by Thijs Westerbeek

A cocktail of ingredients containing omega-3 fatty acid found in fish oil is being tested in patients with mild cognitive impairment as a means to slow the progression of Alzheimer's dementia down

Scientists have long known that high levels of cholesterol around mid-life greatly increase the risk of developing dementia 30 years later. Cholesterol boosts the production of so-called beta amyloid peptides, which are the main component of the amyloid plaques found in the brains of Alzheimer patient.

However, it is unclear as to whether changing the diet could prevent dementia. Or even whether the most beneficial and effective ingredients can be delivered in a pill or a small yoghurt drink. This is precisely the questions that the EU-funded LipiDiDiet study is focusing on.

The project follows on from previous efforts to identify beneficial types of fat, also called lipids, which could be of interest for treating dementia. "In an earlier project called LipiDiet— (by contrast to the current) LipiDiDiet project—hundreds of lipids were screened to find out whether they could be beneficial," says Tobias Hartmann, a professor of experimental neurology at the Saarland University in Homburg, Germany, who is also the LipiDiDiet project coordinator.

The previous project identified several so-called 'bad' lipids, which had a negative effect, and a few which had just the opposite effect. "The best one from a practical point of view, [which] had to be digestible and non-toxic in amounts high enough to be effective, was an omega-3 fatty acid, [called] DHA, more commonly known as the active ingredient of fish oil," Hartmann tells CommNet.

But there is no consensus on whether DHA has a beneficial effect on the development of Alzheimer's disease. "In my research, I haven't seen any effect," says Ondine van de Rest, a researcher at the division for human nutrition from Wageningen University and Research Centre, in the Netherlands. Her PhD thesis focused on the effect of high dose fish oil supplementation on cognitive performance in patients with mild cognitive impairment. Her research is not the only one that casts a doubt over the protective properties of fish oil. A large intervention study by US scientists came up with the same findings.

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