A review article by Polish scientists analyzed how diet changes gut bacteria and potentially affects Alzheimer's risk, as well as which foods may help slow brain aging. An analysis of the available evidence, published in Nutrients, suggests that diet may play an important role in preventing Alzheimer's disease.
Experts analyzed how nutrition affects the intestinal microbiota and, through it, processes in the brain, including inflammation and lipid metabolism.
Imagine your gut and your brain as two cities connected by a superhighway. This highway is constantly sending signals in both directions. Billions of bacteria in your gut, like little factory workers, process the food you eat and produce various substances. Some of these substances are useful “messages” for your brain, while others are harmful and can cause problems.
The balance of microbes determines whether protective short-chain fatty acids will be produced or, conversely, toxic metabolites that accelerate neurodegeneration.
That is, when good bacteria get the right food (like fiber from vegetables), they produce substances that fuel and protect our cells and reduce inflammation throughout the body. But when bad bacteria, which feed on sugar and unhealthy fats, dominate, they create toxins that can enter the bloodstream and damage the brain over time, accelerating its aging.
The Mediterranean diet, DASH, and their hybrid MIND showed the most beneficial effects. These diets are rich in fiber, omega-3s, and polyphenols, support the growth of beneficial bacteria, and are associated with a lower risk of cognitive decline.
In other words, a diet based on vegetables, fruits, whole grains, fish, and olive oil is a feast for our good bacteria. Fiber is their favorite food, omega-3 fatty acids (from fish) fight inflammation, and polyphenols (antioxidants from berries, tea, and vegetables) protect cells from damage. When microbes are happy, they are better able to protect both the gut and the brain, helping to keep our minds sharp for years to come.
Among the approaches discussed, a modified “keto-Mediterranean” regimen that combines ketosis with an antioxidant profile while seeking to preserve fiber intake stands out as a promising area of research.
It's an interesting experiment: taking the benefits of the keto diet (where the body uses fat as its primary fuel, which can be beneficial for the brain) and combining them with the richness of the Mediterranean diet. The goal is to get double the benefits without depriving the beneficial bacteria of their main food: fiber.
In contrast, a Western diet, based on processed foods and excess sugar and fat, reduces microbiota diversity and increases levels of inflammatory molecules.
Here, it's the other way around: fast food, sweets, and processed foods are food for the “bad guys” in our gut. They start to dominate, and the diversity of good bacteria drops. Imagine that instead of a colorful flower garden, you're left with a field overgrown with one type of weed.
This exacerbates damage to the gut-brain barriers, accelerating the development of dementia.
The wall of our intestines is a thick fence with guards. The wrong food acts as a destructive force: it reduces the number of “good guards” (beneficial bacteria) and makes holes in the fence. Through these holes, harmful substances and inflammatory molecules can leak into the bloodstream, which then travel to the brain and damage its own protective barrier. It's like opening the gate to enemies, which accelerates the destruction of brain cells.
Scientists also note the potential of prebiotics, probiotics, and seaweed polyphenols to restore eubiosis and curb inflammation.
To be clear: probiotics are the beneficial bacteria themselves (like in yogurt or sauerkraut), like a landing party of new soldiers for your intestinal army. And prebiotics are food for them (fiber from onions, bananas, garlic), their “dry rations” that help them grow and multiply. Eubiosis is the very ideal balance when there are enough soldiers in the army and they are well-fed.
In doing so, they emphasize the need for a personalized approach and clinical trials to confirm the causal relationship between diet, microbiota, and Alzheimer's risk.
Why is this important? Because each person's gut microbiome is as unique as a fingerprint. What works perfectly for one person may not work as well for another. Scientists need to prove with certainty that diet is the one that causes changes in the brain through bacteria, and not just one of many factors that exist in parallel.
