People who eat a diet high in oily fish might significantly reduce their risk of developing Alzheimer's disease and dementia in later life according to research by Tufts University and published in the journal Archives of Neurology.

The diets of approximately 900 older men and women were analyzed over a period of 9 years and blood samples were taken from the participants. It was found that those who had the highest levels of DHA (Docosahexaenoic acid) in their blood reduced their risk of developing dementia by around 47% and Alzheimer's by 39% as compared to those who had low levels of DHA. The study also identified that the levels of DHA in the blood can be influenced by the liver's ability to convert ALA or alpha-linolenic acid, into DHA but that the most significant influence on the amount of DHA in the blood was actually the amount of fish consumed. Those who had the lowest risk consumed 2 or more portions of oily fish a week. It is important to note that this study doesn't prove that eating fish prevents dementia, but the suggestion is that eating fish does seem to reduce the risk.

The link between Omega 3 fatty acids and the brain is well known and research continues to highlight the myriad of ways that these fatty acids impact on brain health in general. One research team from Aberdeen and Edinburgh University in Scotland looked at the Omega 3 intake of around 300 people aged 64 and tested the levels of fatty acids in their blood. They found that those who had supplemented with Omega 3 showed better cognitive processing in mental speed tests and the results were directly related to the level of Omega 3 in their blood. They suggested that Omega 3 might be able to slow down the ageing of the brain itself. If this is the case then Omega 3 fatty acids might have some therapeutic benefit on people who are already suffering from dementia.

Indeed, one study in Sweden looked at the effect that Omega 3 fatty acids had on people who already had Alzheimer's disease. They gave 89 patients a supplement containing DHA and EPA for 6 months and another 85 patients were given a placebo. There was a cross over point at 6 months where the placebo group also began to receive Omega 3. The interesting result from this study was that 32 patients who had mild symptoms of Alzheimer's disease showed less of a decline whilst taking the supplements suggesting that the fatty acids might slow down the progress of the disease in the early stages.

The fatty acid connection – what do we know?

DHA, along with Eicosapentaenoic acid or EPA are Omega 3 fatty acids found in oily fish such as Salmon, Tuna, Herring, Mackerel and Anchovies. ALA on the other hand is a plant based Omega 3 fatty acid and research has shown that the ability to convert ALA into EPA and DHA is extremely limited in humans and can be even lower than 5%. This means that the only way to get enough EPA and DHA is to eat oily fish or to supplement with fish oil.

The brain is a fatty organ that depends largely on DHA for healthy structure and development. People with Alzheimer's and dementia have been found to have low concentrations of it and the natural assumption would be that increasing the amount of DHA in the diet might have some preventative benefits. However, if there is enough EPA in the diet then the body can produce as much DHA as required so EPA is arguably the most important of the Omega 3 fatty acids. EPA is believed to be the fatty acid mostly responsible for the general functioning of the brain on a day to day basis, and as well as having anti-inflammatory properties, appears to improve the connections in the neural networks in the brain. EPA is also thought to inhibit the activity of the enzyme phospholipase A2 and over-activity of this enzyme has been linked to neurotoxicity and death of brain cells, a feature of Alzheimer's disease and other forms of dementia.

Conclusion

It is too early to say conclusively whether eating more fish or supplementing with fish oil can actually help to prevent dementia and Alzheimer's disease or whether it might slow down degeneration and ageing of the brain but the indications are that it certainly has some influence on brain health, which isn't surprising given that the brain is composed mostly of fat and relies on the omega 3 fatty acids to develop and function properly.

What is known is that fish oil does offer protection against a number of health conditions, including heart disease, circulation problems and even depression so at the very least, supplementing with concentrated fish oil is a convenient way for anyone to boost their physical and mental health in general.