Omega-3 Fatty Acids and Slowing the Progression of Alzheimer’s Disease: Fact or fishy?

Dr. Leah Hassall, ND

One of the concerns of aging is cognitive decline and dementia. Omega-3 fatty acids (i.e. plant and fish oils) are readily available and are frequently used for many inflammatory conditions. I am often asked if fish oils can help slow the progression of Alzheimer’s disease or even prevent it. In this article, I hope to shed some light on the available evidence.

There are three types of omega-3 fatty acids that are known to be involved in human health: ALA (found in plant oils like nuts and seeds, flaxseed, soybean and canola oils), EPA and DHA (found in marine oils like fish, algae and plankton). Omega-3 fatty acids are an important part of the membrane that surrounds cells. They also have many functions in blood vessels, lungs, the immune system and hormone production. DHA levels are especially high in the brain and retina (in the eyes).

The Cochrane Group, an independent group that summarizes good quality evidence to inform healthcare practitioners, summarized three randomized control trials that investigated 632 people with Alzheimer’s disease with mild to moderate severity. In all 3 trials, people either took placebo (pretend treatment) or an omega-3 PUFA (mixed DHA and EPA) supplement (1.8 grams – 2.3 grams/day depending on the study). When the results of the trials were combined, they found that there was no effect on cognition (learning and understanding), everyday functioning, quality of life or mental health after 6 months of supplementation. There was one study that found that the omega-3 supplementation improved cognitively complex daily activities (i.e. shopping) when taken for a longer period of time. None of the studies reported significant harmful effects of omega-3 supplementation on health.

Other studies have looked more closely at just supplementation with DHA and cognitive decline. High dose DHA appears to be somewhat beneficial in reducing the rate of cognitive decline in the elderly, but otherwise healthy person (900 mg/day for 24 weeks). However, when DHA supplementation alone was studied in people with mild to moderate Alzheimer’s disease, it did not slow the rate of cognitive and functional decline. The rate of atrophy was also not affected (2 g DHA from algae/day for 18 months).

Omega 3 Fatty Acid for the Prevention of Dementia

It is generally accepted that diets high in omega-3 fatty acids may not only protect people from cognitive decline and dementia, but also heart disease and stroke. Unfortunately, there have not been studies done on the direct effect of omega-3 fatty acids and the incidence of dementia. Meaning that we cannot say for sure that taking omega-3 fatty acids long-term (i.e. many years) will prevent the onset of Alzheimer’s disease and other forms of dementia.

The Bottom Line

Omega-3 fatty acid supplementation (like fish oil) has been studied for the treatment of multiple conditions (including depression, rheumatoid arthritis, ADHD, asthma and prevention of heart disease). There have been studies showing positive effects for many of those conditions, but to date, the evidence for supplementation for the treatment of Alzheimer’s disease is low. As naturopathic physicians, we know that it is not just one thing that prevents disease, it is a combination of healthy habits. This includes a diet high in antioxidants (fresh fruits and vegetables), omega-3 fatty acids (cold water and oily fish, cold-pressed oils and plant sterols), low refined sugar, exercise, good sleep and mood, balanced hormones and keeping cognitively active (socializing with friends and family, learning new skills/language, reading, music and dance) that prevent or slow the progression on dementia. If you are considering supplementing with a fish oil, it is important to find a company that offers a purity check where you can enter the batch number of your fish oil to view the purity report. This will ensure that you know the date of production (i.e. not rancid/old), that it has the right amount of EPA and DHA and that it does not contain unacceptable levels of heavy metals and other toxins (BPA, phthalates, PCPs).



Burckhardt, M., Herke, M., Wustmann, T., Watzke, S., Langer, G., Fink, A. (2016). Omega-3 fatty acids for the treatment of dementia. Cochrane Database of Systematic Reviews, Issue 4.


Chew, E.Y., Clemons, T.E., Agrón, E., Launer, L.J., Grodstein, F., Bernstein, P.S. (2015). Age-Related Eye Disease Study 2 (AREDS2) Research Group. Effect of Omega-3 Fatty Acids, Lutein/Zeaxanthin, or Other Nutrient Supplementation on Cognitive Function: The AREDS2 Randomized Clinical Trial. JAMA 314(8):791-801. Office of Dietary Supplements – Omega-3 Fatty Acids. (2018, November 21). Retrieved February 14, 2019, from Sydenham, E., Dangour, A.D., Lim, W.S. (2012). Omega 3 fatty acid for the prevention of cognitive decline and dementia. Cochrane Database of Systematic Reviews, Issue 6.


Yurko-Mauro, K., McCarthy, D., Rom, D., Nelson, E.B., Ryan, A.S., Blackwell, A., Salem, N. Jr., Stedman, M. (2010). MIDAS Investigators. Beneficial effects of docosahexaenoic acid on cognition in age-related cognitive decline. Alzheimer’s Dement. 6(6):456-64.