Alzheimer's is a neurodegenerative disease for which, at present, there are only treatments in order to slow its progression. The problem with Alzheimer's is that until now the causes were not well defined and therefore the possibility of action was limited. What has been observed and studied so far has allowed us to state that accumulation of beta amyloid and tau protein plaques in the brain is the distinctive feature of Alzheimer's but what could actually cause the onset of this disease was not clear, at least until today.
Neuroinflammation, the key upstream mechanism of Alzheimer's
Researchers knew until now that there was a missing piece in the puzzle of our knowledge about Alzheimer's thanks to the observation that accumulations of beta amyloid protein plaques may be present in the brain of people who will never develop Alzheimer's. Well, very recent scientific research seems to have finally shed light on this aspect, paving the way for future treatments aimed at preventing and treating Alzheimer's. What the University of Pittsburgh researchers led by Dr. Pascoal observed, and which can be read in the article just published in the prestigious journal Nature Medicine, is that neuroinflammation, namely inflammation affecting the brain, is the real key upstream mechanism that can cause the disease to explode (Pascoal et al, Nature Medicine, 2021). However, chronic cerebral inflammation alone is not enough to trigger Alzheimer's. The simultaneous presence of accumulations of beta amyloid proteins and neuroinflammation is required, which thus stimulates a further accumulation of beta amyloid proteins and tau proteins, effectively causing Alzheimer's disease. What has been observed paves the way for very promising treatments for this disease. But while we wait for science and medicine to take further steps forward, what is in our power to do to counteract neuroinflammation? In this case too, help comes from the diet.
Nutrients against neuroinflammation
The omega 3 fatty acids, which can be found in fatty fish, but also in chia seeds and flax seeds, are particularly beneficial for countering neuroinflammation (Devassy et al, Adv Nutr, 2016). Then, some vitamins show an interesting action aimed at counteracting neuroinflammation, such as vitamin C, contained in citrus fruits, green and red peppers, strawberries, tomatoes, broccoli, Brussels sprouts and green leafy vegetables (Chambial et al, Indian J Clin Biochem, 2013). This link is even clearer when we consider that low levels of vitamin C have been observed in people with Alzheimer's (Monacelli et al, Nutrients, 2017). Also vitamins B2, present in milk and dairy products, eggs, brewer's yeast and green leafy vegetables, B6, which is found in poultry, fish, spinach and legumes, B12, which is present in meat, eggs, milk and dairy products, and folate, contained in green leafy vegetables, legumes and eggs, have been shown to help reduce the release of pro-inflammatory substances, counteracting cerebral atrophy and lowering the risk of developing Alzheimer's (Vasefi et al, J Alzheimer Dis Rep, 2019). Vitamin D, which we synthesize when we sunbathe but also contained in mushrooms, cheeses, eggs and some fish such as anchovies and mackerel, and vitamin E, contained in walnuts, almonds, seeds and avocados, counteract neuroinflammation (Vasefi et al , J Alzheimer Dis Rep, 2019). Not to forget the antioxidants, including polyphenols, of vegetables and fruits, in particular of berries such as strawberries, raspberries, blueberries and blackberries (Businaro et al, Curr Alzheimer Res, 2018).
An alteration of the intestinal microbiota, which is the set of bacteria that populate our intestine, has also been shown to amplify neuroinflammation and accelerate neurodegeneration (McGrattan et al, Curr Nutr Rep, 2019). Hence the importance of taking probiotics, in the form of supplements or yogurt that clearly show it on the label, and prebiotics, contained in onion, garlic, leeks, asparagus, honey, banana, tomato, rye and beans, to support good intestinal bacteria.
Turmeric deserves a separate chapter. The active ingredients of turmeric, in fact, are able to overcome the barrier that exists between blood and brain and act by reducing the accumulation of beta amyloid plaques and neuroinflammation (Sinyor et al, J Alzheimers Dis Rep, 2020). To ensure that the active ingredients of turmeric, however, are made available to the body, a good choice is to associate turmeric with a fat, such as extra virgin olive oil, and black pepper. Therefore, mixing a teaspoon of turmeric in oil and adding a grind of black pepper is an excellent, neuroprotective and anti-inflammatory, dressing for salads.
The role of diet
Therefore, as is clear from the previous paragraphs, we are not talking about a single food, but about a synergy of foods that act together to counteract neuroinflammation with an even more powerful action than single foods taken alone. This is why it is important to follow a healthy and varied diet, which can guarantee the supply of beneficial nutrients for the brain. For example, the Mediterranean diet and the DASH diet were found to be able to counteract neuroinflammation (McGrattan et al, Curr Nutr Rep, 2019). The Mediterranean diet is characterized by a high intake of fruit, vegetables, whole grains, nuts and legumes, a moderate intake of fish, poultry and alcoholic beverages, and a low intake of red and processed meat. The main source of fats in the Mediterranean diet is given by extra virgin olive oil. The DASH diet, developed to combat hypertension, is characterized by a high intake of fruit, vegetables, whole grains and dried fruit, does not involve the consumption of alcohol and places a lot of emphasis on preferring low-fat and low-sodium foods. Instead, the Western-style diet, rich in sugars and refined grains, is pro-inflammatory, stimulating the release of substances that trigger inflammation and make it chronic. Not only that, the Western-style diet can cause alterations in the microbiota, which in turn can induce neuroinflammation (Wieckowska-Gacek et al, Aging Research Reviews). A high-fat diet, such as lard, can also increase neuroinflammation and worsen cognitive function as well as cause overweight (Pistell et al, J Neuroimmunol., 2010).