What foods should we bring to the table to keep neurodegenerative diseases such as Alzheimer’s at bay? And what are the ones that would increase the risk of its onset? A new study on the role of diet in the risk of developing dementia has identified regular consumption of fruit, legumes, nuts, omega-3 fatty acids, vegetables and whole grains as the ideal dietary pattern to combat dementia. On the contrary, the risk increases for diets rich in processed foods, rich in fats and sugars. Yet another confirmation of the value of the Mediterranean diet and of the fact that there are factors, such as obesity and diabetes, on which it is possible to intervene to combat dementia. The data comes from‘analyses published by Journal of Alzheimer’s Disease.
by Sara Carmignani
Diet models compared
The authors of this new study (a review on the topic), Wiliam B. Grant of the Sunlight, Nutrition and Health Research Center in San Francisco, and Steven M. Blake of the Mau Memory Clinic in Wailuku, Hawaii, relied on observational studies which compared different dietary models. There are four main groups considered: the so-called Western one (in which 70% of calories come from foods of animal origin, oils, fats and sweeteners), the DASH Diet (Dietary Approaches to Stop Hypertension rich in whole grains, fruit, vegetables, oils vegetables, legumes, low-fat dairy products, nuts, fish, poultry and very small or no quantities of red meat), the MedDI (Mediterranean diet rich in olive oil, fish, bread and cereals, fruit, vegetables, legumes, moderate quantities of dairy products and poultry, and small amounts of red meat) and MIND (based on the Mediterranean and DASH diets).
It emerged that diets such as DASH and MIND – largely inspired by the Mediterranean diet – would be able to reduce the risk of Alzheimer’s onset by 40-50% compared to the Western diet. A dietary model based on vegetables, fish, legumes, cereals, fruit and predominantly white meat, typical of our areas and of some Asian countries such as China, Japan and India, would in fact carry out a protective action, so much so as to also counteract the advancement of cognitive decline. But it would also lower the risk of contracting comorbidities, first and foremost diabetes and obesity.
When the disease progresses with a certain type of diet
From the studies analyzed it emerged that when the consumption of meat, sugars and fats increases, the risk of dementia increases instead. One of these studies has in fact found that in Japan between 1985 and 2010 the incidence of dementia increased after a greater consumption of alcohol, meat and animal products (with a stronger correlation in the 15-25 year interval), passing from 1% in 1985 to 7% in 2008.
Diet and Alzheimer’s: risk factors
But what are the biological mechanisms affected by diets associated with a higher risk of developing Alzheimer’s? They are many and different, as the authors explain in detail, and the first in order of importance concerns obesity. Excess fat, which increases the production of free radicals, can in fact cause the breakdown of the blood-brain barrier. When this happens, toxins and pathogens can cause inflammation of the central nervous system and damage neurons. From a recent one study of the Montreal Neurological Institute Hospital of McGill University, it also emerged that the neuronal changes in obese people are not so different from those that occur in those suffering from Alzheimer’s. Both diseases would in fact be able to atrophy the brain in a similar way, influencing the cortical thinning of the gray matter. And given that obesity rates globally continue to grow, Blake and Grant highlight how this pathology could be a useful indicator for predicting the incidence of dementia.
by Sara Carmignani
Then there are diabetes and insulin resistance. The latter, typically associated with the excessive consumption of refined carbohydrates and sugars, decreases the ability of brain cells to respond to insulin (a fundamental hormone for the absorption of glucose), thus altering the survival and functionality of neurons. Even excessive quantities of copper, iron and zinc (contained in large quantities in meat) would favor accumulations of beta-amyloid in the brain. Other risk factors are hyperhomocysteinemia (the high concentration in the blood of homocysteine, an amino acid that derives from the enzymatic transformation of methionine contained in protein foods), which can cause clots and damage brain tissues, and the high concentration of end points of advanced glycation (molecules produced by the interaction between sugars, groups of proteins, nucleic acids and lipids which can prevent neurons from functioning properly, contributing to the formation of amyloid plaques) present, for example, on the toasted surfaces of fried foods. Finally, the risk factors also include high concentrations of trimethylamine N-oxide (metabolite that derives from the intestinal microbiota), an indicator of a diet too rich in animal foods, which, according to experts, can cause the aggregation of the protein tau and beta-amyloid.
Eating well costs money
But if it is true that a diet richer in fibre, vitamins and minerals can help lower the risk of developing dementia, it is equally true that changing habits is not always easy. And above all, strictly following this dietary pattern is decidedly expensive and out of reach for low-income people, especially in some regions of the world. It is certainly more so than the Western diet: which is why, as the authors of the study write, those who cannot afford it are more exposed to the risk of suffering from Alzheimer’s. This is a social inequality which, experts underline, would require a position and intervention by government authorities and the world of industry.