A diet that is high in fish oil could possibly be good for the brain. Carla Dullemeijer of the Division of Human Nutrition of Wageningen University reached this conclusion in her doctoral dissertation. She discovered a clear correlation between fish fatty acids in the blood and a reduced hearing loss among the elderly: ‘Fish oil can possibly slow the decline of certain brain functions and even slow hearing loss.’
Years ago, the comic strip hero Obelix was advised to eat more fish because this was supposed to be good for the brain. Now, the scientific support of the positive effect of fish on the brain has come a step closer. Long chain omega-3 fatty acids, which occur frequently in fatty fish, appear to have a positive effect on the brain.
Dullemeijer discovered that elderly subjects with relatively low blood levels of long chain omega-3 fatty acids experienced a more rapid decline in their performance on cognitive tests than those with higher blood levels of these fish fatty acids. Previous research had shown that young pigs use the omega-3 fatty acid docosahexaenoic acid (DHA) in their brain structure during the first months of life, when the brain is developing. ‘Because DHA is apparently important to brain development, it could also play a role in brain aging’, explains the PhD student. ‘Therefore, we focused our research on several brain functions of elderly subjects in relation to the fatty acid profile in their blood.’
The positive effect of fish oil on blood vessels and circulation has been known for some time, and therefore Dullemeijer tested the hypothesis that it could be the cause of the better brain function of elderly who have a diet that is high in fish. For this purpose, she looked at the inner ear, a part of the head with very good blood circulation. In the inner ear, the cochlea converts incoming sound into an electrical signal that is transmitted to the brain via the auditory nerve. That hypothesis was that reduced circulation in the brain could affect the cochlea and lead to hearing loss. ‘Elderly who have relatively high blood levels of long-chain omega-3 fatty acids indeed turned out to have less hearing loss than elderly with relatively low blood levels of these fatty acids’, relates Dullemeijer. ‘However, this difference in hearing loss applies only to the low tones.’ The anatomy of the middle in her ear can provide a beautiful explanation of this phenomenon. ‘The cochlea is fed by a single blood vessel, which follows the windings of the broader portion to the top’, explains Dullemeijer. With reduced circulation, you would expect reduced blood supply especially at the top, which causes the damage. ‘Because low sound frequencies are processed at this location, this could indicate reduced microcirculation, which in turn could explain a possible beneficial role of the omega-3 fatty acids, especially regarding the low tones.’
Carla Dullemeijer defended her doctoral thesis on 15 May; her doctoral supervisors were Prof. Frans Kok, professor of Nutrition and Health, and Prof. Robert-Jan Brummer, Professor of Gastroenterology and Clinical Nutrition at Örebro University in Sweden and Professor of Medical Nutritional Studies and Clinical Dietetics at Maastricht University. / Hans Wolkers
The above article was written by the editorial staff of Resource, the weekly newspaper for Wageningen University and Research Centre. For more information, contact the press and science information officer of Wageningen UR, e-mail: pers.communicatie@wur.nl or the editorial staff of Resource, e-mail: resource@wur.nl. See the archived articles at www.resource-online.nl