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Omega-3 Fatty Acids

Table of Contents

What omega-3 fatty acids actually do
How EPA and DHA work in the body
Brain health across the lifespan
Sources and supplementation

What omega-3 fatty acids actually do

Omega-3 fatty acids are polyunsaturated fats your body cannot produce on its own. The three main types are alpha-linolenic acid (ALA) from plants like flaxseed and walnuts, and the two marine-derived forms: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Here is the catch—your body converts ALA to EPA and DHA at a rate below 5%, so getting EPA and DHA directly from fatty fish, seafood, or algae-based supplements is practically essential ^[1].

How EPA and DHA work in the body

EPA and DHA embed themselves into cell membrane phospholipids, where they alter membrane fluidity, receptor function, and cellular signaling. EPA serves as the primary building block for resolvins and protectins—specialized pro-resolving mediators that actively terminate inflammatory cascades rather than merely suppressing them ^[2]. DHA constitutes roughly 40% of the polyunsaturated fatty acids in the brain and 60% in the retina, making it structurally essential for neurological and visual function throughout life.

Cardiovascular protection

The cardiovascular evidence for omega-3s ranks among the strongest in nutritional science. EPA and DHA reduce triglycerides by 15-30% at doses of 2-4 grams daily, lower resting heart rate, improve arterial elasticity, and decrease platelet aggregation. The landmark REDUCE-IT trial demonstrated that 4 g/day of purified EPA cut major cardiovascular events by 25% in statin-treated patients with elevated triglycerides ^[3]. A 2025 meta-analysis of 42 studies covering 176,253 participants confirmed that omega-3 supplementation significantly reduces cardiovascular mortality, coronary heart disease events, and myocardial infarction risk ^[1].

Brain health across the lifespan

DHA is critical for neurodevelopment during pregnancy and early childhood, but its benefits extend far beyond. Higher omega-3 index values correlate with larger hippocampal volumes and better cognitive performance in older adults. Some research suggests omega-3s may protect telomere length, a marker of cellular aging, though these findings require confirmation in larger trials. The most consistent longevity signal comes from maintaining an omega-3 index of 8% or higher ^[4].

Inflammation and immune function

Beyond cardiovascular and neurological benefits, omega-3 fatty acids modulate immune responses. EPA-derived resolvins actively resolve inflammation rather than simply blocking it ^[2]. This mechanism explains why omega-3 supplementation shows promise in conditions characterized by chronic inflammation, from rheumatoid arthritis to depression.

Sources and supplementation

Fatty fish like salmon, mackerel, sardines, and anchovies provide the most concentrated dietary sources of EPA and DHA. For those who do not consume fish regularly, supplements offer an effective alternative. The omega-3 index test provides a reliable way to assess your status and track improvement over time ^[1].

References

Test your omega-3 index

A simple dried blood spot test measures the percentage of EPA+DHA in your red blood cell membranes. Aim for 8-12%, which is associated with the lowest cardiovascular and all-cause mortality risk.

pubmed.ncbi.nlm.nih.gov

Choose triglyceride-form supplements

Triglyceride-form fish oil is absorbed up to 70% better than ethyl ester form. Check the label or contact the manufacturer if it's not clearly stated. IFOS 5-star certification ensures purity and low oxidation.

Take omega-3s with a fat-containing meal

EPA and DHA absorption improves significantly when taken alongside dietary fat. Taking your supplement with your largest meal of the day can boost bioavailability by 3-fold compared to taking it on an empty stomach.

Algae oil for vegans and vegetarians

Algae-derived supplements provide EPA and DHA in the same bioactive forms as fish oil, without marine sourcing. They're also free from common fish oil contaminants like heavy metals and dioxins.

Store fish oil cold to prevent rancidity

Oxidized (rancid) fish oil can be counterproductive, increasing rather than reducing inflammation. Store your supplements in the refrigerator or freezer and discard any that smell or taste strongly fishy.

Take omega-3s with dietary fat

EPA and DHA absorption improves significantly when taken with dietary fat. Taking your supplement with your largest meal can boost bioavailability 3-fold compared to an empty stomach.

Algae oil for vegans

Algae supplements provide EPA and DHA in the same bioactive forms as fish oil. They are free from heavy metals and dioxins common in fish oil.

Store fish oil cold

Oxidized fish oil can increase rather than reduce inflammation. Store supplements in the refrigerator or freezer and discard any that smell or taste strongly fishy.

How much omega-3 should I take per day?

For general health, aim for 2-3 grams of combined EPA and DHA daily. The American Heart Association recommends at least two servings of fatty fish per week for people without heart disease. Those with elevated triglycerides or existing cardiovascular risk may benefit from higher therapeutic doses (up to 4 g/day), but should consult their doctor first. A 2024 study found that benefits for biological aging plateau around 1.1 g/day of total omega-3 intake.

What is the omega-3 index and why does it matter?

The omega-3 index measures the percentage of EPA and DHA in your red blood cell membranes, reflecting your long-term omega-3 status over the past 2-3 months. An index of 8-12% is linked to the lowest cardiovascular risk, while values below 4% indicate high risk. A pooled analysis of 17 prospective studies found that people with the highest omega-3 blood levels had 15-18% lower risk of all-cause mortality. You can test your index with a simple at-home dried blood spot test.

Is fish oil or krill oil better for omega-3?

Both provide EPA and DHA, but they differ in form and dose. Fish oil in triglyceride form offers the highest EPA+DHA content per capsule and is well-studied in clinical trials. Krill oil contains phospholipid-bound omega-3s, which some studies suggest may have slightly better absorption gram-for-gram, but krill oil capsules typically contain much less EPA+DHA per dose. For most people, a high-quality triglyceride-form fish oil or algae oil is the most practical and cost-effective choice.

Can omega-3 fatty acids slow aging?

Growing evidence suggests yes. A 2024 study of over 20,000 adults found that higher omega-3 intake was significantly associated with slower phenotypic age acceleration. Pooled data from 17 cohort studies links the highest omega-3 blood levels to 15-18% lower all-cause mortality. Some research also suggests omega-3s may protect telomere length, a marker of cellular aging, though these findings need confirmation in larger trials. The most consistent longevity signal comes from maintaining an omega-3 index of 8% or above.

Are there side effects or risks of omega-3 supplements?

At standard doses (2-3 g/day), omega-3 supplements are generally well tolerated. Common minor side effects include fishy aftertaste, mild digestive discomfort, and loose stools. At high doses (above 3-4 g/day), omega-3s may increase the risk of atrial fibrillation in some people, particularly those already at risk. They can also have a mild blood-thinning effect, so people on anticoagulant medication should consult their doctor before supplementing.

Is fish oil or krill oil better?

Both provide EPA and DHA. Fish oil in triglyceride form offers higher EPA+DHA content per capsule and is well-studied. Krill oil contains phospholipid-bound omega-3s which may absorb slightly better, but contains less EPA+DHA per dose. For most people, high-quality triglyceride-form fish oil or algae oil is most practical.

Are there side effects of omega-3 supplements?

At standard doses (2-3 g/day), omega-3s are generally well tolerated. Common minor effects include fishy aftertaste, mild digestive discomfort, and loose stools. At high doses (above 3-4 g/day), omega-3s may increase atrial fibrillation risk in some people. Those on blood thinners should consult their doctor first.