Researchers from Case Western Reserve University in the US reported on their findings at the annual meeting of the American Neurological Association, running the last week of September.
In their study, they gathered food intake data from 117 people with Alzheimer's disease and 356 people without dementia.
People that had a diet rich in linoleic acids (at least 6.6 per cent of their daily calories) had almost half the risk of developing the condition than those eating little of such fats.
But for people known to have the ApoE e4 gene, which significantly raises the risk of Alzheimer's disease, a fatty diet appeared to boost their risk even more, said Sara M. Debanne, professor of epidemiology and biostatistics at Case Western Reserve University.
Debanne's team was unable to explain this finding but it demonstrates how important the link between genes and diet.
About a quarter of the population inherit one copy of the ApoE4 gene, increasing their risk of developing Alzheimer's disease by up to four times. Two per cent of the population get a double dose of the ApoE4 gene, one from each parent, raising the risk by 16 times although it is still not inevitable that the disease will develop.