Does a high-fat diet raise the risk of Alzheimer's disease?

Various research has linked a high-fat diet to an increased risk of Alzheimer's disease, the most common type of dementia. In the UK, one in every 11 people over 65 have dementia, with the number only increasing.

Lifestyle factors like smoking and alcohol, a lack of exercise and an unhealthy diet (including studies exploring the effect of a high consumption of saturated fat), have all been cited as possible risks for Alzheimer's.

Looking specifically at the latter, the mechanisms of how a high-fat diet actually increases the chances of the disease have been unclear. Recent research published in Nutrients, however, unearthed changes in molecular markers related to Alzheimer's in mice fed a high-fat diet, which could help explain the association.

Comparing mice fed normally and those fed a 60% high-fat diet for six months, the mice on the unhealthy diet gained more weight, had worse glucose (blood sugar) and insulin metabolism. At various stages, researchers also found that the high-fat diet aggravated their learning and memory, along with increasing 'neuroinflammation', beta-amyloid (found in the brain's of people with Alzheimer's) production and plaque burden.

As well as metabolic changes, the mice on the high-fat diet showed differences in miRNA (molecules). In the study, the researchers said, "These findings support an active role of these miRNAs in the progression of neurodegeneration aggravated by the metabolic misbalance produced by consuming a high-fat diet".

How reliable is this latest development?

Dr. Lawrence Cunningham, a retired GP and medical contributing expert at UK Care Guide, tells Yahoo UK, "The recent studies on mice offer an insight into how high-fat diets might influence the development of Alzheimer's. These studies have shown that such diets can lead to increased brain inflammation and changes in brain chemistry that are conducive to Alzheimer’s disease.

"However, translating these findings to humans is complex! Mice are not humans, and their shorter lifespans and different metabolism can lead to different effects. Therefore, while these studies are informative, they are not, in my view, definitive."

What we know about the link between a high-fat diet and Alzheimer's

So, what does Dr. Cunningham think generally on whether this type of diet can increase risk of the disease?

"A high-fat diet, particularly one rich in saturated fats, can exacerbate the risk factors for Alzheimer's by promoting inflammation and oxidative stress. Both of these processes can damage brain cells and contribute to the accumulation of amyloid plaques, which is regarded as a hallmark of Alzheimer’s disease. In my practice, I always recommended a balanced diet rich in antioxidants and anti-inflammatory foods to help mitigate these risks."

Dr. Cunningham basis this on what we can infer so far from studies, as well as his own personal patient experiences. "I've noticed in the past that patients on high fat diets can sometimes have more issues with inflammation and insulin resistance, which are linked to Alzheimer's. Researchers, from studies I've seen, have found similar connections.These have shown that high-fat diets can worsen these risk factors. While these studies give us some solid clues, more research is still needed to get the fuller picture."

How does obesity and type 2 diabetes play a role?

With high-fat diets also causing other health conditions, that in turn can be linked to Alzheimer's, but why is this? "Obesity, type 2 diabetes, and hypertension are known to compromise the body's health, which has direct and indirect effects on brain function," says Dr. Cunningham.

"From what I've observed, patients with well managed diabetes and blood pressure tend to exhibit slower cognitive decline compared to those with poorly managed conditions. The systemic nature of these health issues means that they don't just affect one part of the body but have widespread impacts, including on the brain."

Can a lower-fat diet help reduce Alzheimer's risk?

"Switching to a lower-fat diet, particularly one that reduces saturated fat and includes healthy fats like omega-3 fatty acids, could indeed be beneficial in reducing the risk of Alzheimer's. Such diets improve vascular health and reduce inflammation, which are critical in preventing cognitive decline," says Dr. Cunningham.

So, while more research is needed to prove the link definitively, it seems we do need to listen to the mounting research. And eating a lower-fat diet (which doesn't mean fat needs to be eliminated completely, as there are also healthy fats, and it's about what you eat most of the time that matters, not some of the time) along with a healthy, balanced diet, never hurt anyone.

For advice on how to eat less saturated fat, visit the NHS website.

• Read more: Is it healthier to go plant-based? How do processed foods affect this? (Yahoo Life UK, 7-min read)

• Read more: The early signs of Dementia: 'I thought my nan was grieving, but it was Alzheimer's' (Yahoo Life UK, 8-min read)

• Read more: Signs of Alzheimer’s as thousands to trial new blood test for dementia (Yahoo Life UK, 5-min read)

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