Vegetables and Cognitive Decline
Recent studies have demonstrated a number of associations between certain nutrients and prevention of age-associated cognitive decline. Vitamin E, vitamin B12, niacin, and folate have been associated with this preventative effect. A recent study was performed in Chicago to examine the effects of fruits and vegetables in the prevention of age-related cognitive decline.
In a study by Morris et al.,1 4,398 older individuals (mean age 73.6 years) were followed for 6 years, their diets were assessed with a food questionnaire. At the beginning, at three years and conclusion (six years) of the study period, cognitive assessments were performed.
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Comparison of the top 20% of fruit consumers versus the bottom 20% showed no difference between the two groups on cognitive testing. There was also no difference in combined fruit and vegetable intake on cognitive decline.
However, there was a trend (meaning the result did not meet statistical significance for a clear difference but was very close and met significance for a trend) towards less cognitive decline in the group that ate the most vegetables (to 20% of vegetable consumers versus bottom 20%).
With some statistical analyses the authors claimed that higher intake of vegetables may result in a slower rate of cognitive decline with a reduction of 35%. Based on their study, this conclusion is stretching the facts a bit but nonetheless it is an interesting observation.
Interestingly this data was consistent with the Nurses' Health Study which did demonstrate a trend that higher vegetable consumption but not fruit consumption was associated with less cognitive decline over two years.2
So how many servings of vegetables did these individuals eat. In the high intake group they ate on average between 3.4 and 8.2 servings per day. In the low intake group between 0 and 1 servings per day.
So what does this all mean? Increased vegetable consumption may have a protective effect against cognitive decline and dementia. It appears to be a relatively small effect at least over a six year period. Of course cognitive decline is a life long process so would there be a larger effect over 50 or even 70 years ... hard to say. However, since there are few benefits to not eating vegetables, it's probably wise to eat a well balanced diet with ample vegetable servings each day.
Dr. Lawrence Korngut, M.D.
Chief Neurology Resident
London Health Science Centre
London, Ontario
1 Morris MC et al., Associations of vegetable and fruit consumption with age-related cognitive change. Neurology 2006;67;1370-1376.
2 Kang JH et al., Fruit and vegetable consumption and cognitive decline in aging women. Annals of Neurology 2005;57:713-720.