In a paper published in the inaugural issue of Aging Health, Ross Andel and Tiffany Hughes of the University of Florida's School of Aging Studies noticed strong evidence for a connection between low levels of folic acid and vitamin B12, and high and low levels of high density lipoproteins.
This week, Harvard Medical School warned in its Health Letter that vitamin B12 deficiency is the most common nutritional deficiency in the Western world.
In the diet, B12 is present in meat, poultry, fish, eggs and dairy products - which means that vegetarians are particularly vulnerable.
Adults over 50 are also more likely to be lacking than most, as a third of people in this age-group suffer from atrophic gastritis whereby the stomach lining thins and the amount of B12 absorbed by the small intestine is reduced.
In both of these groups, B12 levels can be boosted by supplementation.
On certain other dietary factors, the researchers' observations may suggest that steering a middle course is the best strategy: high and low calorific intake were seen to be risk factors, as were high and low blood sugar, antioxidant levels (in particular vitamin E), and alcohol consumption.
Andel said that finding ways to stave off cognitive decline is an important area of research.
"Cognitive decline and dementia are among the most feared age-related problems. Because of the aging baby boom population, prevention issues have taken the spotlight."
Prevention could have a profound impact on the future of nursing homes, health care costs and the burden placed on caregivers.
Beyond nutrition, the review also looked at early life factors, such as fewer siblings, higher level of education, and higher socioeconomic status of parents, all of which were associated with a lower risk and seemed to point towards the establishment of a "cognitive reserve".
In later life, intellectual stimulation at work and at leisure was seen to reduce risk, while lifestyle and life-course like poor fitness, vascular disease, diabetes and stress increased it.
The authors concluded that the way is open for further research on the subject, which should help pinpoint specific strategies to maintain cognitive abilities.