Science - December 16, 2009

Fish fatty acids don't make you cleverer or happier

A diet rich in fish fatty acids has no effect on cognitive functions such as memory and concentration in the elderly. Nor does it affect their level of wellbeing. This is the conclusion drawn by Ondine van de Rest in the thesis for which she will get her PhD from the Department of Human Nutrition on 18 December.

The human brain
'Oily fish has been in the limelight for a while because a number of studies based on animals suggested that fish fatty acids are tops', says Van de Rest. Besides their positive effect on the cardiovascular system, these unsaturated fatty acids were also thought to be good for the brain. However, the effect of fish oils on specific brain functions and on wellbeing had never been tested in human experiments.

So it was with great expectations that Rest set out to research the benefits of a diet rich in fish fatty acids for a group of over three hundred over-65s. For thirteen weeks, one group received fish oil capsules with the equivalent of ten portions of fish per week, a second group took the equivalent of two portions of fish, and a third group got placebos. The test subjects were tested before and after the experimental period on their wellbeing and on cognitive functions such as 'attention', 'speed' and 'memory'. 'Unfortunately, we found absolutely no difference between the groups', says the mildly disappointed PhD candidate. 'Of course this is only a relatively short-term study, but there wasn't even a trend to be detected that could suggest that fish oil has a positive effect on brain functions.'

Health claims
Van de Rest's research places a big question mark over the claims of supplement manufacturers (see article on supplements).  The claim is made on bottles of fish oil capsules that the product improves memory and concentration. 'That is very questionable. Up to now, neither the literature not our own research provides sufficient basis for this health claim', says Van de Rest. 'The evidence that fish oils have a positive effect on the cardiovascular system is much stronger.' That is good news for fish lovers: even if it won't make you any cleverer, oily fish is still good for you.