TL;DR

  • DHA (docosahexaenoic acid) is an omega-3 that makes up a big part of the brain and retina.
  • Our bodies make very little DHA from ALA, so most people need DHA from food or supplements (algae is a vegan source). ALA is an omega-3 fatty acid from a vegetable source, like flax seeds.
  • Research links DHA with healthy brain development, better cognitive scores with aging, and support for memory and mood in several studies.

What Is DHA and Why It Matters

DHA is a major building block of the brain, cerebral cortex, and eyes. Only 1–2% of DHA can be made from ALA (the omega-3 in plants like flax and walnuts). Because that conversion is small, aim to get DHA from:

  • Fish & shellfish (salmon, sardines, trout)
  • Algae-based DHA (good for vegans and during pregnancy)

Pregnancy & lactation: DHA makes up ~90% of brain omega-3s and about a quarter of brain fat. Research highlights DHA as important for the developing fetus; breast milk is a key source. (Biochimie 2011)

DHA, Inflammation, and Brain Health

Omega-3s help calm inflammation. Some trials compare EPA vs DHA; one head-to-head study found DHA lowered inflammation more than EPA. (Am J Clin Nutr 2016)

ADHD

Analyses of many studies link lower DHA levels with ADHD in children. (Mol Psychiatry 2016; Neuropsychiatr Dis Treat 2016)

Learning, Memory, and Aging

  • Reviews show omega-3s support cognition and memory. (Adv Nutr 2013)
  • In adults 55+ with age-related cognitive decline, 900 mg/day DHA for 24 weeks improved learning and memory. (Neurobiol Aging 2012)
  • In a 12-month trial of older adults with MCI, DHA-fortified fish oil improved short-term and working memory vs placebo. (Psychopharmacology 2013)
  • A study from the Framingham cohort linked higher plasma DHA with lower risk of all-cause dementia. (Arch Neurol 2006)
  • Reviews and meta-analyses report memory benefits in older adults with mild complaints when DHA is used alone or with EPA. (PLoS One 2015; Neurobiol Aging 2012)

Why DHA Might Decline With Age

Aging brains lose phospholipids and myelin lipids, and some research finds lower DHA in several brain regions in Alzheimer’s disease, possibly tied to liver-to-brain supply. (Acta Neuropathol 1997; PLoS One 2010)

Food High in DHA (and Vegan Options)

  • Fish/seafood: salmon, sardines, herring, trout
  • Plant ALA: walnuts, flax, chia, hemp, soy foods (conversion to DHA is limited)
  • Algae-based DHA: a direct plant-based source, useful for vegans and during pregnancy/lactation

Practical Notes

  • Many consumer products provide ~200–500 mg DHA per serving; some trials used 900 mg/day. Dosing should be personalized.
  • Work with doctors trained in natural healthcare, especially if you’re pregnant, breastfeeding, or on medications.

FAQs

Can vegans get enough DHA?
Yes. Choose algae-based DHA. Plant ALA helps, but the body converts only a small amount to DHA.

Does DHA help memory?
Several studies in older adults report memory and learning benefits with DHA intake or supplementation. (See references below.)

Is DHA safe in pregnancy?
DHA is important during pregnancy and lactation.

DHA or EPA—Which is better?
Both are helpful, but one study found DHA better than EPA at reducing inflammation Needs can vary by person.

How much should I take?
There’s no one-size-fits-all dose. Many people use 200–500 mg DHA/day from food and/or supplements; some studies used 900 mg/day. Personalize with your clinician.

References

Guesnet P, Alessandri J-M. Docosahexaenoic acid (DHA) and the developing CNS. Biochimie. 2011;93(1):7–12. PubMed: https://pubmed.ncbi.nlm.nih.gov/20478353/

Allaire J, et al. Comparing EPA vs DHA on inflammation (ComparED Study). Am J Clin Nutr. 2016;104(2):280–287. PubMed: https://pubmed.ncbi.nlm.nih.gov/27281302/

Bonvicini C, et al. ADHD in adults: genetic/pharmacogenetic/biochemical meta-analysis (PUFA signal). Mol Psychiatry. 2016;21(7):872–884. PubMed: https://pubmed.ncbi.nlm.nih.gov/27217152/

Königs A, Kiliaan AJ. Critical appraisal of omega-3s in ADHD. Neuropsychiatr Dis Treat. 2016;12:1869–1882. PMC (full text): https://pmc.ncbi.nlm.nih.gov/articles/PMC4968854/

Kuratko CN, et al. DHA & learning/behavior in healthy children (review). Nutrients. 2013;5(7):2777–2810. PubMed: https://pubmed.ncbi.nlm.nih.gov/23877090/

Svennerholm L, et al. Changes in brain membrane/myelin lipids with aging. Acta Neuropathol. 1997;94(4):345–352. PubMed: https://pubmed.ncbi.nlm.nih.gov/9341935/

Schaefer EJ, et al. Plasma PC DHA & 47% lower all-cause dementia risk (Framingham). Arch Neurol. 2006;63(11):1545–1550. PubMed: https://pubmed.ncbi.nlm.nih.gov/17101822/

Cederholm T, et al. ω-3 fatty acids & prevention of cognitive decline (review). Adv Nutr. 2013;4(6):672–676. PubMed: https://pubmed.ncbi.nlm.nih.gov/24228198/ | PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC3823515/

Mazereeuw G, et al. ω-3s & cognitive performance: meta-analysis of RCTs. Neurobiol Aging. 2012;33(7):1482.e17–1482.e29. PubMed: https://pubmed.ncbi.nlm.nih.gov/22305186/

Lee LK, et al. DHA-concentrated fish oil in MCI: 12-mo RCT. Psychopharmacology (Berl). 2013;225(3):605–612. PubMed: https://pubmed.ncbi.nlm.nih.gov/22932777/

Sinn N, et al. EPA vs DHA: mood/QOL/cognition in older adults with MCI (6-mo RCT). Br J Nutr. 2012;107(11):1682–1693. PubMed: https://pubmed.ncbi.nlm.nih.gov/21929835/

Yurko-Mauro K, Alexander DD, Van Elswyk ME. DHA & adult memory: systematic review/meta-analysis. PLoS One. 2015;10(3):e0120391. PubMed: https://pubmed.ncbi.nlm.nih.gov/25786262/ | Full text: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0120391

Astarita G, et al. Deficient liver DHA biosynthesis & cognitive impairment in Alzheimer’s. PLoS One. 2010;5(9):e12538. PubMed: https://pubmed.ncbi.nlm.nih.gov/20838618/ | Full text: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0012538