For the study, researchers examined the diets of 8,085 men and women over the age of 65 who did not have dementia at the beginning of the study. Over four years of follow-up, 183 of the participants developed Alzheimer's disease and 98 developed another type of dementia.
The study found people who regularly consumed omega-3 rich oils, such as canola oil, flaxseed oil and walnut oil, reduced their risk of dementia by 60 percent compared to people who did not regularly consume such oils. People who ate fruits and vegetables daily also reduced their risk of dementia by 30 percent compared to those who didn't regularly eat fruits and vegetables.
The study also found people who ate fish at least once a week had a 35-percent lower risk of Alzheimer's disease and 40-percent lower risk of dementia, but only if they did not carry the gene that increases the risk of Alzheimer's, called apolipoprotein E4, or ApoE4.
"Given that most people do not carry the ApoE4 gene, these results could have considerable implications in terms of public health," said study author Pascale Barberger-Gateau, PhD, of INSERM, the French National Institute for Health and Medical Research, in Bordeaux, France. "However, more research is needed to identify the optimal quantity and combination of nutrients which could be protective before implementing nutritional recommendations."
In addition, the study found people who did not carry the ApoE4 gene and consumed an unbalanced diet characterized by regular use of omega-6 rich oils, but not omega-3 rich oils or fish were twice as likely to develop dementia compared to those who didn't eat omega-6 rich oils, which include sunflower or grape seed oil. The study did not find any association between consuming corn oil, peanut oil, lard, meat or wine and lowering risk of dementia.
"While we've identified dietary patterns associated with lowering a person's risk of dementia or Alzheimer's, more research is needed to better understand the mechanisms of these nutrients involved in these apparently protective foods," said Barberger-Gateau.Source :