Following a diet low in saturated fats and low glycemic index seems to modulate the risk of developing dementia, a disease that ends up becoming Alzheimer's, although changing these eating patterns may not protect those who already suffer from cognitive difficulties. This is demonstrated by a study developed by American researchers and published this June in Archives of Neurology.

Previous research had already suggested the existence of links between diet and cognitive ability, according to the authors of this last work. The health situations in which those affected present insulin resistance (The inability of the body to use insulin effectively) -like obesity, type 2 diabetes, cardiovascular disease, or high cholesterol levels-have been associated with "pathological brain aging."

However, studies conducted on specific foods had not found conclusive evidence of the existence of an influence on Alzheimer's risk. "Thus," the authors write, "a more promising approach to the study of dietary factors in Alzheimer's may involve the use of dietary interventions complete, with greater ecological validity, and preserve the nutritional environment in which the consumption of fat and carbohydrate occurs ".

The results of the study could show that dietary interventions are not as effective in late stages of cognitive decline

The team of Jennifer L. Bayer-Carter, of the Veterans Affairs Puget Sound Health Care System, in Seattle, set out to compare a diet rich in saturated fats and simple carbohydrates -associated with type 2 diabetes and insulin resistance- with a diet low in saturated fats and simple carbohydrates. The interventions were called HIGH and LOW, respectively.

The authors of the study evaluated the effects of these two diets on 20 healthy older adults and 29 older adults who suffered mild amnestic cognitive impairment (aMCI), which means that they experienced some memory problems. Advanced aMCI is often considered a precursor to Alzheimer's.

In a randomized controlled trial that lasted four weeks, a total of 24 participants followed the HIGH diet and another 25 the LOW diet. The researchers studied the behavior of these participants with memory test, as well as their levels of biomarkers -The biological substances indicative of Alzheimer's-, such as insulin, cholesterol, blood glucose levels, blood lipid levels and components of cerebrospinal fluid (CSF).

The results of the study were different for the group that had aMCI and for the group of healthy participants. In the latter group, the LOW diet reduced some of Alzheimer's CSF biomarkers, as well as their total cholesterol levels. However, among individuals such as aMCI, the LOW diet increased the levels of these biomarkers.

The LOW diet improved the behavior in delayed visual memory tests, both in healthy participants and those with impaired memory, but did not affect the scores in other cognitive indicators.

These results indicate that "for healthy adults, the HIGH diet moved the CSF biomarkers in a direction that may characterize a pre-symptomatic Alzheimer's state." The authors believe that the different results obtained in participants with aMCI could demonstrate that dietary interventions are not as effective in late stages of cognitive decline.

"The therapeutic effects of a long-term dietary intervention could be a promising avenue of exploration," the researchers write, adding that, in addition, "identifying the pathophysiological changes that underlie the effects of diet can reveal important therapeutic targets that can to be modulated through directed dietary or pharmacological interventions ".

Reducing Alzheimer’s Disease Risk Video – Brigham and Women’s Hospital (November 2019).