Improve your gut health to protect your brain

Beneficial gut bugs produce helpful chemicals, like anti-inflammatory gut wall-protective short chain fatty acids (SCFAs). “Bad” gut bugs produce molecules that promote inflammation, as the immune system, about 70 per cent of which is located in the gut, tries to defend against them. Gradually this harms the delicate gut barrier lining. Then these molecules get into the bloodstream, leading to persistent inflammation as the immune system over-responds. “When inflammation becomes chronic it can spread, affecting blood vessels,” Nandi says. “Over time it can weaken the blood–brain barrier.”

Dr Partha Nandi

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Chronic inflammation can accelerate brain injury and cognitive decline, whether the condition is Alzheimer’s, stroke or Parkinson’s. “Inflammation doesn’t cause every brain disease but it fuels nearly all of them,” Nandi says.

He concedes that, for many, the link between gut and brain health is “a difficult concept because they think of the intestinal system as just to digest food,” but adds, “All of us deep inside, intuitively, feel that our gut and brain are connected.” We’ve all had “butterflies in our stomach” or a “gut feeling”. Now science is catching up, showing there is constant two-way communication between gut and brain — with the gut actually wielding more influence.

How, though? The gut wall contains a vast network of neurons — the same type of cells as in the brain — and our gut microbes can “signal” to these neurons and thereby, as Nandi says, “direct cellular activities elsewhere in the body, including in the brain”. Most of this communication travels via the “gut-brain axis”, especially the vagus nerve, our longest cranial nerve and “a superhighway of information”, Nandi says. Our gut bugs also make neurotransmitters such as serotonin — important in regulating mood, sleep and appetite.

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Regarding our gut bugs’ influence on mood, memory, cognition, motor control and more, he says, “the data is just overwhelming”. In his new book, Heal Your Gut, Save Your Brain, Nandi notes that the gut microbes of patients with Parkinson’s disease typically produce smaller amounts of short-chain fatty acids (SCFAs). Research presented at the European Stroke Organisation Conference in 2022 showed that the gut microbiome can affect stroke risk and neurological recovery. He reports on a study in that same year by King’s College London examining blood and stool samples of 68 people with Alzheimer’s and 68 without. The “Alzheimer’s gut” was distinct, with increased markers of inflammation.

But even if we’re already living with these conditions, we’re not helpless, Nandi says. Improving gut health may help to prevent cognitive decline in stroke patients, for instance. His advice — to his patients and to his kids, aged 12, 13, and 7 — applies to all. If you prioritise and revitalise your gut health not only can you reduce your risk of disease, “you can also bolster your health presently”.

Nutrition is a pillar of gut health (but don’t overdo the protein)

Dr Partha Nandi recommends eating nuts and seeds for a healthier gut

CLAUDIA TOTIR/GETTY IMAGES

“The most powerful weapon we have to bolster gut health is the fork,” Nandi says. But perhaps we consider ourselves healthy, rarely eating pizza — which he calls “an atomic weapon launched straight at the gut” — but forking up large daily helpings of animal protein. Nandi says: “Protein isn’t the enemy but balance matters.”

Consistently eating a high animal-protein, low-fibre diet can starve beneficial fibre-loving microbes and weaken the gut barrier over time, he says. (Eggs and plain yoghurt are part of a “gut-friendly diet”, but keep red meat to once a week max.)

He warns against the “low carb, high protein and build muscle and that’s all there is to it” attitude. “Your gut could be ravaged and you could still have a great-looking body.” Even if you’re eating grass-fed steak rather than burgers, “when you don’t include fibre and complex carbs in your diet, you are still then producing an environment for the microbiome not to thrive”.

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Foods to nourish gut and brain

Heal Your Gut, Save Your Brain was written after the death of Nandi’s beloved, brilliant father. The book is wrought with fierce grief that, following a stroke, rather than spending quality time with his grandkids “that last decade was taken away from him”. He was never ill, Nandi recalls, but he didn’t make gut health “a priority”.

Nandi wants to give us the information he wishes he’d had for his father decades ago — the importance of reducing inflammation by regularly eating probiotics (fermented foods containing beneficial bacteria, such as cottage cheese, kefir, miso, yoghurt, gouda and cheddar) and prebiotics (typically high-fibre foods that feed beneficial gut bugs, such as leeks, onions, garlic, artichokes, bananas, pulses, oats and lentils). Then healthy gut bugs produce chemicals called “postbiotics” such as butyrate and other SCFAs, which support the immune system. “As probiotics break down fibre, they secrete specialty chemicals known collectively as postbiotics,” Nandi writes in the book, emphasising just how crucial fibre is in our diet. Postbiotics play a significant role in supporting the immune system and alleviating the symptoms of irritable bowel syndrome, among other benefits. Nandi also lists foods shown to help prevent and reduce the effect of stroke, such as ginger, melon, oats, soya beans, beans, legumes, beetroot, tomatoes and potassium-rich foods like bananas and spinach.

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When your gut needs attention

Signs that all is well with your gut can include regular bowel movements and what Nandi describes as a “lightness of being”. His father “did have some gastrointestinal symptoms. Not every day but several times a month — bloating and discomfort.” Symptoms of an unbalanced gut — too many bad bacteria, not enough beneficial ones — include gas, bloating, diarrhoea, constipation and cramping. Persistent changes warrant attention. “These symptoms may be a sign that something is awry in your gut health.” And an unhealthy gut microbiome can damage the gut barrier which, Nandi says, “is one cell layer thick, with two mucus layers surrounding it — that’s how susceptible we are”.

It’s informally called “leaky gut”, he says, but the scientific term is “intestinal permeability” — and if particles pass through those small crevices, they “begin the process of inflammation on the other side of the gut, into the blood”. Common symptoms include brain fog, fatigue, headaches, joint pain, acne, chronic diarrhoea or constipation, gas and bloating.

Nandi notes that factors that increase stroke risk — hardening of the arteries, obesity, high blood pressure — can be independently linked to an imbalance in the gut. Constipation is the most common gastrointestinal symptom of Parkinson’s, he says, and it affects more than 50 per cent of patients at some point. Nandi says that people with optimal intakes of vitamin A and carotenoids, vitamin B, folates and vitamin D tend to have a lower risk of Parkinson’s.

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Inflammatory bowel disease: make sure you control your symptoms

This feels nerve-racking — “leaky gut” symptoms are common and nonspecific. And won’t those with, say, ulcerative colitis or Crohn’s worry reading this? While Nandi’s view is better safe than sorry (“I don’t want anyone to think, ‘Well if I have no symptoms I’m fine.’ A lot of things happen subclinically”), he also clarifies: “I don’t think everyone with Crohn’s disease should now panic and say, ‘I’m destined to have Alzheimer’s.’ It’s not that.”

He wants the information to remind people — whether they have coeliac disease, ulcerative colitis or Crohn’s — that “I really need to make sure my disease is controlled, not only for my gastrointestinal symptoms but for the rest of my body”. It’s when these conditions are uncontrolled, he stresses, that “you are increasing the risk of damaging your gut, hence increasing inflammation, and all the data shows that if you have gut inflammation the chances of increasing brain inflammation are higher”.

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Be particularly vigilant in midlife

During perimenopause, hormone shifts don’t just affect the reproductive system, Nandi says, but also “the gut, the immune system and the brain”. There’s a group of gut microbes called the oestrobolome that influence how oestrogen is metabolised and recycled. “As oestrogen and progesterone fluctuate and decline, microbiome diversity can shift and that may contribute to symptoms like bloating, brain fog, mood changes and inflammation-related joint pain,” he says. Plus, “oestrogen is also helpful in maintaining the gut wall integrity and that also starts to suffer, so you have the perfect storm for these symptoms to happen but also to be more susceptible to gut inflammation.” He advises being “vigilant” about managing sleep, diet and stress, doing “all the things that will decrease inflammation in your body”.

Sleep on your side, and other lifestyle tweaks

Movement is nearly as critical as diet. Nandi’s favourite exercises include walking, cycling and yoga, which can speed up gastrointestinal motility, which slows as we age. Faster-moving stools mean less contact time between pathogens and the GI barrier, which Nandi says can help to reduce the risk of IBS, for example. His other “pillars” of health are “purposeful living, community and spirituality”. “I want you to have great emotional relationships,” he says. “If you’re in a toxic relationship, believe it or not, that affects your gut microbiome and your gut health.”

And prioritise sleep: “Please get six hours, preferably eight.” Studies suggest that sleeping on your side can improve glymphatic drainage — removal of waste and toxins from the brain — and research published in the Journal of Neuroscience suggests this could reduce the risk of Alzheimer’s or Parkinson’s. Managing ongoing stress is also essential: Nandi says that “having unopposed cortisol is very damaging to the gut”. He adds: “Everybody’s looking for the edge — ‘how do I get in an ice bath at five o’clock in the morning?’ — everyone wants the hack. And I tell everyone, ‘The hack is, have great gut health.’”

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Extracted from Heal Your Gut, Save Your Brain by Dr Partha Nandi

Eating vegetables — especially leafy greens — can help the microbiome thrive

CLAUDIA TOTIR/GETTY IMAGES

When it comes to Alzheimer’s disease and helping the microbiome thrive, I tend to recommend the Mediterranean diet. I encourage patients to begin by making it a point to eat:

• Beans
• Fibre-rich foods or a supplement like psyllium husks
• Fruits
• Legumes
• Nuts and seeds
• Oily fish, in moderation
• Olives and olive oil
• Probiotic and prebiotic foods like yoghurt and banana
• Some spices, such as ginger and turmeric
• Vegetables, especially leafy greens

Simultaneously, I encourage them to avoid:

• Alcohol
• Foods with excessive amounts of sugar or salt
• Hydrogenated palm or coconut oils
• Pre-made desserts
• Processed foods

Along with this, depending on the patient’s palate, I recommend they add in other anti-inflammatory foods, especially:

• Avocados
• Organic berries, cherries and grapes
• Broccoli
• Fermented foods
• Green tea
• Mushrooms
• And, of course, turmeric

Supplements

Transforming our diet seldom happens overnight so as patients are making the transition into an anti-inflammatory diet, over-the-counter supplements can be helpful in altering the microbiome in the gut, especially:

• Probiotics like Lactobacillus, which has been shown to improve cognitive function
• The postbiotic butyrate, which decreases inflammation
• Gamma-aminobutyric acid (gaba), which can reduce anxiety and depression associated with Alzheimer’s by modulating dysfunction in the gut-brain axis
• Vitamin D

Probiotics

Pre and probiotics are essential to enhancing and maintaining the microbiome. Diets rich in pre and probiotics (found naturally in fermented foods such as pickles and sauerkraut, leading to decreased intestinal permeability and inflammation) can bring immediate and dramatic improvements in gut discomfort and prevent further damage to the brain. How does this connect to Alzheimer’s in particular? Due to the increased health of the gut, there is decreased inflammation and thus decreased factors that can cause inflammation throughout the body. If eating fermented foods is not an option, I recommend both pre and probiotic supplements.

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Butyrate

Studies are finding that the effects of the compound sodium butyrate can improve the pathological status of Alzheimer’s disease. Butyrate does this by regulating gene expression in the brain, where it has several beneficial effects on neurodegenerative disorders. Butyrate can be produced in the gut by eating copious amounts of dietary fibre. It is also present in butter and parmesan cheese. However, the healthiest and most efficient way to introduce sodium butyrate to the gut is by regularly eating beans and legumes. If eating a bean-rich high-fibre diet proves to be difficult, butyrate supplements are readily available.

Gamma-aminobutyric acid (Gaba)

Gaba is a neurotransmitter in our brain that slows down or blocks specific signals in the central nervous system and is known to produce a calming effect. It can be found in some fermented foods, including miso and tempeh, as well as black and green tea, brown rice, soybeans, mushrooms, sweet potatoes, sprouted grains and cruciferous vegetables. It hasn’t been conclusively determined how effective gaba supplements are at permeating the blood-brain barrier so as always food is the first choice. However, since early trials on mice have shown some promise and gaba may help to relieve the anxiety and confusion related to Alzheimer’s as well, it is a supplement I consider giving under the appropriate circumstances.

Vitamin D

Vitamin D is key to all-around health, especially gut health. Note that poor gut health can be an indicator of inflammatory bowel disease, among others. We get vitamin D from fattier foods, oily fish, and egg yolks as well as fortified beverages and sun exposure, so it’s a supplement I frequently recommend, especially because the variables of food and time outdoors in sunny weather can be hard to control. When it comes to Alzheimer’s disease prevention and treatment, vitamin D is crucial. Not only is it widely accepted that vitamin D decreases inflammation, but a deficiency has already been linked to the onset and progression of many neurological diseases, including Alzheimer’s.

Extracted from Heal Your Gut, Save Your Brain by Dr Partha Nandi (Octopus, £18.99). To order a copy go to timesbookshop.co.uk. Free UK standard P&P on orders over £25. Special discount available for Times+ members