Omega-3 RDA Table
| Life stage | ALA AI (g/day) |
|---|---|
| Infant 0–12 mo | 0.5 (AI) |
| 1–3 years | 0.7 |
| 4–8 years | 0.9 |
| 9–13 years | 1.2 (M) / 1.0 (F) |
| 14–18 years | 1.6 (M) / 1.1 (F) |
| 19+ years | 1.6 (M) / 1.1 (F) |
| Pregnancy | 1.4 |
| Lactation | 1.3 |
| DHA + EPA | no separate requirement; no UL at any dose |
| Food | Portion | g | lane |
|---|---|---|---|
| Flaxseed oil | 1 tbsp | 7.26 | ALA (660% DV) |
| Chia seeds | 1 oz | 5.06 | ALA (460% DV) |
| Walnuts, English | 1 oz | 2.57 | ALA (234% DV) |
| Canola oil | 1 tbsp | 1.28 | ALA (116% DV) |
| Herring, Atlantic | 3 oz | 1.05 | DHA+EPA (0.94+0.11) |
| Salmon, Atlantic, farmed | 3 oz | 0.91 | DHA+EPA (0.59+0.32) |
| Tuna, canned white | 3 oz | 0.90 | DHA+EPA (0.73+0.17) |
| Halibut | 3 oz | 0.49 | DHA+EPA (0.32+0.17) |
| Egg, large | 1 | 0.03 | DHA |
Omega-3 has a two-lane supply chain and most advice blurs it. Lane one is ALA from plants - flaxseed, chia, walnuts, canola - where the Adequate Intake is 1.6 g a day for men and 1.1 g for women. Lane two is DHA and EPA from seafood, which have no separate official requirement at all: the body is expected to make what it needs from ALA, at conversion rates of only about 8% to EPA and 0.5-5% to DHA in healthy adults. A tablespoon of flaxseed oil hits 660% of the ALA target and delivers exactly zero pre-formed DHA.
That bottleneck is the honest core of the fish-versus-flax debate. A vegetarian running 0.5% conversion on a 1.1 g ALA intake synthesizes roughly 5 mg of DHA a day - a rounding error against what a salmon dinner supplies directly. The upper end of the conversion range belongs to young women, whose estrogen appears to up-regulate the pathway, and to people whose diets are not drowning in omega-6 oil competing for the same enzymes.
The requirement table is deliberately calm about all of this: no UL has been set at any dose - excess simply adds calories - and no DHA/EPA row appears, because official nutrition has declined to number that lane. What the table does nail down is the plant-side floor that nobody in an ordinary diet misses, and the fish values that make the direct-delivery route vivid. Seafood supplies DHA and EPA pre-formed; everything else is a conversion bet.
How to use
- Find your ALA row: 1.6 g for men from 14 and 1.1 g for women - the values hold through pregnancy (1.4 g) and lactation (1.3 g) with small adjustments; infants carry a 0.5 g AI; children scale 0.7 g (1-3) to 0.9 g (4-8) and 1.0-1.2 g through the teen years.
- Read the food table by lane: the top rows are ALA bombs - flaxseed oil 7.26 g per tablespoon, chia 5.06 g an ounce, walnuts 2.57 g, canola oil 1.28 g - while the fish rows list DHA+EPA directly (herring about 1.05 g, farmed Atlantic salmon about 0.91 g per 3 oz). A tablespoon of flaxseed oil clears the adult ALA target six times over.
- Count the lanes separately: plant ALA never substitutes for pre-formed DHA in an infant's developing retina or in any dose-response study of fish intake - so the working pattern is an ALA baseline every day from common oils and nuts, plus direct DHA+EPA a few times a week from low-mercury fish, rather than assuming one giant flaxseed dose covers both.
Frequently asked questions
How much omega-3 do I need per day?
The official AI is 1.6 g of ALA daily for men and 1.1 g for women from adolescence onward (1.4 g in pregnancy, 1.3 g while breastfeeding, 0.5 g in infancy). There is no formal DHA or EPA requirement and no UL at any dose. The Daily Value printed on labels is 1.1 g - so a tablespoon of flaxseed oil at 7.26 g ALA reads as 660% DV, a label artifact of the plant-side floor, not a megadose.
What foods are highest in omega-3?
By ALA: flaxseed oil tops the list at 7.26 g per tablespoon, then chia seeds 5.06 g per ounce, English walnuts 2.57 g, and canola oil 1.28 g. By pre-formed DHA+EPA per 3 oz serving: Atlantic herring about 1.05 g, farmed Atlantic salmon about 0.91 g, canned white (albacore) tuna about 0.90 g, halibut about 0.49 g; a large egg adds a token 0.03 g DHA. Fortified foods and vegetarian 'DHA strips' exist but deliver micrograms, not meals.
Does the body convert ALA to DHA and EPA?
Yes, poorly: controlled isotope studies put conversion at roughly 8% of ALA to EPA and 0.5-5% to DHA in healthy adults. Young women convert more efficiently (estrogen up-regulates the desaturase pathway), and a very high omega-6 intake competes for the same enzymes and pushes the numbers down. The practical read: flax and chia reliably cover the ALA floor, but they are not a functional substitute for fish or algae when pre-formed DHA is the point.
Do I need fish oil if I eat flaxseed and walnuts?
They solve different problems. The ALA target is trivially easy to hit with plants - most diets clear it without trying. The unresolved part is DHA+EPA, which plants supply only through the 0.5-5% conversion bottleneck; fatty fish delivers it directly, roughly 0.5-1 g per serving. No UL exists for any of it, so the risk asymmetry is small - but the honest framing is that flax covers the requirement, fish covers what the requirement table leaves unnumbered.
Is too much omega-3 harmful?
No upper limit has been set, because no adverse effect has been established at ordinary dietary doses - surplus omega-3 fat is simply metabolized like any other fat, adding about 40 calories per teaspoon of oil. The practical complaints at supplement doses are mundane (fishy aftertaste, loose stools), which is why the food-first pattern - oils, seeds, nuts for ALA; low-mercury fish a few times a week for DHA+EPA - needs no ceiling conversation at all.