are the main benefits of omega-3?
The best-established omega-3 benefits relate to cardiovascular health. According to the NIH and American Heart Association, EPA and DHA lower triglyceride levels, and eating one to two servings of seafood per week is linked to lower risk of heart disease, especially when it replaces less healthy foods. Evidence for benefits beyond the heart, such as mood and cognition, is weaker and still under study.
What foods are highest in omega-3?
The richest sources of EPA and DHA are cold-water fatty fish such as salmon, mackerel, sardines, herring, and tuna. Plant foods including flaxseed, chia seeds, walnuts, and hemp seeds provide ALA, a different omega-3. Because the body converts ALA to EPA and DHA very inefficiently, seafood or an algal supplement is the most direct way to raise EPA and DHA levels.
What are the signs of omega-3 deficiency?
True omega-3 deficiency is rare in the United States. According to the NIH, a deficiency of essential fatty acids can cause rough, scaly skin and a red, swollen, itchy rash. Many people still fall short of the recommended EPA and DHA intake even without a clinical deficiency, which is why diet and, in some cases, testing matter.
Should I take an omega-3 supplement?
It depends on your diet and health. The American Heart Association recommends getting omega-3s primarily from seafood and does not recommend supplements for people without high cardiovascular risk. For people with existing heart disease or high triglycerides, supplements may be considered under a physician's direction. This is general information, not personal medical advice, so talk to your clinician.
Do omega-3s lower triglycerides?
Yes. A 2020 review of 23 studies with about 44,000 participants, summarized by the NIH, found that EPA and DHA reduce triglycerides by roughly 15 percent, with a larger effect in people who start with higher levels. Triglyceride-lowering is one of the most consistent and well-documented effects of omega-3s.
What is the difference between EPA, DHA, and ALA?
All three are omega-3 fatty acids. ALA comes from plant foods like flaxseed and walnuts and is the one your body cannot make. EPA and DHA are longer-chain omega-3s found mainly in seafood and are the forms tied most strongly to heart benefits. The body can convert ALA into EPA and DHA, but only in very small amounts.
References
- NIH Office of Dietary Supplements. Omega-3 Fatty Acids — Health Professional Fact Sheet.
- National Center for Complementary and Integrative Health (NIH). Omega-3 Supplements: What You Need To Know.
- American Heart Association. Omega-3 Fatty Acids for the Management of Hypertriglyceridemia (Science Advisory).
- Cleveland Clinic. Omega-3 Fatty Acids & the Important Role They Play.
- NIH Office of Dietary Supplements. Omega-3 Fatty Acids — Consumer Fact Sheet.