Omega-3

Omega-3

Omega-3 fatty acids, specifically EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), are essential fats your body can't produce on its own. They're structural components of every cell membrane in your body, precursors to anti-inflammatory signalling molecules, and critical for brain, heart, and joint function. If you eat a modern Western diet, you're almost certainly not getting enough, and the downstream effects touch everything from cardiovascular risk to recovery from training to how well your brain works under stress.
The reason omega-3s matter so much practically is that most people are heavily skewed toward omega-6 fatty acids (from seed oils, processed food, and grain-fed meat), which drive pro-inflammatory pathways. EPA and DHA directly compete with omega-6-derived arachidonic acid for incorporation into cell membranes, and when your membranes have more EPA and DHA, they produce fewer inflammatory mediators (prostaglandins, thromboxanes, leukotrienes) and more anti-inflammatory ones (resolvins, protectins, maresins). The full mechanism behind how dietary fat composition drives inflammation is covered on our metabolic system page. The practical result is less systemic inflammation, better recovery, and reduced long-term disease risk, and this shows up as measurable reductions in CRP, IL-6, and TNF-α in meta-analyses of supplementation trials.
There are three omega-3s you'll encounter: ALA (alpha-linolenic acid, from flaxseed, chia, walnuts), EPA, and DHA (both from marine sources). ALA is essentially useless for what we're discussing here because conversion to EPA is extremely low (around 2-10%) and to DHA is near zero (one study found less than 0.01% conversion to DHA). If someone tells you they get their omega-3 from flaxseed oil, they are not getting EPA or DHA in any meaningful amount. You need marine-sourced omega-3s, either from fatty fish or from EPA/DHA supplements.
The most useful way to assess your omega-3 status is measuring the percentage of EPA + DHA in your red blood cell membranes, sometimes called the Omega-3 Index. Because red blood cells turn over every 3-4 months, this reflects your average intake over that period rather than what you ate yesterday (similar to how HbA1c reflects long-term blood sugar rather than a single fasting glucose reading). An EPA+DHA level of 8% or higher is associated with the lowest cardiovascular risk. Between 4-8% is intermediate. Below 4% is high risk. An analysis of NHANES 2011-2012 data found that 88.7% of US adults fell into the high cardiovascular risk category, and average values in the US and Europe sit around 5%. The Japanese population averages around 9%, which tracks with their significantly lower rates of cardiovascular disease despite higher rates of smoking and hypertension.
Cardiovascular health is where omega-3s have the deepest evidence base. EPA and DHA lower triglycerides in a dose-dependent, roughly linear fashion, with a dose-response meta-analysis of 90 RCTs confirming this relationship. At higher doses (2-4g/day), triglyceride reductions of 25-30% are consistently observed. They also reduce blood pressure modestly (3-4 mmHg systolic at higher doses), improve endothelial function, reduce platelet aggregation, and lower resting heart rate. A meta-analysis found that each additional 1g/day of EPA+DHA was associated with a 5.8% reduction in cardiovascular events and a significant reduction in fatal MI. A pooled analysis of over 183,000 participants found that those with the highest circulating EPA levels had a 17% lower risk of total stroke compared to those with the lowest levels.
Brain and mental health: DHA makes up roughly 20% of the fatty acids in the brain and is the most abundant omega-3 in neural tissue. EPA, while less concentrated in the brain, appears to be the more important fatty acid for mood, likely through its anti-inflammatory effects on neuroinflammation and its ability to increase BDNF (brain-derived neurotrophic factor) and support serotonin and dopamine signalling. A meta-analysis of 26 RCTs covering 2,160 participants found a statistically significant benefit of omega-3 supplementation on depressive symptoms, with preparations containing at least 60% EPA showing the strongest effects. Higher-dose EPA (around 1-2g/day) appears to work best for depressed individuals who also have elevated inflammatory markers. For general cognitive maintenance, adequate DHA intake throughout life helps support membrane fluidity and neuronal signalling.
Inflammation and exercise recovery: A 2026 meta-analysis of 41 studies found that omega-3 supplementation consistently reduced post-exercise IL-6, TNF-α, creatine kinase (CK), and delayed-onset muscle soreness (DOMS). The mechanism is twofold: EPA and DHA incorporate into muscle cell membranes, making them structurally more resistant to exercise-induced damage, and they dampen the inflammatory cascade that follows intense training. Practically, this means less soreness and faster recovery between sessions. The International Society of Sports Nutrition supports the use of omega-3s in athletes, noting benefits for endurance capacity, reduced DOMS, and improved cardiovascular function during exercise. The recovery benefits appear more pronounced in recreational athletes and in women, likely due to differences in baseline membrane composition and immune responsiveness.
Muscle protein synthesis: There's growing evidence that omega-3s are at least anti-catabolic and potentially mildly anabolic, particularly in contexts of anabolic resistance (aging, immobilisation, caloric deficit). One study in young women found that 5g/day of omega-3s cut muscle loss nearly in half during two weeks of leg immobilisation. In older adults, 3.36g/day for two months increased muscle protein synthesis in the presence of amino acids and insulin. The mechanism appears to involve upregulation of mTOR signalling and improved insulin sensitivity at the muscle level, not a direct hormonal effect.
For women, omega-3s are relevant well beyond reproductive health. EPA and DHA reduce prostaglandin E2 and F2α production, which are the main drivers of uterine contractions and menstrual pain. Multiple studies show omega-3 supplementation significantly reduces dysmenorrhea, in some cases outperforming ibuprofen. Omega-3s also improve ovulatory function, with one study in 259 healthy premenopausal women finding that higher omega-3 intake was associated with increased progesterone amplitude and healthier hormonal patterning across the menstrual cycle. Postmenopausal women face accelerated cardiovascular risk as protective oestrogen declines, making the triglyceride-lowering and anti-inflammatory effects of omega-3s particularly valuable. The cardiovascular, cognitive, and anti-inflammatory benefits apply equally to women as to men, and the recovery benefits from exercise may actually be more pronounced in women based on the available data. No female-specific dose adjustment is needed for general supplementation.

Dosage:

  • Dosage: 1-2g combined EPA+DHA daily is enough for the general individual, depression or menstrual pain, starting from a typical Western baseline.
    For active individuals and athletes, aim for 2-3g EPA+DHA daily for inflammatory markers and muscle damage.
  • MAKE SURE you read on the ingredients that’s it 1-4g of EPA & DHA. Many cheaper alternatives advertise something like “1000g fish oil per capsule”, out of which only 30% is actual EPA & DHA. Meaning you’d have to take 7 capsules to hit the lower end for athletes.
  • Best form: If you want to optimise for price, buy cheaper ethyl ester (EE) fish oils, just make sure you take them with food. If you have GI discomfort or want to take them on an empty stomach, go for triglyceride (TG) or re-esterified triglyceride (rTG) forms. If the label doesn't specify the form, it's almost certainly ethyl ester. If it says triglyceride, rTG, or TG, it'll be stated clearly because the manufacturer paid more for it and wants you to know.
  • EPA to DHA ratio: For general health, the standard ratio most fish oils come in (roughly 3:2 or 2:1 EPA to DHA) is fine.
  • Freshness matters. Store fish oil away from heat and light. Some fishiness is normal. The warning sign is a sharp, rancid smell or bitter, acrid taste when you open the bottle or burp, that means the oil has oxidised and you should throw it out. If you want to go further, look for brands that publish a TOTOX (total oxidation) value on their site, lower is better.
  • Best food sources (combined EPA+DHA per 100g cooked, from USDA FoodData Central):
    • Atlantic mackerel: ~2,670mg
    • Wild Atlantic salmon: ~2,260mg
    • Atlantic herring: ~2,150mg
    • Anchovies: ~2,050mg
    • Sardines (canned, drained): ~980mg
    • Rainbow trout: ~980mg
    • Oysters (Pacific): ~1,280mg
    • Mussels: ~780mg

Here's what you can expect:

Omega-3s are a slow-burn supplement. You won't feel anything immediately. Red blood cell membranes take 3-4 months to fully turn over and incorporate the new fatty acid profile, so most benefits build gradually. Reduced muscle soreness and improved recovery may be noticeable within 4-6 weeks of consistent dosing at 2g+/day. Triglyceride reductions show up on bloodwork at 4-8 weeks. Mood and cognitive improvements, where applicable, tend to emerge around 8-12 weeks. Skin quality improvements (reduced dryness, less inflammatory acne) are commonly reported at 2-3 months.

Side effects & risks:

  • GI discomfort, fishy aftertaste, and fishy burps are the most common complaints, especially with cheaper ethyl ester products. Taking with food, switching to a TG/rTG form, or freezing capsules before taking them usually resolves this
  • Atrial fibrillation (AF) is the most clinically relevant concern at higher doses. A meta-analysis of 7 large RCTs found a dose-dependent increase in AF risk, with each additional 1g/day increasing the hazard ratio by about 11%. The risk is most significant at pharmaceutical doses (3-4g/day) in people already at high cardiovascular risk, particularly older populations with existing heart disease. Interestingly, a pooled analysis of 17 observational cohorts with over 54,000 people found that higher blood levels of omega-3s were actually associated with 6-13% lower AF risk. The emerging picture is a U-shaped relationship: too little omega-3 and too much supplemental omega-3 both appear to increase AF risk, while moderate intake (roughly 250-1,500mg/day of EPA+DHA from diet and low-dose supplements) sits in the lowest risk zone. If you're dosing above 2g/day, be aware of this signal. If you have a history of AF or significant cardiac risk factors, discuss high-dose supplementation with your cardiologist
  • Bleeding risk was historically a concern but has been largely disproven at standard supplemental doses. Omega-3s do mildly reduce platelet aggregation, but clinical trials have not shown increased surgical bleeding or haemorrhagic stroke at doses up to 4g/day. If you're on anticoagulants (warfarin, heparin) or antiplatelet drugs (aspirin, clopidogrel), mention your omega-3 use to your prescriber, but this is a precaution, not a hard contraindication
  • LDL cholesterol can increase slightly at higher doses, particularly with DHA-dominant formulations. This is typically a modest increase in LDL particle size (larger, less atherogenic particles) rather than an increase in particle number, so it's generally considered benign. If you're concerned, EPA-dominant formulations have a more neutral effect on LDL
  • Contamination with heavy metals (mercury, PCBs, dioxins) is a valid concern with low-quality fish oils. Reputable brands test for and report contaminant levels. Look for third-party certifications (IFOS, USP, NSF). Molecular distillation effectively removes heavy metals, which is one advantage of concentrated supplements over whole fish in highly polluted waters
  • Prostate cancer: An observational study from the SELECT trial suggested an association between high blood omega-3 levels and prostate cancer risk. This finding has not been replicated in subsequent larger analyses, and multiple meta-analyses have found no consistent link. The current consensus is that omega-3 supplementation does not meaningfully increase prostate cancer risk
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Blood markers

Omega-3 Index (target 8-12%), the single most useful test. Measures EPA + DHA as a percentage of red blood cell membrane fatty acids, reflecting your status over the past 3-4 months. Check at baseline before starting supplementation. Recheck at 4 months to verify you've reached target. Available as an at-home finger-prick test through services like OmegaQuant, or through your doctor as part of a fatty acid panel.
Triglycerides, check at baseline and at 8-12 weeks if supplementing for lipid management. This is the clearest objective marker of omega-3 efficacy. Expect 25-30% reduction at doses of 3-4g/day.
Full lipid panel (LDL, HDL, total cholesterol), check at baseline. Monitor LDL if supplementing with DHA-dominant formulations at higher doses, as modest LDL increases can occur.
hs-CRP (high-sensitivity C-reactive protein), check at baseline if supplementing for anti-inflammatory purposes. Useful for tracking systemic inflammation reduction over 3-6 months.
For most people, an Omega-3 Index at baseline is the only test that really matters.