Of the 1,053 adults questioned about their eating habits and efforts to maintain brain health in telephone interviews held between September 23 and 25 2005, 83 percent said they were taking some kind of measure to promote brain health, such as physical or mental exercise.
But despite 22 percent of all respondents and 32 percent of those aged over 35 saying that memory loss is their greatest health fear, only 40 percent said that they eat foods that they believe will boost mental function.
Nonetheless, it seemed that a large proportion of respondents were somehow aware that eating fish may be beneficial for the brain: 64 percent said they need to eat more than the current average of one portion per week.
But when the researchers delved deeper into the reasons why people thought that, 52 percent said they were not familiar with the health benefits of DHA (docosahexaenoic acid), the essential fatty acid of which fish is the best dietary source.
Amongst those not eating fish, a dislike of the taste and fear of contaminants such as mercury were cited. Martek bases its marketing of its microalgae-derived omega-3 oils around the fact that they are not derived from fish, but can be added to other food products to boost DHA levels in the diet.
The National Institutes of Health recommends that healthy adults consume 220 mg of DHA a day - more than is contained in four cans of light tuna a week.
Recent scientific evidence in favor of the role of fish in promoting mental health includes a study published this month in the online edition of the Archives of Neurology (vol 62, 1-5).
The trial on elderly men and women living in Chicago found that those who reported eating fish at least once a week had a slower decline in mental function than peers who did not eat fish as often - about 10 per cent less per year.
For those eating two or more fish meals a week the rate of cognitive decline was 13 per cent slower than non-fish eaters, a rate the researchers said was equivalent to being three or four years younger in age.
However although earlier studies have put the effect down to omega-3, in this latest trial the link was said to be "weak at best". The researchers speculated that this may indicate that dietary omega-3 fatty acids may have little impact on milder forms of cognitive decline.
Recent studies have suggested a link between consumption of B-vitamins, in particular folic acid, and a reduced rate of memory decline in the elderly.