DHA May Not Slow Alzheimer's

According to a recent study, supplementation with the fatty acid docosahexaenoic acid (DHA) may not slow cognitive decline in patients with Alzheimer's disease.

Fatty acids, particularly omega-3 fatty acids like DHA, are important for the growth and functional development of the brain in infants. Earlier evidence has suggested that fish oil, which contains DHA and eicosapentaenoic acid (EPA), may help prevent cognitive decline in older adults.

The study, funded by Martek Biosciences (the manufacturer of the DHA pills used in the study) and the National Institute on Aging, included 401 adults with mild-to-moderate Alzheimer's disease. The participants were randomly assigned to receive either 2 grams of DHA or placebo daily for 18 months. A total of 295 people completed the trial.

Cognitive function was evaluated using the Alzheimer's Disease Assessment Scale and Clinical Dementia Rating and was found to be similar between both groups. When the researchers reviewed MRI scans in a subset of patients, they found that DHA did not appear to affect the rate of brain atrophy.

Although no benefit was reported in this study, fish oil has been shown to have various other health benefits. For instance, fish oil is commonly taken to help prevent heart disease, and supplementation has been shown to help lower triglyceride levels and blood pressure, reduce mortality rates and abnormal heart rhythms and prevent strokes and atherosclerosis. However, high doses may have harmful effects, such as increased risk of bleeding.

For more information about omega-3 fatty acids, please visit Natural Standard's Foods, Herbs & Supplements database.

Comments

[Juneli]

Even though DHA alone may not have much effect on dementia in Alzheimer's patients, the combination of EPA and DHA has shown some promising results for AD symptoms.

[Gail]

Through my experience, I have seen that dementia presents uniquely in each patient, and sometimes patients are diagnosed simply with dementia versus Alzheimer's disease. I wonder if there is any evidence that DHA my work on non-Alzheimer’s disease patients. Perhaps that's a new direction this research could go in.

[Alex]

John makes a good point. DHA may prevent the onset instead of slowing the progress of Alzheimer's. Alternatively, there is a possibility that the study was too short and could not detect changes that would be evident with more observation.

[Marian]

Further research is definitely needed on the topic of Alzheimer's disease. Having had a close relative suffer from this disease to the point where they no longer knew who their family was, I feel it is imperative that scientists continue to look for new alternatives. This is a truly debilitating disease, not only for the patient, but also for their family. I hope to see promising new research in the near future.

[John]

It is unfortunate that DHA wasn’t shown to slow the progression of Alzheimer’s disease. However, I would be curious to see a study on the effects of DHA before patients develop Alzheimer’s disease. It may be that DHA is not effective once the disease has been established, but would be helpful in the prevention of brain atrophy.

[VG]

Fish oil has been hailed as one of the Holy Grail of supplements. However, the pathogenesis of Alzheimer's disease is still not well understood. I am not surprised that this 18-month-long trial did not show any significant results.

[MichaelC]

This study may present evidence that DHA does not have beneficial effects for treating Alzheimer’s disease, but what about its prevention? There are many forms of dementia, Alzheimer’s being one, and routine supplementation with DHA fish oils may help reduce the risk of developing dementia, especially in people at high risk. At this point, there isn’t any treatment for Alzheimer’s that has any significant benefit. I wouldn’t expect a fish oil supplement to be any different. Future research should focus on its prevention (or delay), rather than its treatment.

[becky]

We seem to be still so far away from understanding Alzheimer's that I would want to see more testing and bigger sample-sizes before writing off anything that could be potentially helpful. Without knowing if this disease is even caused by a common source, it’s difficult to rely on uniform treatments.

[Jennifer S]

There is promising research out there for Alzheimer's. Not every study is going to show positive results. I remember reading an article about sage and the potential benefits there.

I too have a history of Alzheimer's in my family, and so I'm eager to see as much research in that area as possible, but I'm glad this article points out that the funding for this study came from the manufacturer. We need to make sure we investigte the sources of our information.

[Gina]

Sara Thomas makes a good point. I’ve been trying to find the reference for the half-life of omega-3 in membranes, but no luck. If you could cite it for me, I would be very interested. I also wonder if the steady state problem could be solved by giving a loading dose. This would have to be balanced with the risk of bleeding.

[Amber]

It is unfortunate that this study did not show benefit of DHA in Alzheimer’s! However, as stated in this article, fish oil has been shown to help in many other disease states such as heart disease and blood pressure. I have heard of it helping in these conditions before, but I never really considered the harmful effects! All I had really heard before for side effects was “fishy” burps. Seeing that high doses may cause the serious effect of increased risk of bleeding, it is definitely going to motivate me to check up on some of the other harmful effects it can cause!

[Stephanie]

Alzheimer's disease runs in my family, and it's unfortunate that DHA might not slow the progression of the disease. Knowing that it is such a mysterious disease is very scary, and it is less comforting when one of the few things known for this may not even be working. Hopefully, this will encourage more research to find medicines that can help with this disease.

[Sara Thomas]

When will scientists start doing their homework? The half-life of omega-3 in membranes (RBCs) is 180 days (6 months). Any doctor or pharmacist should know the basic rule of thumb that you need to allow 4 to 5 half-lives of a substance to reach a steady state (2.5 years in this case). It's so irritating to see bad science used to "disprove" the benefits of worthwhile supplements.

That we see any quick benefit before was due to the widespread deficiency of omega-3 in the population, but as time goes by and products get fortified and people become more aware and start supplementing or changing their diet, each additional study on omega-3 is going to find decreasing difference between placebo and omega-3. The same thing will happen with vit D, I'm sure.

Please, please, please, do your homework, do good science and always, always measure initial nutrient status. As I like to say, a supplement can "float can your boat" if you're low, but it can't "give you wings" if you're already on the level.