DHA is one of the two key omega 3 fatty acids in fish and fish oil—the other being EPA—and it’s the one more clearly essential for optimal brain function.
The Alzheimer's Disease Cooperative Study (ADCS) trial lasted 18 months. It was conducted in people with mild to moderate Alzheimer's and was supported by the National Institute on Aging.
In this trial, DHA showed no effect among Alzheimer’s patients with a particular Alzheimer's-promoting gene, but it yielded minor benefits among the remaining Alzheimer’s patients.
The second trial was performed by scientists at Martek Biosciences Corporation (Martek). It lasted six months, and tested DHA supplements in healthy people to see its effect on age related cognitive decline (ARCD). After six months, omega-3 DHA supplements appeared to improve brain performance in people with mild memory loss.
Martek makes algae-derived DHA, but there is no difference between that DHA and the DHA in fish oil, which accumulates up the ocean food chain, starting with zooplankton that eat algae and ending with top-predator fish like tuna.
Both sets of findings were presented at the 2009 International Conference on Alzheimer's Disease (ICAD 2009) in Vienna.
Here’s a quick summary:
Memory improvements seen in healthy adults with mild memory problems
In an investigation dubbed the "Memory Improvement with DHA Study” (MIDAS), researchers at Martek Biosciences Corporation examined the effects of omega-3 DHA as a possible aid in preventing or ameliorating early stages of the mild form of memory loss called age-related cognitive decline (ARCD).
Scientists led by Martek’s Karin Yurko-Mauro, Ph.D., conducted a randomized, double-blind, placebo-controlled, multi-center, six month study to determine the effects of 900 mg per day of algal DHA on improving cognitive functions in 485 healthy older people (average age 70) with mild memory complaint (Yurko-Mauro K et al. 2009).
The primary measure of success was a positive change in a "visuo-spatial episodic memory” test CANTAB Paired Associate Learning (PAL).
After six months, the researchers found that the study participants taking DHA supplements made significantly fewer errors on the PAL compared to when they started the study.
Blood DHA levels doubled over the course of the study in the group taking the DHA supplements, and people’s improvements on PAL scores corresponded to rises in DHA levels.
They also observed a significant decrease in heart rate in those taking DHA that was closely linked with DHA blood levels after six months.
Blood pressure and body weight remained unchanged between groups, and blood levels of Alzheimer's related proteins (Abeta 1-40, 1-42 and hs-CRP) were not significantly different.
The researchers observed no serious treatment-related adverse effects, and the adverse effects profile for DHA was the same as for the placebo.
As Dr. Yurko-Mauro said in a Martek press release, "In our study, healthy people with memory complaints who took algal DHA capsules for six months had almost double the reduction in errors on a test that measures learning and memory performance versus those who took a placebo. The benefit is roughly equivalent to having the learning and memory skills of someone three years younger.”
Their brains performed as though they were three years younger? Not the fountain of youth, but we’ll take it!
And given what is known about the positive effects of omega-3s on brain chemistry and structure, we really need a 10-year-long controlled clinical trial to see if optimal omega-3 intake can affect the risk or severity of all forms of memory and brain function decline.
Alzheimer’s trial shows mixed results
Researchers from the Alzheimer's Disease Cooperative Study (ADCS) conducted a double blind, randomized, placebo-controlled clinical trial comparing DHA and placebo in 402 people (average age 76) diagnosed with mild to moderate Alzheimer's at 51 sites in the U.S. (Quinn JF et al. 2009).
At the beginning of the trial, all participants had a dietary DHA intake of less than 200 mg per day, compared with the widely recommended 500 mg per day minimum of total omega-3s (DHA + EPA).
Participants were given either two grams of DHA per day or placebo capsules, for 18 months.
The participants who were already taking FDA-approved Alzheimer's drugs could continue taking them during the trial.
Success was measured primarily by the rate of change on two measures used by the FDA when assessing new Alzheimer's drugs: the "Alzheimer's disease assessment scale-cognitive” test (ADAS-cog) and the "Clinical Dementia Scale-sum of the boxes” test (CDR-SOB).
Treatment with DHA appeared to increase brain DHA levels, but did not slow the rate of decline on tests of mental function (ADAS-cog), global dementia severity status (CDR-SOB), activities of daily living (ADL), or behavioral symptoms (NPI) in the study population as a whole.
There was no different treatment effect between patients diagnosed with the mild and moderate stages of Alzheimer’s.
However, the study detected slower declines among participants who did not carry the "e4” version of the "ApoE” gene, which increases the risk of developing Alzheimer’s.
Those without the ApoE-e4 gene who received DHA had a slower rate of decline on the primary test of mental function (the ADAS-cog), and a trend in the same positive direction was seen on another test of mental function called the Mini-mental state examination.
In contrast, people who had the ApoE-e4 gene showed no benefits from taking DHA supplements.
- Quinn JF et al. A clinical trial of docosahexanoic acid (DHA) for the treatment of Alzheimer's disease [Presentation #O1-04-02; July 12, 2009]. In: Alzheimer's Association 2009 International Conference on Alzheimer's Disease (ICAD 2009), Vienna Austria.
- Yurko-Mauro K et al. Results of the MIDAS Trial: Effects of Docosahexaenoic Acid on Physiological and Safety Parameters in Age-Related Cognitive Decline [Presentation #O1-04-01; July 12, 2009]. Alzheimer's