Previous research has suggested various links between what you eat and your risk of developing dementia that proceeds to Alzheimers disease. But trials of specific foods for defense against dementia have mostly proven frustrating. Now a small, relatively brief clinical trial might point to a different kind of answer: Overall dietary changes, not just adding or subtracting a single food, could affect the risk of dementia and Alzheimers. In particular, the study found that in healthy people, a diet low in saturated fat and simple carbohydrates improved biomarkers associated with the risk of developing Alzheimers.
A more promising approach to the study of dietary factors in Alzheimers disease might entail the use of whole-diet interventions, noted Jennifer L. Bayer-Carter, MS, from Veterans Affairs Puget Sound Health Care System, and colleagues. Our study supports further investigation into the possibility that consumption of a diet high in saturated fat and simple carbohydrates may contribute to pathologic processes in the brain that increase the risk of Alzheimers disease. Conversely, diets low in saturated fat and simple carbohydrates may offer protection against Alzheimers disease and enhance brain health.
Bayer-Carter and colleagues evaluated effects of two different diets in 20 older adults who were healthy and 29 older adults who had amnestic mild cognitive impairment (aMCI), meaning they experienced some memory problems- a condition often considered a precursor to Alzheimers disease. One regimen, dubbed the LOW diet, was low in saturated fat and simple carbs (such as those with a high glycemic index). The alternative HIGH diet emphasized foods high in saturated fats and simple carbs.
After four weeks, healthy participants on the LOW diet decreased biomarkers in cerebrospinal fluid associated with Alzheimers, as well as total cholesterol. The HIGH diet, by contrast, moved biomarkers in a direction that could characterize a presymptomatic stage of Alzheimers.
An opposite result was seen, however, when testing biomarkers among the aMCI subjects who were already experiencing memory problems. In this group, the LOW diet actually increased markers of Alzheimers disease, such as levels of amyloid-beta protein in cerebrospinal fluid.
All those on the LOW diet, both the healthy and aMCI group, improved performance on delayed visual-recall tests of memory, but not on other cognitive measures.
The sometimes-contrary outcomes spotlight the complex nature of dementia and Alzheimers, researchers commented. The different results in participants with aMCI may show that dietary interventions are not as effective in later stages of cognitive impairment. Bayer-Carter and colleagues also cautioned that their study wasnt long enough to evaluate the effects of whole-diet changes on cognition generally.
These findings might be another reason to cut down on saturated fat and simple carbohydrates-a healthy change for most people regardless of your age.
TO LEARN MORE: Archives of Neurology, June 2011; abstract at dx.doi.org/10.1001/archneurol. 2011.125. The Battle for Your Brain, October 2010 Tufts University Health & Nutrition LetterSpecial Supplement.
What do we know about diet and the risk of dementia and Alzheimers disease?
- Foods rich in vitamin E may help stave off mental decline with aging. In results from one study tracing 5,395 people ages 55 and up for nearly a decade, researchers reported that those with the highest dietary intake of vitamin E from food were less likely to develop dementia and Alzheimers than those consuming the least. The polyunsaturated fats found in liquid vegetable oils and some spreads (not those containing partially hydrogenated fats) are one healthy way to get dietary vitamin E.
- Another study found a link between blood levels of vitamin D in 858 older Italian adults and risk of cognitive decline. Vitamin D may help prevent the degeneration of brain tissue, researchers speculated.