Incidence of mild cognitive impairment (MCI), Alzheimer's disease, and Parkinson's disease is increasing as the mean age of Western populations rises. This article, the second article of a two-part review, assesses the existing scientific literature addressing the role of minerals, phytochemicals, specific grain-based foods, and dietary patterns, with and without grains, to determine whether these foods and their constituents affect the onset or course of these common dementias, as has been alleged in various books, blogs, and other media. Intakes and serum markers of mineral and phytonutrient intakes in many cases have been documented as low or below recommended levels in elderly individuals and patients with MCI, Alzheimer's disease, or Parkinson's disease. However, it is not clear whether adequate intake of these minerals and phytonutrients from all sources, including grains, can impact the onset or course of these dementias. There are few published studies on specific grain-based foods and their relationships to common dementias, and the results have been mixed or shown a dose or total diet effect. Studies have shown an association between whole grain, cereal, and high-fiber grain-based food intakes and lower risk of cognitive impairment and dementias. Results of studies on specific grain-based foods indicate that higher bread intakes, especially high-fiber breads, are associated with better cognitive performance and lower rates of dementia; however, higher than recommended levels are associated with poorer performance and greater risk of impairment. Other studies have shown that high rice intake may be associated with poor cognitive performance but that this may be due to the lack of important components in the diet, rather than solely to rice intake, or to an interaction of the two factors. Studies have also shown an increased risk associated with excess white bread, rice, or indulgent grain intakes when the overall diet is out of balance. The results of most, but not all, studies show that grain-based foods that are eaten as part of a balanced dietary pattern do not increase the risk for developing MCI, Alzheimer's disease, or Parkinson's disease and, in fact, may reduce the risk.
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