DHA (docosahexaenoic acid)

Does DHA improve memory?

Updated 9 Nov 2026

Short answer

In healthy older adults, probably not much. A review of 10 studies with 2,327 older adults found no clear effect of DHA on memory, attention or executive function.[1] Some single trials found gains, for example with 900 mg a day for 24 weeks.[2] In mild to moderate Alzheimer's disease, 2 g a day for 18 months did not slow decline.[3]

What the reviews found

A 2020 review of 10 studies with 2,327 older adults found minimal or no effect of DHA on memory, attention, working memory and executive function.[1] The authors concluded that the evidence does not support DHA to prevent or slow age-related decline in these areas.[1]

A 2024 review of 24 studies with 9,660 adults aged 40 or older without dementia looked at omega-3 fats in general. It found a possible benefit on executive function, the skills used to plan and switch tasks. The benefit showed mostly in the first 12 months and at more than 500 mg a day.[4]

The NIH sums up the trials this way: omega-3 supplements do not change thinking in healthy older adults or in Alzheimer's disease. They may help some aspects in mild cognitive impairment, but this needs more trials.[5]

Trials of DHA alone

  • MIDAS: 485 healthy adults aged 55 or older, with memory below that of younger adults, took 900 mg a day for 24 weeks. They made fewer errors on a visual learning and memory test and did better on verbal recognition memory. Working memory and executive function did not change.[2]
  • In China, 240 adults aged 65 or older with mild cognitive impairment took 2 g a day for 12 months. IQ scores and digit span improved, and the hippocampus, a memory area of the brain, shrank less.[6]
  • In New Zealand, 176 healthy adults aged 18 to 45 with a low DHA intake took 1.16 g a day for 6 months. Their memory reaction times became faster. Episodic memory improved in women, and working memory speed in men.[7]
  • In 402 people with mild to moderate Alzheimer's disease, 2 g a day of algal DHA for 18 months did not slow decline. The ADAS-cog score worsened by 7.98 points with DHA and 8.27 points with placebo, and the brain shrank at the same rate.[3]

Why it may work

  1. DHA is a part of the membranes of brain cells.[5]
  2. Researchers think omega-3 fats may help keep nerve cells working.[5]
  3. In case-control studies, people with Alzheimer's disease had lower blood DHA than healthy people.[5]

What is still unknown

Single trials found gains, but a pooled review of DHA trials found little or none.[1][2] The effect may depend on the starting level: the young adults who improved had a low DHA intake.[7] The 2024 review found the clearest trends where blood DHA and EPA were not very low.[4]

Sources (7)

  1. Docosahexaenoic acid supplementation in age-related cognitive decline: a systematic review and meta-analysis. Balachandar R, Soundararajan S, Bagepally BS Eur J Clin Pharmacol, 2020. PMID 32060571
  2. Beneficial effects of docosahexaenoic acid on cognition in age-related cognitive decline. Yurko-Mauro K, McCarthy D, Rom D, Nelson EB, Ryan AS, Blackwell A, et al. Alzheimers Dement, 2010. PMID 20434961
  3. Docosahexaenoic acid supplementation and cognitive decline in Alzheimer disease: a randomized trial. Quinn JF, Raman R, Thomas RG, Yurko-Mauro K, Nelson EB, Van Dyck C, et al. JAMA, 2010. PMID 21045096
  4. The influence of n-3 polyunsaturated fatty acids on cognitive function in individuals without dementia: a systematic review and dose-response meta-analysis. Suh SW, Lim E, Burm SY, Lee H, Bae JB, Han JW, et al. BMC Med, 2024. PMID 38468309
  5. Omega-3 Fatty Acids: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  6. Effects of DHA Supplementation on Hippocampal Volume and Cognitive Function in Older Adults with Mild Cognitive Impairment: A 12-Month Randomized, Double-Blind, Placebo-Controlled Trial. Zhang YP, Miao R, Li Q, Wu T, Ma F J Alzheimers Dis, 2017. PMID 27716665
  7. DHA supplementation improved both memory and reaction time in healthy young adults: a randomized controlled trial. Stonehouse W, Conlon CA, Podd J, Hill SR, Minihane AM, Haskell C, et al. Am J Clin Nutr, 2013. PMID 23515006

More about dha (docosahexaenoic acid)

What is DHA?Does DHA lower inflammation?How much DHA is recommended in pregnancy?What is the difference between DHA and EPA?What is DHA used for?Can the body make its own DHA?

For education; not medical advice. Talk to a doctor before you start, stop or change a supplement.