Scientific evidence linking declining mental function with a typical modern diet is increasing. High blood pressure, obesity, diabetes, and high cholesterol levels are all promoted by a modern diet and all appear to speed up the loss of cognitive abilities with age and may contribute to the development of Alzheimer’s disease. An elevated homocysteine level is yet another diet-related risk factor for cardiovascular disease that is also believed to increase the risk of Alzheimer’s disease and promote the loss of mental function. Elevated homocysteine levels can result from an inadequate intake of B-vitamins and too much animal protein, which is rich in L-methionine.

A study of 321 men with an average age of 67 looked at the correlations between homocysteine and B-vitamins and measures of mental function. Researchers found that both elevated homocysteine levels and low levels of B-vitamins were independently correlated with a decline of mental performance.1 This is really not surprising because elevated homocysteine or its metabolites have been shown to be toxic to blood vessels and neurons. The same B-vitamins needed to metabolize homocysteine are also needed by brain cells to make neurotransmitters and structural proteins.It is increasing clear that a modern diet full of fatty and processed meats, eggs, fatty dairy products, and refined grains and sugars and high in salt promotes disease in virtually every organ of the body – including the brain.Bottom Line: More research is needed to further delineate the roll played by different dietary variables in the promotion of brain diseases as well as declining mental function with age. However, there is sufficient evidence to encourage people who wish to retain their mental function to eat a diet lower in salt, saturated fat, cholesterol, trans fat and L-methionine. Consuming a lot more whole fruits, vegetables, whole grains and beans, fortified nonfat milk or soymilk, and a modest amount of seafood should prevent or at least slow much of the loss of mental function for so many older Americans.By James Kenney, PhD, RD, FACN.1. Am J Clin Nutr. 2005;82:627-35