Nutrition and diet

Omega-3

Also called: fish oil, EPA DHA, essential fatty acids

Omega-3 fatty acids are a family of essential polyunsaturated fats. The body cannot make them, so you must eat them. The three main forms are EPA, DHA (both in oily fish and algae) and ALA (in flax, chia, walnuts). EPA and DHA have the strongest evidence for cardiovascular and inflammatory benefits. Aim for 2 portions of oily fish per week or supplement 250 to 500 mg of combined EPA+DHA daily.

The three forms

  • EPA (eicosapentaenoic acid): main anti-inflammatory effect.
  • DHA (docosahexaenoic acid): main neurological and visual effect.
  • ALA (alpha-linolenic acid): the plant-based parent. Body converts ~5-10 percent to EPA, less to DHA.

Sources

Best (EPA + DHA)

  • Salmon (1.5 g per 100 g cooked).
  • Sardines (1.5 g per 100 g).
  • Mackerel (2 g per 100 g).
  • Anchovies (1.5 g per 100 g).
  • Herring (1.7 g per 100 g).
  • Algae oil supplements (vegan EPA+DHA, 250 to 500 mg per capsule).

ALA only, converts poorly

  • Flaxseed (22 g ALA per 100 g).
  • Chia seeds (17 g per 100 g).
  • Walnuts (9 g per 100 g).
  • Hemp seeds (10 g per 100 g).

What omega-3 actually does

  • Reduces triglycerides (well-evidenced at 2 to 4 g/day).
  • Reduces inflammatory markers in chronically inflamed states.
  • Cardiovascular benefit: modest in primary prevention, stronger in secondary prevention.
  • Brain health: associated with lower rates of cognitive decline; causality is debated.
  • Supports the gut barrier and modulates microbiome composition.
  • Pregnancy: DHA supports fetal brain and eye development.

Dose recommendations

  • General health: 2 portions oily fish/week OR 250-500 mg EPA+DHA/day.
  • High triglycerides: 2-4 g/day under medical supervision.
  • Pregnancy: 200-300 mg DHA/day.
  • Vegan: algae-based EPA+DHA supplement, same target dose.
  • Don't exceed 5 g/day without medical guidance (mild bleeding risk increase).

What to look for in supplements

  1. Combined EPA+DHA per capsule, not just 'fish oil'. A 1000 mg fish oil capsule often has only 300 mg EPA+DHA.
  2. Triglyceride or phospholipid form (better absorbed than ethyl ester).
  3. Third-party tested for heavy metals (IFOS, USP, Friend of the Sea certifications).
  4. Stored in fridge after opening.
  5. Smell, fishy or rancid is a sign of oxidation; throw out.

Common questions

Can I get enough omega-3 from flax and chia alone?
Possibly enough ALA but not enough EPA and DHA. The conversion rate is too low for most people to hit therapeutic levels. Vegans should take an algae-based supplement to get proper EPA+DHA.
Are fish oil burps dangerous?
No, just unpleasant. Caused by oil refluxing back from the stomach. Take with food, freeze the capsules, or switch to enteric-coated versions to reduce burps.
Should I worry about mercury?
Less than for unprocessed fish. Reputable supplements remove heavy metals during processing. Check for third-party purity testing on the bottle.
Will omega-3 affect my blood thinners?
At doses under 3 g/day, minimal effect. Higher doses can mildly extend bleeding time. If you are on warfarin or DOACs, check with your prescriber before starting high-dose omega-3.

Sources