A study into the relationship between dietary fat intake and its impact on Alzheimer’s has found that dietary fat, especially saturated fat, contributed to the risk of Alzheimer’s disease, and the effects were independent of other nutrients.
Saturated fats are typically found in animal-based foods such as beef, pork, poultry, full-fat dairy products, eggs and tropical oils such as coconut and palm oil.
According to the World Health Organization (WHO), there are around 55 million individuals with dementia worldwide. Alzheimer’s disease contributes to 60–70% of dementia cases and is a debilitating and ultimately fatal disease with a survival time of about 3–6 years after diagnosis.
Addressing the potentially modifiable risk factors is essential for the prevention of Alzheimer’s disease. Dietary fat intake, including saturated fat and polyunsaturated fat (PUF), has been increasing over the past few decades among Westerners.
The potential adverse effect of dietary fat intake on health is getting more and more attention.
This Mendelian randomisation study noted that previous observational studies have produced conflicting findings on the relationship between fat intake and Alzheimer’s disease. A meta-analysis of cohort studies up to 2018 reported that only saturated fat intake was associated with a higher risk of Alzheimer’s disease: no association was observed between total fat and PUF intakes and Alzheimer’s disease.
However, considering that randomised controlled trials are expensive and time-consuming, Mendelian randomisation is an optimum choice to infer a causal effect.
The mechanisms underlying the causal linkage between fat intake and Alzheimer’s disease may involve several pathways, the study authors noted.
Higher fat intake induces the release of inflammatory factors, such as tumour necrosis factor-alpha (TNF-α) and interleukin 6 (IL-6), which could trigger gliosis and neuroinflammation, leading to neurologic illnesses.
Over-intake of fat also contributes to brain degeneration. The glycerophospholipids in the neuronal membrane are prone to lipid peroxidation.
Insulin resistance is another potential mediator connecting fat intake and Alzheimer’s disease. Saturated fat intake can increase insulin resistance immediately, and brain insulin resistance is an early and common phenomenon of Alzheimer’s disease that leads to cognitive decline.
Overall, the findings provide empirical support that reducing dietary saturated fat intake is beneficial for preventing and managing Alzheimer’s disease.
