Alzheimer’s disease is a progressive neurodegenerative disease that results in a decline in cognitive ability. Unfortunately, there are no effective treatments for this condition. However, nutritional interventions have been identified as measures that can slow the progression of the disease.
The researchers conducted a search for randomized clinical trials, systematic reviews, and meta-analyses published between 2018 and 2022 in the PubMed, Web of Science, Scopus, and Cochrane Library databases. A total of 38 studies were identified, of which 17 were randomized clinical trials, and 21 were systematic reviews and/or meta-analyses.
The review found that the Western diet pattern is a risk factor for developing Alzheimer’s disease. In contrast, the Mediterranean diet, ketogenic diet, and supplementation with omega-3 fatty acids and probiotics are protective factors. The protective effect of these interventions is significant only in cases of mild-to-moderate Alzheimer’s.
Low dietary quality is also a risk factor for developing Alzheimer’s, which worsens cognitive performance and verbal fluency. Malnutrition and unintentional weight loss are also associated with an increased risk of mortality in patients with Alzheimer’s disease.
A diet with a high glycemic index or refined carbohydrates is associated with increased accumulation of Aβ peptides in the brain, which is even worse in APOE-ε4 carriers. APOE-ε4 is a genetic risk factor associated with Alzheimer’s and dementia, as well as insulin resistance. The Western diet pattern also increases inflammation levels.
Adherence to the Mediterranean diet has been shown to decrease the risk of dementia by 20%. This diet has also been shown to improve cognitive outcomes, increase gray matter volume, improve memory, and decrease memory decline.
A ketogenic diet has also been shown to be useful in the treatment of Alzheimer’s. It has been shown to reduce oxidative stress and inflammation and reduce the negative effects of altered glucose metabolism in the brain. Additionally, it can improve verbal memory, attention, and overall cognitive function. However, the long-term use of this diet may present risks, so it should be monitored by an expert nutritionist.
Adequate intake of antioxidants in the diet is a factor to consider since Alzheimer’s disease presents with high levels of oxidative stress. Lower levels of vitamin D are associated with worse cognitive performance scores in patients. Vitamin B12 deficiency is also a risk factor for Alzheimer’s. Vitamin E is a powerful antioxidant and an anti-inflammatory agent.
Observational cohort studies have shown that people with Alzheimer’s have significantly lower levels of tocopherols, tocotrienols, and total vitamin E compared to the general population.
Adequate levels of omega-3 polyunsaturated fatty acids, especially EPA and DHA, are associated with slower rates of cognitive decline and reduced risk of dementia. Dysbiosis of the microbiota is a clear risk factor for the development of Alzheimer’s. High-fat diets, the use of antibiotics, or the lack of probiotics and/or prebiotics can also change the composition of the microbiota and therefore be a risk factor for Alzheimer’s disease.
The review found that nutritional interventions only work in patients with mild and moderate Alzheimer’s. Further research is required to draw more definitive conclusions.
Nutritional interventions are good non-pharmacological tools for the treatment of Alzheimer’s disease, and the results of the review showed that they are capable of slowing down the rate of progression of neurodegeneration, improving cognitive function, and improving the quality of life of these patients.