High carbohydrate intake and cognitive impairment in the elderly

An issue of Neurosciences Update published in 2012 by the Mayo Clinic  contains a Research Highlight on the Association Between Macronutrient Intake and Risk of Dementia. The authors studied the 128-item food-frequency questionnaires of 937 cognitively normal elderly, 2oo of which later developed mild cognitive impairment (MCI) or dementia.

Findings showed that among the 937 participants who were cognitively normal at baseline, MCI or dementia developed in 200 and that the risk of either condition was increased in participants with dietary patterns showing a high percentage of carbohydrate intake and reduced in those with a high percentage of fat and protein intake. The authors concluded that a diet high in carbohydrates and low in fats and proteins may increase the risk of MCI or dementia in elderly persons (Roberts et al. J Alzheimer’s Dis. 2012;32[2]:329-39).

The research study, freely available online, does not lists the type of carbohydrates consumed by the participants.  From the food-frequency questionnaires, the authors

… computed the proportion of total daily energy derived from total carbohydrates (% carbohydrate), fat (% fat), and protein (% protein); from carbohydrate components (sugar, non-sugar carbohydrate, fiber); and fat components (polyunsaturated fatty acids [PUFA], monounsaturated fatty acids [MUFA], saturated fats [saturated fats], and trans-fatty acids), and ranked participants by quartiles of intake.

The researchers suggest several mechanisms for the impact of high carbohydrate intake on cognitive function in the elderly, among them:

High carbohydrate and sugar intake may adversely affect cognition through several mechanisms. Hyperglycemia and diabetes may contribute to increased formation of advanced glycation endproducts (AGE), upregulation of the soluble receptors for AGEs, and may generate oxidative stress which in turn, enhances AGE formation. AGEs and oxidative stress have also been associated with greater cognitive decline and with AD through effects on amyloid and tau metabolism.

The increased risk of MCI with lower intake of fats and proteins may involve non-energy related pathways. Fat and protein intake may be required for the integrity of neuronal membranes and fats for the integrity of the myelin sheaths in the brain.

Bottom Line: Don’t let your grandparents skip out on high quality sources of fat and protein.