Elderly people who eat fish or seafood at least once a week are at lower risk of developing dementia, including Alzheimer's disease. Is it the fish, or would you get the same results with fish oil, assuming it had a balanced ration of DHA to EPA? After all, the fish oil may be purified, but the fish could contain higher mercury levels. A fascinating study is the "Fish, meat, and risk of dementia: cohort study," | BMJ - BMJ.com, because the researchers found a link between eating fish and fewer incidences of dementia, but no link between eating meat and fewer cases of dementia.
You may wish to check out studies such as: "Dietary fish and meat intake and dementia in Latin America, China, and India: a 10/66 Dementia Research Group population-based study."
Or see an older study, "Dietary fat intake and the risk of incident dementia in the Rotterdam Study, published in the Annals of Neurology in 1997. And then there's the study, "Review Fatty acid intake and the risk of dementia and cognitive decline: a review of clinical and epidemiological studies."
The Rotterdam study found similar results but had a much shorter follow up (mean 2.1 years), according to the study, "Dietary fat intake and the risk of incident dementia in the Rotterdam study."
And there are pretty good studies from two decades ago such as, "Dietary links to Alzheimer's disease: 1999 update," published in the Journal of Alzheimer Disease,1999;1:197–201. [PubMed]. (Author is Grant WB.), and the study, "Fatty acid intake and the risk of dementia and cognitive decline: a review of clinical and epidemiological studies," published in the Journal of Nutrition Health Aging. 2000;4:202–207. [PubMed]. (Author is Kalmijn S.). Or see, "Fish, meat, and risk of dementia: cohort study."
One study on dementia and diet noted that the first consequences of dementia on everyday living can appear three years before diagnosis. And the researchers wanted to find out whether poor dietary habits could be a consequence rather than a cause of cognitive decline in the Rotterdam participants.
In addition to providing vascular protection, the n-3 fatty acids contained in fish oils could reduce inflammation in the brain and may have a specific role in brain development and regeneration of nerve cells
The scientists also noted that healthy dietary habits acquired in infancy could be associated with achievement of higher education. Highly educated people might also adhere more closely to dietary recommendations on fish consumption. You also may wish to check out the study, "Dietary fat intake and the risk of incident dementia in the Rotterdam Study, published in the Annals of Neurology in 1997.
What the study noted was that a high intake of saturated fat and cholesterol and a low intake of polyunsaturated fatty acids have been related to an increased risk of cardiovascular disease. Cardiovascular disease has been associated with dementia.
So the researchers investigated the association between fat intake and incident dementia among participants, age 55 years or older, from the population-based prospective Rotterdam Study.
Food intake of 5,386 nondemented participants was assessed at baseline with a semiquantitative food-frequency questionnaire. At baseline and after an average of 2.1 years of follow-up, we screened for dementia with a three-step protocol that included a clinical examination. You may wish to check out, "Review Fatty acid intake and the risk of dementia and cognitive decline: a review of clinical and epidemiological studies." Or see, "Dietary fat intake and the risk of incident dementia in the Rotterdam Study," or "Review Fatty acid intake and the risk of dementia and cognitive decline: a review of clinical and epidemiological studies."
In the study, "Fish, meat, and risk of dementia: cohort study," researchers looked at the role of dietary fat in dementia. The researchers evaluated whether there is a relation between consumption of fish (rich in polyunsaturated fatty acids) or meat (rich in saturated fatty acids) and risk of dementia.
During the seven years of follow up, 170 new cases of dementia occurred, including 135 cases of Alzheimer's disease, the study notes. If you look up the study, you may notice that the table in that study shows a significant trend between an increasing consumption of fish or seafood and decreasing incidence of dementia.
The researchers also found that the frequency of fish or seafood consumption was higher in the participants with higher education. Interestingly, it was fish (or fish oil) that made the difference because the researchers found no significant association between meat consumption and risk of dementia.