The omega-3 index (percentage of EPA + DHA in red blood cell membranes) responds directly to dietary intake of long-chain omega-3s. Not all omega-3 sources are equal — some are much more efficient than others at moving the index.
Highest-yield sources (contain EPA + DHA directly):
- Salmon — 1.5-2.5g EPA+DHA per 3.5 oz serving (wild is roughly similar to farmed for omega-3 content)
- Sardines — 1-2g per 3.5 oz; also high in vitamin D and calcium
- Mackerel — 1-1.5g per 3.5 oz (avoid king mackerel — high mercury)
- Herring — 1-2g per 3.5 oz
- Anchovies — 1-1.5g per 3.5 oz; sustainable, low mercury
- Oysters — 0.5-1g per serving; also high in zinc
Practical target for raising the index: fatty fish 2-3x per week. Alternative: 2-3g combined EPA+DHA daily from supplement (fish oil, krill oil, or algae oil for vegetarians).
Plant sources (ALA — requires conversion to EPA+DHA):
- Walnuts — 2.5g ALA per oz
- Flaxseed (ground) — 1.6g ALA per tablespoon
- Chia seeds — 5g ALA per oz
- Hemp seeds — 1g ALA per tablespoon
The catch: ALA conversion to EPA is roughly 5-10% and to DHA is roughly 0.5-2%. Plant sources contribute meaningfully to overall omega-3 status but shift the omega-3 index much less efficiently than fatty fish. For vegetarians, algae oil (which contains EPA and DHA directly) is far more effective than seed oils.
Timeframe: Index responds over 3-4 months. Retest at 12+ weeks after starting.