Eating for Your Nervous System

How can what we eat impact our nervous system?
25 March 2021
Presented by Katie Haylor
Production by Katie Haylor.


A pyramidal neurone in the human cerebral cortex


We all know that vegetables and fruits are good for us - high in fibre, lots of vitamins. But what good do they actually do the brain? How does this work? Can food actually prevent neurological issues? Well that’s what Katie Haylor wants to find out in this month’s Naked Neuroscience...

In this episode

Brain schematic

01:04 - Why can smells bring memories rushing back?

We breathe in some of the latest neuroscience research...

Why can smells bring memories rushing back?
Duncan Astle, Cambridge University; Helen Keyes, ARU

A sense of rhythm is, it turns out, critical in the brain. And oscillations provide the beat for brain cells to coordinate their activity around, so they are activated at the right time and in the right sequence. And the paper cognitive neuroscientist Duncan Astle's looked at this month is about how our genes control the rhythms with which brain cells communicate with each other...

Duncan - So let's imagine that you've got multiple different rhythms going on at once in an orchestra. And it's really, really crucial that there's some sort of common temporal code that organises all of the activity. And your brain is kind of similar. So imagine you've got different bits of brain, different brain cells in different locations that are communicating with each other and they're going at different rhythms. So if you, if you were to recall from any single cell, you get what's called spiking activity. That's the action potentials, the firing of the neuron. But if you record from little groups of neurons together, you soon find that their activity patterns rise and fall together like waves. And they produce these kinds of oscillations. And the oscillations are an important way of different groups of neurons, different groups of brain cells, communicating with each other.

Katie - That's beautiful. It kind of sounds like we're all innately musical, whether we've got rhythm or not! We're biologically rhythmic!

Duncan - Yeah. The brain is musical inherently in the way it works, I think.

Katie - What kind of science did they do to try and look into this idea of oscillations?

Duncan - It's really hard to measure oscillations in the human brain. Usually we have to measure them from outside the skull and then infer from where they're coming from. But in this study, they identified 16 humans who were about to undergo surgery to remove a part of their brain that's producing epileptic seizure activity. And in the days leading up to the surgery, what they do is they remove the skull and then they lay electrodes directly onto the brain surface, directly onto the cortex around the area that they think might be producing the seizures. And that's so they can monitor the activity and decide which parts of the brain that they should remove.

And in these days leading up to the surgery, the scientists are then able to record directly from the cortex. And in this case, they had the subjects perform a very simple word, learning task, a memory task. So that's how they recorded these neural oscillations.

Duncan - What they were able to do is look at oscillations at different frequencies. And then find across their 16 subjects, which oscillations and in which locations - so from which electrodes they'd placed on the brain - were significantly associated with people's memory performance. And then after the surgery, they're able to take the cortex they'd been recording from and run what's called an RNA transcriptomic analysis. Which is where you essentially find out which genes are highly expressed in that bit of the brain. So what they've got there is two types of data. They've got the electrical recordings recorded whilst the person was awake leading up to their surgery. And then fresh from the surgery, they've got the actual bits of brain themselves that have been removed that they could then identify which genes are highly expressed and where within that bit of cortex.

Duncan - What you can then do is explore which genes seem to be significantly predictive of the oscillation patterns that are predicting memories. So what is it about the gene expression that's significantly associated with the memory-related activity from the brain? And they're able to explore how those two types of data were associated with each other.

Katie - What kind of conclusions can you come to then about different gene expression and I don't know, quality of memory or kind of aspects of memory?

Duncan - So they found that there are about 300 genes that were significantly correlated with memory related oscillations in the bits of brains that they had removed in these subjects. And what they can then do is explore, "What do those genes do in the brain, what's their function?" And that's done using something called a gene enrichment analysis. And so what you're testing is whether these genes are scattered randomly through people's genomes, or whether they're grouped around particular types of biological process. And what they found is these 300 genes are not randomly scattered at all. Instead they're very tightly clustered around different aspects of synaptic function. So synapsis are the little gaps, the neurochemical gaps between brain cells.

And they found that these 300 genes controlled different things to do with people's synapses. So for example, how different types of ion or neurotransmitters are released into the synapse. What they were able to show is that actually these genes are implicated in a whole host of neurodevelopmental disorders. So autism, ADHD, schizophrenia, difficulties in mental health like major depression disorder. What they think they've uncovered isn't really something specific to memory, but a general principle about how synapses are a regulated by our genes and how those different patterns are associated with the oscillations that those brain cells produce.

Katie - 300 genes! That sounds like an awful lot of stuff to investigate. Is it a case in future of narrowing down a bit more over what particular genes do? Or is it more an overall kind of mechanism that is interesting?

Duncan - Yeah, but those 300 genes don't act in isolation. So they really group around five or six different processes. About 50 of them will be to do with how particular neurotransmitters are released into the synapse. So that's one process that variability in say 50 or 60 genes will be associated with. So even though it might sound like a lot of genes, that's actually not that many underlying biological processes.

Katie - How does this gene association fit in with what scientists already understand about -well, I was going to say the mysterious world of memory, but it sounds like there's a lot of other wider contexts that you're talking about.

Duncan - So the really, really exciting thing here is being able to link the gene expression with something to do with people's neurophysiology. So we've known for a long time that you can take people's genomes and see if that predicts whether they have ADHD or if they have schizophrenia, how well they do at school, all sorts of things. But the question is why? Genes don't code for how well you do at school. They code for proteins in your brain. And the answer here is that one possibility is that they code for different processes that control your synapses. And that is how they have their impact on brain activity and thus those longer term outcomes.

Katie - How do you think this needs to be taken forward? Because it's a relatively small group of people that they were looking at.

Duncan - Yeah I agree it's really interesting. Also lots of caveats, as you say it's just 16 people, they all have temporal lobe epilepsy. But one really interesting thing to do is you can take brain cells and grow them in a dish. One thing you could do is by growing brain cells in a dish in what's called a multi-electrode array, you could actually explore the formations of synapses themselves. And of course you can alter the genes in a causal way in that context. And so you'd be able to then take these 300 and start testing, experimentally, the impact that they have on oscillating activity or spiking activity of the neurons in the dish. So there are all sorts of ways that you can take this forward, now we've got some hypotheses about what these 300 genes are doing and why they're important.


Do you ever come across a smell that - when you encounter it - you’re transported back in time to a particular event, or place, or experience? Perceptual psychologist Helen Keyes explained that it’s long been wondered whether the particularly strong link between smell and memory is down to a stronger connection between the part of the brain that processes smell called the olfactory cortex and the hippocampus - the so-called seat of memory in the brain. But the paper Helen’s been looking at is - she says - the first study that’s actually directly looked at the strength of this connection, in comparison to the other senses’ connection to the hippocampus. Here’s Helen...

Helen - This paper used fMRI to look at 25 healthy participants and it did a whole brain analysis. And it looked at the olfactory (so your smell), the somatosensory (your touch), your visual and your auditory systems in the brain. And for each of those systems, the fMRIs looked at the functional connectivity between the hippocampus and those areas. So in other words, when one of those sensory areas of the brain is activated, is the hippocampus also activated at the same time? And they found that the connectivity, so that activation at the same time between the hippocampus and the olfactory cortex, was much stronger and significantly stronger than any other connection with the hippocampus.

The authors followed this up using intracranial EEG. And this is really interesting. This is where there's some surgically implanted electrodes in people's brains. So they just looked at eight participants here who had surgically implanted electrodes, because they also had epilepsy. But the authors took advantage of this. And they looked specifically at what's happening in terms of timing. So they looked at the auditory cortex and the hippocampus, and they also looked at the olfactory cortex and the hippocampus. And they found this significant phase locking. So in other words, and if you're looking at the timing of when something is happening, when an area is activated, that's the phase locking if these two areas are activated at the same time together. And again, they found significant phase locking between the olfactory cortex and hippocampus, but not so significant locking between the auditory cortex and the hippocampus. Again, suggesting that really strong, direct link between the olfactory cortex and the hippocampus where we form our memories.

Katie - In these experiments, was there any stimulus being applied?

Helen - So in each of these experiments, it was resting state. So participants were just breathing normally, not particularly having any one of their senses stimulated. And it's interesting to us that we can observe, even in resting state, this really strong connection or activation at the same time between these brain areas.

In our evolutionary past, at some stage at some mammals, including humans, developed a neocortex or cortex. So this part of our brain that was distinct from this base primal animal brain. So our hippocampus sits in our real base primal part of our brain, but the rest of our brain, our cortex, when that evolved many of our other senses, so sight and hearing and touch rerouted to those newer parts of the brain, the cortex, that allowed us a species to engage in real cognitive flexibility and abstract representation. So this was a real leap forward for us, for humans. But smell didn't follow the other senses. It stayed deeply rooted in this primal animal brain, right beside the hippocampus.

Katie - That's so interesting. Is this a well-recognised evolutionary path, or is this something that the scientists of this, the authors of this paper are kind of theorising about? Do we know if this is the case?

Helen - We know that the olfactory cortex is located right beside the hippocampus. So we've known there's this integration, this almost physical integration, they're very close to each other. But what this paper has shown is that the other areas, the other senses, haven't got this real direct connection or this activity that's as in sync with the hippocampus as the olfactory cortex. So it could be a possibility - before this study we didn't know if these are the senses, so for example, sight. That could have had a really strong connection with the hippocampus, just via an association cortex via another part of the brain. But this really shows that actually, no, we can directly see that there's a much stronger functional link between the olfactory cortex and the hippocampus compared to any other sense.

Katie - This strong functional link - do you think there's any potential of things working in the other direction? If someone loses their sense of smell, would that have any impact on the way they remember things?

Helen - I think this is a really interesting question and it's going to become more and more important. So there's lots of research done on people who lose their sense of smell. And that research nearly always shows that a loss of a sense of smell can be linked with depression and in general, a poorer quality of life. So we already know that losing your sense of smell gives you, you know, less pleasurable experiences. You don't experience food in the same way, for example. But there is a suggestion perhaps that if your sense of smell is so linked with formation of memories, you're also going to be losing out on that lovely connection on that reminiscence or that ease that you feel often when you get that flood of memory that you associate with a smell. So it's very much understudied at the moment, but will potentially become more and more studied as we're looking at the effects of long COVID for example, with people losing their sense of smell. And what this might mean for them to lose that connection between smell and memory.

Katie - But what you're not saying is that if one loses one's sense of smell, one isn't going to be able to make memories in the same way.

Helen - Oh, absolutely not. It wouldn't be necessary to have a sense of smell to make memories in any way. It's just that they're so connected that those memories and those smells tend to be more integrated. That's all it is.

a photo of some blueberries

Do flavonoids really benefit the brain?
Katie Barfoot, Reading University

What so-called “superfoods” tend to have in common is a high concentration of flavonoids, Katie Barfoot from Reading University told Eva Higginbotham....

Katie - There are a multitude of foods that are good for your brain in terms of brain development, cognition, so your cognitive abilities, and your mood as well. And my specific research looks into flavonoids and whether they are good for the brain or not. Flavonoids are compounds that are found naturally in high levels in foods such as fruit and veg, teas, chocolate, red wine. Flavonoids have actually been found to exert positive effects on our brains, specifically in areas such as memory and also in executive function domains as well. So abilities like planning, working memory, and the ability to kind of self-regulate, organise as well. So they seem to be really beneficial taken in the short term and in the long-term as well.

And the reasons behind this we think are because of mechanisms related to blood flow. We know flavonoids can improve cardiovascular function. So they actually dilate blood vessels, which in turn decreases blood pressure. We know that this is the case specifically after consuming things like cocoa, orange juice, green tea, cranberry, blueberry - that are high in flavonoids. And we think this improved cardiovascular function can actually extend to the brain and increase blood flow to specific regions of the brain that's involved in kind of cognitive function or mood as well.

Eva - What sort of experiments can you do to test whether or not flavonoids or other things might be good for the brain?

Katie - There are two kinds of methods nutritional science uses to look at this question. The first is where we look at epidemiological data - the frequency in the patterns between variables across a population. So this often includes a large number of participants. We find that those who consume a high amount of flavonoids seem to have the most protection from cognitive decline. So in terms of older adults, they have a natural decline in memory as they get older. And we find that flavonoids seem to protect against that decline. Epidemiological data is more focused on the correlation, so the kind of relationships and the links between variables, rather than more cause and effect. We can't control for specific dosages or lifestyle factors in this type of data collection. And we do control for those things in intervention trials. This is mostly what our lab at Reading focuses on running.

You recruit a set of participants. So usually these are from a similar background and a similar age with similar health status. Split the group in two, and you assign one of them the intervention that you want to give them, and you assign the other group a placebo as closely matched to the intervention as possible, but it does not contain any flavonoids. We can then compare across the groups and across time to see if there are any differences before and after consumption of the flavonoid foods.

Eva - What do you find in those studies?

Katie - In cognitive trials, we tend to look at acute and chronic relationships. So the acute period is in the one to six hour post consumption. The chronic literature looks more at what is happening after daily supplementation of a flavonoid. So eating that chocolate bar every day for 30 days, for example. So what we find in the chronic literature - improvements in memory. Specifically in older populations, we see a prevention of memory decline, kind of maintenance of memory in a flavonoid group in comparison to a placebo group. We also see improvements in executive function as well. Acutely, we do see improvements in psychomotor performance, improved visual-spatial ability, improved kind of reaction times. And we also see improvements in working memory as well. And improved episodic memory as well, so remembering certain events or certain kind of points in time.

Eva - The chronic study sounds like my kind of study - eat a chocolate bar every day for 30 days. Thank you very much! How do you untangle the stuff that's in the chocolate bar and the flavonoid? So a chocolate bar of course contains a lot of sugar. Could you not just give people a flavonoid pill or is there something about it being food that's important?

Katie - Yeah. Now this is really interesting. This is something that the field is kind of investigating, you know, as an ongoing thing, really. We do match the intervention and the placebo food, you know, as much as we can. So for example, you're saying about sugar there. Yes. We know sugar affects the body. Sugar does affect the brain as well. So could it be the sugar? The fact that we have the same chocolate bar in the placebo group minus those flavonoids is a nice control. So we can say that it can't be the sugar if we're seeing an increase in the flavonoid group, it must be those flavonoids. Because that's the only thing that's different between the two groups.

Eva - So apart from improving cognition and memory, are there any other effects that flavonoids could be having?

Katie - The field has kind of moved towards investigating the effect of flavonoids on mood. And this is a relatively new area and there has been some primary research that has shown effects. So some research that I conducted with Sundus Khalid, we found that after a blueberry intervention children and also young adults showed improvements in their positive mood. So kind of how they felt on a scale of positive and negative mood items. And we've seen that also as well in recent unpublished data that I've conducted looking at mood in a sample of postnatal mothers as well. My kind of research prerogative is to now look at relationships between mood and flavonoids in populations that are potentially at risk of mood disorders.

Eva - Could you look directly at the brain to try and figure out what the cause and effect is?

Katie - There's quite a few studies scanning the brain using MRI, and also using functional MRI as well which is where you kind of look at the brain in real time to see what it's doing in response to you performing a task for example. Some studies do suggest that there is increased activation in areas associated with the tasks that the participants are performing. But actually the waters are a little bit muddy here in terms of whether those increases in brain activation are actually linked to increased behavioural outcomes as well. So in the studies that have been done on this, we see activation of certain brain regions without emergence of behavioural effects. So it may just be that these increases in activation may just be reflecting cognitive effort, increased concentration to actually perform the task, without actually being better at the task. So the research has still got a way to go in terms of trying to figure out what this dissociation between the two actually means.

Eva - It sounds like it's a really complicated field to untangle the emotional response we might have when we eat something we like versus the stuff that's actually in the food, versus maybe if you're a new mum, having time to sit down and actually enjoy something and having that momentary break and how that might affect your mood. What can we really conclude at this stage?

Katie - There is a lot of research out there that suggests flavonoids are beneficial for the brain in terms of they improve cognitive function or they prevent cognitive decline in older adults. You know, the emerging research on mood at the moment suggests that they may play a part in maintaining positive mood or improving positive mood in certain populations. And we can say that quite confidently from the trials that have been conducted over the last 20 or so years. So the key message in terms of flavonoids is to try and include them in your diet where you can really. And the data suggests that a higher level of flavonoid consumption in your diet across your lifetime will see you have better memory performance and less kind of cognitive complaints as you get older.

Eva - There are some things that are in high flavonoid foods though, like red wine, you said, or tea has caffeine or chocolate has sugar, that might have other effects that we're not such big fans of. Is there a reason that we can't just make a flavonoid pill?

Katie - The research to date suggests that potentially it's down to interactions in the whole food rather than the flavonoid specifically that may be kind of exerting these beneficial effects. So I know there has been some research that has looked at say, you know, a whole blueberry versus the specific flavonoid extract found in blueberries called anthocyanins. And we don't find the same effects. So it may be that actually it's the flavonoids within the other constituents of the food - so such as fibre and vitamins - interacting within our body that may produce those beneficial effects. And that is something that needs to be investigated further in the field.

photo of a man smelling some pasta

Dietary decisions and neurological conditions
Rebecca McManamon, dietician

There are many ways that a dietician might be support someone with a neurological condition. There are the complex neurological pathways involved in coordinating chewing and swallowing, and texture alterations that can be made to make ingestion easier and safer if someone is finding the mechanics of eating difficult due to a nervous system problem. There are the muscles involved in picking up food, dealing with changes to senses of taste and smell, there are the psychological factors around food, recognising hunger and remembering to eat, as well as weight management in some cases. Katie Haylor spoke to Rebecca McManamon  - a neurological specialist dietician and formerly policy officer for the Neurosciences Group of the British Dietetic Association...

Rebecca - For example progressive neurological conditions, things like motor neuron disease, tend to happen later in life, but they can affect people in their twenties, thirties, forties. Regretfully, there isn't a medical cure or definitive treatment for those conditions. So the aims of our treatment are slightly different. It's around supporting their quality of life and what's important to them. So it's a different kind of science. It's the science of marrying goals - what's important to them, talking about the medical impact of what can be quite invasive treatments like having a feeding tube placed. And that can then be further complicated by, for example, if their lung capacity has already been impaired by the motor neuron disease, they may have to have their tube inserted in a radiological way, rather than having a camera or an endoscope down their throat.

So there's so many different factors we need to think about. For some people, food is an incredibly important part of their lives and it's something that is shared with their friends and with their family. But for others, it may be less important. They may be quite happy to receive all of their nutrition in an artificial way so that they can go and spend more time outdoors or spend more time with their family doing other activities. So it's a very, very personal type of treatment. But we're not necessarily treating to cure a condition, but rather to improve their quality of life. But that can very well mean preventing infections, preventing pressure ulcers that can occur if somebody is not able to ingest all the nutrition they need.

So it's quite different to maybe how we may treat someone who acquires a brain injury, perhaps in childhood or in adolescence. Their brain is still developing, at the same time as there having been an injury. So it's quite complicated. There's a lot more potential for them to rehabilitate as much as possible. And again, their nutrition makes a difference. Should they gain too much weight, that could be a barrier to their physical health improving. Should they not grow, should they not be reaching the milestones we expect them to meet, that could be problematic for their future. And then nutrition is quite key there. The type of their overall diet, for example, a Mediterranean diet that has lots of fruits and vegetables that has very little processed meat, that may contain some amounts of oily fish that provide omega 3 for example. That kind of a dietary pattern, whole grain foods, again, rather than processed foods, may very well help with the recovery. But also thinking about long-term prevention because regretfully there can be further injury in the future. So someone who sustains a brain injury is at increased risk of other neurological conditions, like a brain injury related dementia in the future.

Katie - It's really interesting you mentioned the Mediterranean diet because generally, as much as you can generalise with nutrition, a Mediterranean diet is probably a good idea for most people, regardless of whether you have a neurological condition or not. Is that right?

Rebecca - That's fair to say. There's a lot of research that this kind of pattern of eating is beneficial for heart health, for depression, so it can help with so many aspects of one's health. And I guess it's just thinking that where you have sustained a condition where it may benefit you further. So there could be an inflammatory process that's there where you've sustained a neurological injury and that therefore has an impact that you would perhaps get more benefit from it than someone without any medical condition. But it's a good pattern of eating for many people.

But I guess it also leads on to thinking about our gut and the bacteria that live within our gut. And there's a huge amount of research that's going on globally around the gut microbiome. So the community that is living within our guts. And that feeding that community so that perhaps the more beneficial bacteria thrive, which may include some of those aspects of the Mediterranean diet, but not exclusively that, but particularly a lot of those elements. The diversity of what we eat impacting the diversity of our gut bacteria could impact our neurological pathways and that communication between our gut and our brain. There's some interesting research going on here in the UK around Parkinson's Disease. So it's really fascinating.

a photo of someone's legs, wearing jeans and trainers

Vitamin deficiency and the PNS
Rhys Roberts, Addenbrooke's Hospital and Cambridge University

Rhys Roberts is a consultant neurologist at Addenbrooke's hospital in Cambridge and also a researcher on the peripheral nervous system. Katie Haylor asked Rhys how important diet is to peripheral nervous system health...

Rhys - My main interest is in the inherited forms of peripheral nerve diseases. So these are chronic conditions that are usually due to mutations in a number of genes of which now there are over a hundred. But I also see people who present usually later on in life with what we call acquired peripheral nerve problems, or sometimes called neuropathies - again, there are lots of different causes for that.

Katie - Is nutrition a particularly relevant factor when you're thinking about peripheral nervous system damage? Be it inherited or acquired.

Rhys - Nutrition is a very important factor to consider when approaching someone who presents with a peripheral neuropathy. It's been known for centuries that sailors, for example, who were coming back from the far East, eating only a rice-based diet would develop weakness and sensory change in their legs. And it wasn't until the early 20th century where deficiency in vitamin B1, also known as thiamine, was found to be the cause. And this led to the further discovery of a number of other vitamins, all of which have their distinct effect if they're lacking in the diet and can have an effect on the nervous system, but particularly the peripheral nervous system, causing a neuropathy. So this is a key thing that we explore and measure in anyone presenting with weakness and sensory change or numbness in the legs and arms.

Katie - So it sounds like that's a lack of an ideal diet, for instance in the case of the sailors you were mentioning. But what about if you've inherited a peripheral nervous system issue?

Rhys - There are a small number of inherited forms of neuropathy which are due to the lack of the ability to process or use particular vitamins. And that can present with imbalance, neuropathy and particularly thinking of vitamin E, which can mimic a condition called cerebellar ataxia and neuropathy, which is an imbalance where there's a problem with a part of the brain that's involved in the coordination of your limbs. And there are also deficiencies in the way of processing other vitamins as well, which can mimic being deficient of this in your diet.

Katie - It's interesting you made that distinction because it's one thing to be lacking a particular nutrient in your diet, but it's quite another to not be able to use it in the body in the way that you need to.

Rhys - That's right. Often you need to appreciate that. And sometimes you need to bypass where the so-called block is in the mechanism of processing these vitamins, in order to actually treat and reverse the symptoms and signs.

Katie - So where is this absorption happening, then?

Rhys - The absorption of the vitamins occurs in the gastrointestinal tract and there are distinct areas and parts of the intestine that appear to be responsible for the absorption of these vitamins in conjunction with chemicals that are secreted and produced by the stomach and the pancreas.

Katie - Does that then suggest that if you have an issue in your gastrointestinal system, that could lead to a problem with absorbing these vitamins?

Rhys - That's right. Yes. When we first discovered the importance of nutrition and vitamins in a healthy nervous system, as I say, usually in the context of malnutrition or very restricted diets. We have become much more aware that if there are problems in the absorption of these vitamins - usually acquired so these are things that come on in life - that can present with symptoms of a neuropathy. One of the increasingly recognised situations where we see this very commonly now is in the context of bariatric surgery. Very effective interventions, such as surgery, that help with weight loss. And in fact can reverse conditions such as type two diabetes and obesity. We see that these forms of surgery, which often reconnect various parts of the gastrointestinal tract can impair the absorption of particular vitamins.

Katie - How can you mitigate against those ill effects, if someone's having bariatric surgery?

Rhys - It's an increasingly recognised problem as the number of interventions are increased. There are some estimates that around about 16% per year of people undergoing these treatments can develop neurological complications. And most of these is due to not absorbing enough of the required vitamins to keep a healthy nervous system. So increased recognition is key, uh, including getting specialist dieticians measuring these vitamins and elements in your blood and supplementing accordingly.

Katie - Is diet and nutrition an important part of the conversation you would tend to have with your patients who you were looking after, who might have a peripheral nervous system issue?

Rhys - It is. Certainly those who are deficient, and in the clinic most commonly we will see people with vitamin B12 deficiency, which is a relatively common as a cause. Eating a balanced diet clearly is a very important step for both neurological health and also general wellbeing. We do see in the neurology clinic, certain conditions which makes eating very difficult. For example, the motor neuron diseases often cause difficulties for people with their speech, but also with their swallowing, which means they can't eat a normal diet safely and need different texture of foods. They also need to maintain their calorific value in smaller amounts. So this needs expert dietetic input. Additionally, if the swallow is deemed so unsafe in that food tends to, instead of going down the oesophagus, will go into the lungs causing a pneumonia, we can offer insertion of a tube directly into the stomach where we can add food which is balanced and supplemented directly into the stomach. Meaning the person doesn't have to eat but can maintain the required vitamins and minerals and elements that you need for healthy living.

Katie - Is there evidence linking particular dietary habits to protection against peripheral nervous system issues? Because you've mentioned some [dietary] vulnerabilities, and I'm wondering if there's an upside to this?

Rhys - In terms of evidence, it's difficult to support specialist diets other than eating a well balanced diet containing everything that's recommended in recommended amounts. What we've begun to do certainly in the motor neuron diseases is to work in different centres across the UK to study the nutritional intake in people living with these conditions, looking at different ways of focusing, calculating calorific and nutritional need, as opposed to the standard care with a dietician, and seeing if one is more beneficial than the other.

Katie - It sounds like what you're saying is a generally healthy diet is going to be good for your nervous system. And that at the moment there isn't a thoroughly evidence-based kind of pro nervous system diet.

Rhys - That's right. And there isn't any solid evidence that we can turn to that would support any particular diet over the other, which has a role in everyday management of people with neurological diseases.

Katie - Do you have any sort of general nutritional advice above and beyond what we've just talked about that you think might be worth mentioning?

Rhys - So in general, my approach to the people that I see is to support and suggest a well balanced diet, supplemented if needed and if clinically indicated. But I would always be cautious regarding following particular diets that purport to cure or magically reverse a chronic neurological condition. Firstly, because of the lack of clear evidence. And secondly, some of the supplements can prove very costly. So my advice is to take a general approach, a common sense approach, but to make sure that you're ticking the boxes of vitamins.


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