DR MICHAEL MOSLEY: Why looking after your gut could protect your brain from dementia

Now at the age of 64, top of my anxiety list, healthwise, is a fear of developing dementia. 

My dad, who died when he was just 74, was showing signs of confusion and memory loss before he passed away and I have, down the years, heard many heartbreaking stories of people struggling to cope with relatives affected by dementia.

Fortunately, there are plenty of scientifically proven things you can do to reduce your risk (more on that in a moment). And now research points to a surprising new place where you might want to start: by improving your gut health.

There are at least 100 trillion bacteria, viruses and fungi living in our guts, with a mix of ‘good’ and ‘bad’ microbes. Very recently scientists have begun to appreciate that these microbes not only affect your gut, but your brain as well.

For example, Parkinson’s disease occurs when critical nerve cells in a part of the brain called the substantia nigra start to die off. This in turn leads to a reduction in levels of dopamine, a brain chemical that helps boost mood, but that also plays a vital role in helping us move.

The big question is, what causes the initial damage to the brain cells? For a long time we didn’t know, but recent research is firmly pointing at our colony of gut microbes (called the microbiome). It’s known that well before anyone shows signs of Parkinson’s, they tend to develop gut disorders, such as constipation.

A study last year in the journal Nature found that not only do people with Parkinson’s have a different mix of microbes from those who don’t have it, but specific species seemed to help, or hinder, progression of the disease.

Broadly speaking, the ones that were beneficial helped reduce chronic inflammation, while the ones that did harm promoted it.

And it seems that the same thing may be happening in the brains of people with Alzheimer’s, the most common form of dementia.

A couple of studies, discussed earlier this month at Alzheimer’s Research UK’s conference, provide fresh evidence of a link between the gut and the brain.

In the first study, researchers from King’s College London analysed blood and poo samples from 68 patients who had Alzheimer’s and 68 people who didn’t. As in the Parkinson’s study, the researchers found that people with Alzheimer’s had a different mix of gut bacteria and signs of greater inflammation.

This doesn’t prove it’s the microbes in the gut causing brain problems — it could be that people with Alzheimer’s eat a very different diet, or that having Alzheimer’s alters your gut microbiome, rather than the other way round.

But it provides more evidence that those microbes could be playing a significant part in how the disease progresses.

The people who most closely followed a Mediterranean-style diet had healthier-looking brains and did better on the memory tests, —— they also had lower levels of amyloid and tau proteins in the cerebrospinal fluid; these are thought to play an important role in the development of Alzheimer’s and other forms of dementia

A second study, from University College Cork in Ireland, found much more direct evidence of a link. In this study they transplanted poo samples from people with and without Alzheimer’s into rats. The rats infected with gut bacteria from people with Alzheimer’s later performed worse in memory tests, grew fewer nerve cells in areas of the brain associated with memory and had more inflammation in their brains than the other group of rats.

As Professor Yvonne Nolan, a neuroscientist who led the research, explained, while it’s proving difficult to directly tackle Alzheimer’s processes in the brain, ‘the gut potentially represents an alternative target that may be easier to influence with drugs or diet changes’.

So how can you use this information to reduce your own risk?

Well, as Professor Nolan points out, the quickest and easiest way to change the balance of the microbes in your gut is to change your diet.

And we already have abundant evidence that a Mediterranean-style diet, rich in olive oil, nuts, oily fish, fruit, vegetables and legumes, is not only good for your microbiome but also for your brain.

In a study published last year in the journal Neurology, researchers in Germany put a group of middle-aged people, some of whom were at higher risk of developing dementia, through a battery of blood and brain tests (even checking samples of their cerebrospinal fluid, the fluid that bathes the brain).

The people who most closely followed a Mediterranean-style diet had healthier-looking brains and did better on the memory tests, —— they also had lower levels of amyloid and tau proteins in the cerebrospinal fluid; these are thought to play an important role in the development of Alzheimer’s and other forms of dementia.

Apart from diet, researchers from University College London recently identified ten other ways to reduce dementia risk, which they say could delay or even prevent nearly half of all cases.

The list includes some things which are difficult to change (avoiding head injury and being better educated); some which are relatively obvious (more exercise, giving up smoking, drinking within the guidelines, treating high blood pressure and depression, not getting type 2 diabetes, keeping to a healthy weight) — and a few that are more surprising.

These include maintaining lots of strong, social contacts, which is good for your brain; getting your hearing tested (poor hearing means you’re less likely to engage with others); and avoiding exposure to air pollution.

I’m doing what I can to keep my brain, and my gut, in good shape. And my wife Clare, who may have to look after me if I do develop dementia, says she plans to be more diligent about ensuring I do my exercises and don’t sneak any sugary treats into the house.

The price of my misspent youth 

Tooth enamel is as hard as steel but it’s also vulnerable to acid attack.

Sadly, when I look in the mirror, I see quite a lot of teeth that have been filled and drilled — the result of consuming a lot of sweets and fizzy drinks in my adolescence. Bacteria, coating your teeth, turns the sugar into acid, which then steadily erodes the enamel.

So, I read with great interest that researchers in China had developed a new, artificial form of enamel which they say has the hardness, strength, versatility and toughness of the real thing.

And they have achieved this by copying the structure of real enamel. What makes enamel into the hardest substance produced by your body is that it is composed of tightly packed calcium and phosphate mineral crystals.

According to the Mohs scale of mineral hardness, tooth enamel scores 5, which puts it on a par with steel, though well behind diamond, which ranks 10.

I am hoping that by the time I next have to have one of my crumbling teeth replaced with an implant, this new artificial enamel will be available.

In the meantime I am diligently flossing and brushing my teeth — and wishing I had looked after them better when I was young.

A lily will help your lungs

Nitrogen dioxide is a common air pollutant that can damage your respiratory tract and increase your vulnerability to respiratory infections.

Long-term exposure to high levels of nitrogen dioxide can also cause chronic lung disease. It is a gas that is commonly produced by traffic and construction work, but you can also get high levels indoors, from poorly ventilated domestic gas ovens.

But there is a simple way to significantly improve air quality, and that’s by adding houseplants.

That was the conclusion of a new study by the University of Birmingham, in partnership with the Royal Horticultural Society. They took a number of houseplants, including three particularly popular in the UK — peace lily (Spathiphyllum wallisii), corn plant (Dracaena fragrans) and fern arum (Zamioculcas zamiifolia, pictured) — and put them into a test chamber containing the sort of levels of nitrogen dioxide you’d find in an office close to a busy road.

Within an hour these lovely plants had managed to remove half the nitrogen dioxide in the chamber. Based on this, the scientists estimate that if you are working in a small, poorly ventilated office all you need to significantly improve air quality would be five plants.