Eating a meal of seafood or other foods containing omega-3 fatty acids at least once a week may protect against age-related memory loss and thinking problems in older people, a new study has claimed.
Age-related memory loss and thinking problems of participants in the study who reported eating seafood less than once a week declined more rapidly compared to those who ate at least one seafood meal per week, researchers said.
"This study helps show that while cognitive abilities naturally decline as part of the normal ageing process, there is something that we can do to mitigate this process," said Martha Clare Morris from Rush University Medical Centre in the US.
Researchers followed 915 people with a mean age of 81.4 years for an average of five years. At study enrolment, none had signs of dementia.
During the course of the study, each person received annual, standardised testing for cognitive ability in five areas - episodic memory, working memory, semantic memory, visuospatial ability and perceptual speed.
Participants also completed annual food frequency questionnaires, allowing researchers to compare participants' reported seafood intake with changes in their cognitive abilities as measured by the tests.
The questionnaires included four types of seafood - tuna sandwiches; fish sticks, fish cakes and fish sandwiches; fresh fish as a main dish; and shrimp, lobster and crab.
The participants were divided into two groups - those who ate at least one of those seafood meals per week and those who ate less than one of those seafood meals per week.
Participants in the higher seafood consumption group ate an average of two seafood meals per week. Those in the lower group ate an average of 0.5 meals per week, researchers said.
Seafood is the direct nutrient source of a type of omega-3 fatty acid (docosahexaenoic acid) that is the main structural component of the brain, they said.
Researchers found associations between seafood consumption and two of the areas of cognitive ability that they tested. People who ate more seafood had reduced rates of decline in the semantic memory, which is memory of verbal information, researchers said.
They also had slower rates of decline in a test of perceptual speed, or the ability to quickly compare letters, objects and patterns, they said.
The protective association of seafood was even stronger among individuals with a common genotype (APOE-e4) that increases the risk of developing Alzheimer's disease, researchers said.
The APOE is a gene involved in cholesterol transport to neurons. About 20 per cent of the population carries the APOE-e4 gene, although not everyone who has the gene will develop Alzheimer's disease, they said.
The findings were published in the journal Neurology.
