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Diet and age-related loss of mental (cognitive) function
(February 2007)

There are increasing numbers of studies on the role of diet in reducing the loss of mental (cognitive) functioning or the occurrence of dementia in older people.  A lot of the interest has focused on intake of fish and omega-3 polyunsaturated fatty acids (which are found in oily fish - CLICK HERE for a list of oily fish with high omega-3 fatty acid content).  A new study from the Italian Longitudinal Study on Aging provides some interesting information.  A single detailed questionnaire instrument was used to assess mental function.  Two hundred seventy-eight men and women, average age 73 years, had dietary intake and mental function analyzed at enrollment.  One hundred eighty-six had a repeat mental function examination four years later, and 95 had a third mental function examination eight years after enrollment.  The extent of cognitive function decline was reduced significantly by both dietary polyunsaturated and monounsaturated fatty acids.  The dietary sources of polyunsaturated fatty acids were primarily soy and sunflower oils, butter, cheese, fish, and olive oil.  Olive oil was the major source of monounsaturated fatty acids.

The authors concluded “in this prospective population-based study on older nondemented subjects with a typical Mediterranean diet, high monounsaturated and polyunsaturated fatty acid intakes appeared to be protective against age-related cognitive decline”.

Commentary: This is a nice study, but there are issues:

- The number of people participating in the study was relatively small.

- There can be questions about the single questionnaire selected to measure mental function.

Additionally, there are only a small number of other studies that are similar and the results are not entirely consistent.

We need more long-term studies.

At present, no conclusions are possible, but it is clear the Mediterranean diet (high in vegetables, fruits, legumes, fish, whole grains, olive oil, nuts, and also including moderate wine intake) is a healthy diet that lowers the risk of coronary heart disease and, as noted here, possibly lowers the risk of age-related mental function decline.  In regard to heart disease, it is probably the totality of the diet that produces the benefit, though some experts think the olive oil plays a particularly important role.  In regard to reducing mental decline and even Alzheimer’s, there has been a particular interest in oily fish and omega-3 polyunsaturated fatty acids.

Solfrizzi, V., et al.  Dietary intake of unsaturated fatty acids and age-related cognitive decline.  Neurobiology of Aging.  Vol 27 (October) Pgs 1694-1704.  2006.