A recent study from Oregon Health and Sciences University casts doubt on whether fish oil may help patients with Alzheimer’s Disease. For 18 months, patients with the illness where given either 2 grams a day of docosahexaenoic acid (DHA, an omega-3 fatty acid found in fish oil) or a placebo. Those who received the DHA did no better in cognitive tests than the placebo group, and MRI scans showed no improvement in brain atrophy either. These results were recently published in the Journal of the American Medical Association. While Joseph Quinn, leader of the study, admits in the paper to JAMA that there are limitations to the conclusions that can be drawn from his experiment, his work seriously challenges those who hoped that fish oil could have a restorative effect on those with Alzheimer’s. Sadly, it looks like fish oil has failed us…again.
Fish oil, which contains omega-3 fatty acids which seem key to mental and physical health, has long been thought to have some potential to combat degenerative mental diseases. Alzheimer’s Disease forms amyloid plaque on the brain, and tests with transgenic mice who have Alzheimer’s have shown that fatty acid supplements can have a preventative and even curative effect for those with plaque buildup. At the same time we know that most humans don’t get as much fatty acid as used in experimental conditions, so it seemed natural to believe that relatively strong doses of DHA could have as yet unseen positive effects on people with the disease. This recent failure with human models is disappointing as it suggests that humans don’t seem to be affected in the same way as the mice, and that there may be little benefit (to Alzheimer’s patients) of upping their DHA intake.
But wait, you say, is this experiment really so cut and dry? Didn’t Quinn admit that his test isn’t a death knell for fish oil, just a mark against it? Good points, my vocal and imaginary reader. Indeed, the study at Oregon HSU had its limitations. First was its brevity – 18 months is a decent length of time for a nutritional/drug study but perhaps DHA takes longer to reduce plaque buildup on the brain and improve cognition scores. Likewise, this test can only really deny that DHA may work as a curative agent for Alzheimer’s. Prevention is still up in the air. The average age for the patients was 76 – maybe we need to focus on younger people who are at high risk for Alzheimer’s. Perhaps DHA is only going to delay the onset and severity of the disease.
Critics have also pointed to the exclusion of eicosapentaenoic acid (EPA) from the study. EPA is the other important omega-3 typically found in fish oil besides DHA. Can we really call this study a fail for fish oil if only half the fishy components were used? Quinn says yes. In the opening remarks of the JAMA paper, EPA is discussed and dismissed. In repeated tests using fish oil, it was found that only DHA, not EPA, makes it to the brain in appreciable quantities. It seems reasonable then to focus on DHA for fish oil studies looking to explore brain health and disease.
In the end this recent work at Oregon should only encourage us to explore the possibilities with fish oil further. The study only really addressed a single question: will patients in their mid to late 70s with Alzheimer’s see fairly quick benefits from taking fish oil supplements? The answer there seems to be a regrettable no. However, there are still many other related questions to answer if we want to understand how DHA can affect amyloid plaque buildup and Alzheimer’s Disease.
We also need to learn more about fish oil and health supplements in general. Quinn and his team studied 400 patients from 51 different testing sites across the US (only 295 completed the 18 months). The upcoming VITAL study we’ve discussed in the past will look at 20,000 patients taking fish oil and vitamin D and will have $20 million in funding. Chances are that VITAL will be able to tell us much more about the general effects of these supplements (though it won’t address Alzheimer’s). DHA may have failed this round, but there are many more to go. Good luck fish oil fans…it looks like you’re going to need it.
[image credit: Aaron Saenz/Singularity Hub]
[source: Quinn et al 2010 JAMA]