1–2 g/day (e.g. flaxseed oil). Conversion to EPA/DHA is low.
A higher ALA intake is associated with lower cardiovascular risk (RR ≈ 0.86) in meta-analyses.
View the study (meta-analysis) →⏱ 3 min read
Alpha-linolenic acid, or ALA, is the essential plant-based omega-3 fatty acid: the body cannot synthesize it and must obtain it from the diet through concentrated plant sources such as flaxseeds (the richest known food source), chia seeds, walnuts, canola oil, and, in modest amounts, leafy green vegetables; unlike EPA and DHA (the long-chain omega-3s found in oily fish, algae, and krill oil), ALA has 18 carbons and is the metabolic precursor that the body can convert, with limited efficiency, into EPA and DHA through the hepatic elongase and desaturase enzymes.
The efficiency of human conversion of ALA to EPA is modest (typically 5-10 percent) and that of ALA to DHA is very low (less than 1 percent), an important biochemical limitation: people who depend exclusively on plant sources of omega-3 (strict vegetarians or vegans) can reach acceptable EPA levels with high and constant ALA intake but rarely reach optimal DHA levels without specific supplementation with algal DHA, a relevant clinical consideration especially in women of childbearing age, pregnant women, and nursing mothers, for whom DHA intake is critical for fetal and infant brain development.
Population evidence associates high dietary ALA intake with modest reductions in cardiovascular events and coronary mortality: several prospective meta-analyses have shown 10-15 percent reductions in cardiovascular mortality for each 1-gram daily increase in dietary ALA; the effects are smaller than those of marine EPA and DHA at comparable doses but clinically relevant and achievable with modest dietary changes (1-2 tablespoons daily of ground flaxseed, chia seeds, or walnuts provide significant amounts).
On lipid profile, ALA shows modest effects in reducing triglycerides and slight improvements in the HDL/LDL ratio with supplementation at 3-9 grams daily over 8-12 weeks; the effects are quantitatively smaller than those of fish oil at equivalent total omega-3 doses and depend significantly on the baseline diet and individual metabolic profile.
As a precursor of EPA, ALA has modest indirect anti-inflammatory effects documented in reductions of inflammatory markers (C-reactive protein, IL-6) with sustained intake through diet or supplementation; these effects are consistent with the general profile of omega-3s but require significantly higher intakes than direct EPA/DHA to reach comparable magnitudes.
In fertility, several small studies have correlated plasma ALA levels with favorable reproductive parameters in both men and women; specific ALA supplementation has limited data, but consistent with a favorable nutritional profile.
The most efficient and inexpensive food sources are ground flaxseed (1-2 tablespoons daily provide 1.6-3.2 g of ALA), chia seeds (1-2 tablespoons provide 2.5-5 g), walnuts (30 g provide 2.5 g), and virgin flaxseed oil (1 teaspoon provides 2.5 g); whole flaxseeds are not completely digested and should be ground just before eating to release the nutrients and associated lignans; flaxseed oil is highly prone to oxidation and should be stored refrigerated in opaque containers, ideally consumed within a few weeks.
As a supplement, the doses studied range from 1 to 9 grams daily; for general cardiovascular prevention, 1-2 g/day through diet or supplementation; for people on a strict vegetarian diet, it is advisable to combine it with specific algal DHA supplementation to ensure adequate intake for the nervous system.
Generally very well tolerated; the adverse effects described are rare and mild (digestive discomfort, flatulence with high doses of seeds); people taking anticoagulants should be cautious because of a mild antiplatelet effect at high doses; flaxseed oil oxidizes quickly, and rancid products can cause digestive problems and lose clinical efficacy; flaxseeds contain phytates and mucilages that can interfere with the absorption of some minerals and drugs, so it is advisable to space out the doses; in pregnancy and breastfeeding, dietary ALA in usual amounts is safe and beneficial, although to ensure a supply of DHA it is advisable to supplement with oily fish or algae-derived DHA.
Information, not medical advice. Scientific evidence reflects the quality of the studies.