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Junk food, asthma and eczema; salt; fingerprinting; TGA; amitriptyline

Dr Mark Porter goes on a weekly quest to demystify the health issues that perplex us.

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28 minutes

Programme Transcript - Inside Health

THE ATTACHED TRANSCRIPT WAS TYPED FROM A RECORDING AND NOT COPIED FROM AN ORIGINAL SCRIPT. BECAUSE OF THE RISK OF MISHEARING AND THE DIFFICULTY IN SOME CASES OF IDENTIFYING INDIVIDUAL SPEAKERS, THE BBC CANNOT VOUCH FOR ITS COMPLETE ACCURACY. INSIDE HEALTH TX: 15.01.13 2100-2130 PRESENTER: MARK PORTER PRODUCER: ERIKA WRIGHT Porter In today's programme: What your fingerprints can reveal about the drugs you've taken and why the police are not the only ones hoping to harness the new technology. Old drugs, new tricks - we examine the ascent of amitriptyline from out-of-favour antidepressant, to popular remedy for everything from migraine to back pain. And imagine not being able to remember a thing about what has happened to you so far today - nothing that you have seen, heard or read, where you have been, who you have met, or what you have done? We answer a listener's question about the day she lost through amnesia. But first some research that has been all over the news this week an international study showing a link between junk food and the risk of developing asthma and eczema. The coverage suggests that children who eat junk food more than three times a week are more likely to develop asthma and eczema - but eating just three portions of fruit and veg a week offered some protection. Inside Health's Dr Margaret McCartney has been digging a little deeper - Margaret is that a fair summary? McCartney Yeah no I think it is and I think was - the advantage of this study was it was a really very big study indeed, they looked at almost 800,000 children around the world and the impact of their diet and whether or not they were more likely or less likely to get asthma and eczema. And obviously there's been a big concern about the rates of asthma increasing and people are trying to find out really why that is, what it is about us now that seems to make us more likely to have these disorders compared with 20, 30 years ago. So I think this is very useful work. But it's an association study which means that there was an increased association but it doesn't actually mean there was an increased cause, so we can't really say that junk food causes asthma or eczema, I think that would be a step too far, but I think it's a very interesting association and deserving of further work. Porter When they do these sorts of studies though presumably do they look to try and rule out other confounding factors? McCartney Yeah and I think that's something that scientists would try and do, they would try and reduce the risk of barriers, so things appearing to be differently from what they really are, so obviously there's reasons why children might have more junk food in their diet compared with other children, maybe children that live in more urban areas, for example, might be more likely to have more junk food in their diet or maybe children who are poorer for example. But it's always very difficult to get rid of these biases altogether, so we can never be quite sure I think that they're not there. Porter And does it fit with anything else that we know already? McCartney Well there's lots and lots of evidence already about the importance of fruit and vegetables in diet and they do seem to have protective effect on reducing the risk of asthma and eczema in children and that's been done in lots of different studies in lots of different places in the world, so I think there's already percolating evidence about that. What I think's a bit new or a bit different is the association with junk food. What I find really interesting though about the fruit and vegetables is that it's something quite achievable, so usually we're told five portions of fruit and vegetables a day or you're failing whereas this one said three portions of fruit and vegetables a week was protective, which I think is much more realistic for children who maybe don't like their veggies. Porter That's a tiny consumption isn't it. And what is it about the junk food? McCartney I think we just don't know, to be absolutely honest with you, I think more work needs to be done and certainly there's lots of people with lots of theories as to why junk food might increase your risk of asthma or eczema but I think it's fair to say that we don't really know. Porter Well thank you for now Margaret. Salt is another diet related issue that has been in the headlines recently after Shadow Health Secretary Andy Burnham suggested that legislation could be introduced to reduce levels in processed foods - the source of 80% of our daily intake. The lobbying group Consensus Action on Salt and Health (CASH) estimate that around 20,000 deaths from stroke and heart attack could be prevented every year in the UK if average consumption was reduced to below the six gram limit currently recommended. That's roughly a teaspoon's worth. Current consumption being closer to 10 grams a day or a teaspoon and a half. Salt tends to increase blood pressure, which in turn prematurely ages the lining of arteries increasing the risk of an early stroke or heart attack. But while there is good evidence that it raises blood pressure, how sure are we that reducing intake will save thousands of lives. And how helpful is cutting out salt at home, if most of what we eat is hidden inside processed foods? I'm joined by Dr Kamran Abbasi, editor of the Journal of the Royal Society of Medicine and by Graham MacGregor, who's Professor of Cardiovascular Medicine at Barts Hospital in London, he's also Director of CASH and one of the driving forces behind moves to reduce salt intake - both at home and via processed foods. He is convinced by the evidence - regards salt as a toxin - and has little time for research that suggests otherwise. MacGregor There have been one or two papers that have come out of [indistinct word] but when you look at the evidence contained in them they really don't come to very much and that is the view of the American Heart Association and I was involved in writing a paper with all the leading experts in the world on this who looked at all of these papers and concluded that the evidence is overwhelming and that we must reduce salt intake. Now I would say that we're in the same battle as we had with cigarettes, they are a lot of parallels. Porter Kamran. Abbasi I think one of the issues in drawing a comparison with smoking is that when it came to changing policy, getting people behind the anti-smoking movement the evidence base was clear, there wasn't much debate except from very vested interests in terms of what needed to be done. I think one of the issues here is that there is a debate and there was an article published just last month in Health Affairs, one of the most respected medical publications in the United States, which described the debate as being at fever pitch. So the debate is there and the debate - the question really is you talked about projections of benefit has benefit from - in terms of reducing death and reducing illness - has that been adequately demonstrated to get the movement behind the salt reduction campaigns that's required? MacGregor Well yes, I mean firstly, going back to the evidence base, I mean the point you're trying to make there's this big debate going on, that isn't true, if you go to the WHO, you go and talk to individual countries they all agree you should reduce salt. The debate is taking place between the Salt Institute, which is the public relations company for the salt, that's spending a large amount of money because salt is very valuable to them and largely the American food industry which of course will suffer a lot if they're forced to reduce salt in their foods. And there's good evidence for that, I'm sure you're aware of the commercial interests of salt - salt is put into food that you wouldn't eat to make it edible, it's often at the concentration of seawater, it binds with polyphosphates in meat products and fish products to gel them, so you can take all the leftover bits of meat, bone, hair and everything, gel it into a sausage with salt, similarly with fish fingers - they're gelled and the essential chemical there is salt, if they took that out they'd have big problems and salt is the major drive to thirst and therefore responsible for soft drink, beer consumption and mineral.... you can't really see the soft drink companies backing any serious salt reduction campaign because we've shown it would result in billions of soft drink sales less a year. So there's huge commercial interest out there and I think you're not looking - it's exactly the same as the tobacco story, there's a big but slightly more convert industry there - the food industry - and particularly backed by the extremes of the Salt Institute. Porter You're being hoodwinked Kamran. Abbasi Well perhaps I am but I mean I'm not hoodwinked by the food industry or have any connection with them but I think that's the heart of the argument, that's the argument that Graham needs to win beyond the advocates of salt reduction in the wider research community. Porter Are we clear in terms of evidence - and this is a question to both you - that reducing salt actually has a directly beneficial effect on the incidence of heart attack and stroke, in other words it reduces your risk or are we extrapolating that - we know it has an effect on blood pressure and therefore it's likely to have an effect on stroke and heart attack - do we have direct evidence? MacGregor Well we have evidence for both, we have very good evidence that reducing salt will lower blood pressure in populations both in normals and hypertensers and reducing salt in children when blood pressure first starts also lowers blood pressure, very good studies. There is also experience in two countries, one in Japan that had a salt reduction campaign in the '60s where salt was very high in the northern islands and they were very successful in reducing salt intake at a time when Japan was rapidly becoming Westernised - smoking, gaining weight, more fat, less fruit and vegetables, less exercise - and yet stroke and blood pressure levels fell dramatically in Japan during the time they were reducing salt intake. And the same experience in Finland that had a big reduction in salt from around 16 grams a day to 9 with huge reductions in blood pressure and stroke mortality. Porter But how do we know that that was due to salt reduction? MacGregor Well the problem is with... Porter I mean heart rates have been falling here - heart attacks. MacGregor Just got to be careful about - I'm not saying we shouldn't be careful because in any dietary there are no dietary outcome trials properly conducted and what you'd need to do is take newborn babies randomised one route to a high, the other to a low salt group, follow them up for the rest of their life, of course it would be unethical study, impossible to do, you can't restrict salt in the community particularly in Western countries, all the salt's in the food. Porter Kamran, we're never going to have gold standard evidence but there's a weight of evidence that suggests that this relationship's important, do you accept that? Abbasi I think there's a weight of evidence - and just to be clear - I'm not against salt reduction, I think there is a weight of evidence that supports - from my understanding of it - that supports a link between salt reduction and reduction in blood pressure. There's limited evidence in terms of ultimate health outcomes, the outcomes as clinicians we're interested in, and again... Porter Do our patients live longer and healthier? Abbasi Exactly, patients living longer, not dying early, not getting cardiovascular disease and we do require more data if a robust public health campaign is to be built around it. Porter Is there a problem in having a society that eats much less salt, I mean what's the downside of this advice, if, Graham, if it's not as effective as Graham would think? Abbasi I think when it comes to the public I think the public perception is that salt - if I add salt to my food this is bad for me and... Porter All my children... increasingly happening. Abbasi Yes exactly and I think what is clear is that if there has to be a line of attack it does have to be industry. And the question I would ask that if the link is so clear, so robust, then why in this country are we pursuing a voluntary code instead of introducing regulation, which would force companies to reduce the level of salt in food because that's the logical extension of your argument. Porter Graham, can I just take this down a slightly track, does it matter for a healthy child or adult with normal blood pressure how much salt that they have? MacGregor Oh absolutely yes. Porter I mean assuming the blood pressure remains within the normal range. MacGregor Well it doesn't, as you know blood pressure goes up throughout life, starting early in childhood and the rate of that rise in blood pressure in epidemiological studies have been shown relates to the salt intake and there's a lot of other evidence for that. And of course age 30 30% of the population have high blood pressure, at 50 50% and at 80 80%, so if you haven't got high blood pressure now you're going to have it later mate and that is largely due - not entirely due - to our very high and unnecessary salt intake. Porter And there's good data to support the fact that by consuming salt as a child or a young healthy adult that you'll bring forward the time when you might develop blood pressure, you're convinced about that? MacGregor Absolutely yeah. Porter Kamran. Abbasi We're not talking about salt that people add in cooking, we're talking about... MacGregor No you're absolutely right... Abbasi That's the point that we need to be very clear about. MacGregor Eighty per cent, on average, of our salt comes courtesy of the food industry and all the processed foods - bread, bacon - and actually people in general add very little salt compared to the amount they get from the food industry or when they eat out at fast food restaurants. So the strategy in the UK, which has pioneered this, is to get the food industry to slowly reduce the amount of salt in bread. Now you probably haven't mentioned - noticed Kamran that actually the salt content of bread has fallen in the last seven years by 25% and all the ready prepared meals have come down by 40%, bacon has come down and no one's noticed and that is a brilliant public health policy because we're reduced salt without actually having any effect on what people buy, much as we would love people to change their diet it's very difficult to do, whereas if you change it without them realising and do it slowly it's brilliant and that's been copied now all over the world. Porter And what would you say to a parent who's got young children at the moment? MacGregor Well I think there's multiple things to say. Well first of all they should not eat salt and there's no need to eat salt and that will prevent them getting high blood pressure later in life, remember blood pressure's the single biggest cause of death and disability in the world. Porter Prevent them - that's a - if they don't eat salt - if they don't eat excessive amounts of salt. MacGregor They will not develop high blood pressure in my view. Porter That's a pretty sweeping statement. MacGregor Yeah it is but I think it's correct. Porter Kamran given what you've been looking at, I mean how would you advise people? Abbasi Well personally I don't put salt in my food but I think Graham doesn't help his argument by ignoring that people disagree with him, I don't necessarily agree with those people... Porter That wouldn't be the first time that that's happened in medicine. Abbasi But there is a debate around this issue and I think what I would say is I think you need to be careful with your salt intake and keep it to a minimum but not be alarmed that you're using salt in everyday cooking. Porter Dr Kamran Abbasi and Professor Graham MacGregor, thank you both very much. And you will find some useful links on the subject if you go to and head for the Inside Health page. Now from the table salt in our diets, to some very different salts found in our sweat, and a new device that can tell what drugs you've been taking by analysing your fingerprint. Something likely to prove very useful when treating confused or unconscious patients in casualty. David Russell is Professor of Chemistry at the University of East Anglia. Russell It's a handheld device the size of a regular landline telephone. The device works very simply - we're measuring the drugs that are excreted in the sweat of a person's fingerprint, it's just deposited onto the surface, so if you can imagine fingerprints that are put on the TV screens or glass windowpanes, it's exactly the same as that, it's the sweat/water that is deposited on a surface. And we're able to pick out the drugs that have been excreted by the patient just naturally. Porter And how long after someone's taken a drug would you still be able to pick traces up using this technique? Russell That is dependent on the drugs that people take, some drugs stay in the body for a long period of time - weeks - others are excreted very quickly. And think of this as a scenario: A patient comes in to an accident and emergency unit, the clinician has no idea what that patient is suffering from. Actuality - A&E Creday My name is Dr Andreas Creday, I'm a locum consultant in emergency medicine, we're standing here in the accident and emergency department of Leicester Royal Infirmary. Porter Andreas, I would imagine that you get quite a few people come in here who may be on medicines or maybe have taken medicines that you need to know about, at the moment how does it work, how do you find out what people have taken? Creday Well if they're conscious then we obviously ask them what they've taken, how much they've taken. The problem really arises for us if they are unconscious and cannot communicate to us or don't want to talk to us. What happens at that stage is that we would either treat them empirically for a suspected overdose based... Porter So you guess effectively - educated guess? Creday We really have a guess and look at what they look like clinically. The alternative is to take blood tests or urine tests from them and send those off for evaluation, another problem with that is that the results of those - preliminary results - take about 24 hours and complementary results take about five days to get back. So in an accident and emergency department that is no help to us whatsoever. Porter And some of these people might be quite ill? Creday Very ill - unconscious, not breathing, have a low pressure - and we don't really know what we're treating at that stage, so we throw everything at them. Porter And by knowing exactly what they've taken presumably that allows you to tailor the treatment accordingly? Creday Yes, so there are specific antidotes for different drugs and if we know what they've taken specifically then we can treat that with the correct drugs instead of throwing all sorts of different antidotes. Russell The sweat of a fingerprint is 98% water but the other 2% consists of salts, so if you lick your fingers you know they're salty, drugs are excreted in the sweat that we can pick up in the minute quantities that are deposited in a fingerprint. So we're dealing with very low quantities of sweat but the concentrations of the drugs are there enough so that we are able to pick these up. So just if you think of the breathalyser for alcohol detection we're able to pick up similarly for drugs in the fingerprint, it just provides the same ratio as what is present in the bloodstream. Creday If somebody ingests something with a very - they inhale it or they inject into themselves the body would break that down into different compounds, different products and your body then gets rid of that either through your urine or your sweat or through your liver. Being in sweat that would then allow us to analyse those bi-products and we know which bi-products come from different drugs, so by knowing which bi-products are in the sweat we know which drugs they've taken. Porter And the results are available almost immediately? Creday Within minutes. Porter And does the machine have a set number of things that it scans for or would you do one drug at a time? Creday So it would scan for different drugs simultaneously, there are four drugs at the moment that the technology is scanning for, so that would be opioids, so the bi-product of heroin and methadone; it would look for bi-products of cocaine and cannabis. Porter And at the moment you have four drugs in the system but presumably the technology could be extended to include many, many more? Creday Two different drugs, so one of the more common ones that we have problems with especially in the elderly populations is benzodiazepines, which are sleeping tablets like valium that a lot of patients are on, they may occasionally take too many of their sleeping tablets... Porter Well either accidentally or on purpose I suppose is possible. Creday And if somebody - an elderly patient - comes in unconscious we don't really again know what it is and if we can take the benzodiazepine or valium products out of the equation that'll be really helpful for us. Porter Dr Andreas Creday - and if you would like more information on the device the team at Leicester is helping to develop then visit the Inside Health page of Don't forget if you would like us to try and shed some light on a health issue that is confusing you then please e-mail me via This e-mail from an anonymous listener caught our eye: "I suffered from transient global amnesia 11 months ago. I behaved normally to those around me - I was evidently chatting and driving a car - but at midday I complained to a friend that my head felt empty. They took me to hospital and by late afternoon I was back to normal but I can't remember a thing about the whole day. It is just like it was erased from my memory. I had lots of tests - including a brain scan - but nothing was found. I am 70 and otherwise well. It's all very strange and confusing. What causes this type of amnesia and is it common?" A question I put to memory expert Professor Roy Jones, Director of The Research Institute for the Care of Older People in Bath. Jones That story is absolutely typical, it's a transient problem, the person, unlike someone say who is confused or has had an epileptic fit or those sorts of things, will actually be acting totally normally - they might drive, they might play the piano - they will act totally normally but they aren't remembering what's going on and they will often ask the same question repeatedly because they're a little bit concerned about things but they're behaving normally. And then at the end of the episode they'll have absolutely no recollection of it whatsoever. Porter And what do we think's going on? I mean our listener had a - stayed in overnight, was obviously checked top to toe, had a CT scan and all sorts of other investigations - everything came up clear. Jones Yes and again that's fairly typical. The age range usually is people between 40 and 80, it tends to last about one to eight hours, maximum of 24 hours. There are a number of theories about it, one of them it does seem maybe to relate to venous congestion within the brain using - after something called the valsalva manoeuvre, when people hold their breath, and that may occur, for example, when you're straining at a stool, during sexual intercourse, if you're lifting something heavy. There's also been reports of people going into cold water, for example, something that may generate it. People have tried to do a certain amount of imaging during some of the episodes and it does look as if there is something going on within the hippocampus and the related areas and the hippocampus is the area in the brain that is important in memory. And it seems very likely that it's something to do with either venous congestion sometimes or possibly narrowing of blood vessels or ischemia. Porter So this would be a change in blood flow and that would have a direct effect presumably on brain chemistry and the functioning of the brain? Jones Yes and there is a slight overlap - some people have a history of migraine so there may be some of those elements within it. Porter What's the future hold - is this something that tends to recur in people? Jones No characteristically it doesn't recur or if it does recur it's fairly uncommon. If it does recur then it does make you think about other things. For example, some types of epilepsy can sometimes present in a slightly similar way. So it is important to try and check it out. And the other thing that's important about the episode is that someone has witnessed it because obviously the person themselves can't really describe it, so getting a good history, for example, if they had any weakness or any signs of slurred speech or anything like that it would make you think it might be a transient ischemic attack, a mini-stroke. So you're looking really to find nothing significant other than the loss of memory for that period and behaving pretty normally during the period. Porter Professor Roy Jones talking to me from out studio in Bath. And while transient global amnesia may be rare, since I mentioned that we were covering it last week, we have had four listeners get in touch with similar stories. You can e-mail us via or send a Tweet to @bbcradio4 including the hashtag insidehealth. One common source of confusion among patients at my practice is the drug amitriptyline - and the way doctors now seem to use it as a treatment for such a diverse range of problems. Originally launched in the sixties as an antidepressant, amitriptyline fell out of favour with the advent of newer alternatives like Prozac. But it has staged a major comeback in recent years as a painkiller - particularly for neuropathic or nerve pain. Leaving many of my patients wondering why I am treating their pain with an antidepressant. GP Margaret McCartney joined consultant anaesthetist and pain specialist Dr Mick Serpell at the Pain Less exhibition at the Science Museum to learn more. Serpell Neuropathic pain is damage to the nervous system somewhere along the line so it might be somewhere like a peripheral nerve, the nerve going into the arm being crushed or cut or it could be central nerve pain such as the spinal cord or even a brain injury. Lots of different causes whether it's trauma or infection, like shingles, or whether it's metabolic like diabetes - all these different sources can damage the nerve and cause nerve pain. McCartney And things like sciatica when people have got nerve compression in their back with low back pain and they get pain down their leg, a kind of burning pain, that kind of thing is something I see with patients with sometimes. Serpell That's right yeah, sciatica's another example of a central neuropathic pain. And the interesting thing about all these different types of neuropathic pain is that the patients words that they use to describe these pains are very similar, words like burning, tingling, sharp, jagging, pins and needles, things like that are very commonly used. So these are red flags that this is likely to be neuropathic pain. McCartney So I've come here to talk about the drug amitriptyline which I understand you use very commonly in your pain clinics? Serpell Yes it's a very common drug which is classed as an antidepressant but we use it for pain relief which it works for in people who aren't depressed. McCartney And that's a funny situation to be in because the package information about the drug inside the packet that patients get home with them it's all about the use of amitriptyline as an antidepressant and doesn't say anything about it as a pain medication. Serpell That's right, a lot of them have had trouble for many years trying to get the message that they are in severe pain across to healthcare workers or even their family and their employers and so they often feel misbelieved because it's a subjective symptom, it's something that is very difficult to show, most pains are experienced internally. So patients have this big problem of being believed and if someone meets them for the first time and prescribes amitriptyline, which is labelled as an antidepressant, and they read about this in the literature in the packet then they immediately think they're not being taken seriously. So it's fundamental to explain why an antidepressant is being used for a pain. McCartney Because it's not actually being used as an antidepressant? Serpell That's right. Historically amitriptyline was licensed for depression and over the years has been found to be effective for nerve pain but because the drug is an old drug and off patent, less than a pound for one month's treatment, no company has gone to the expense and bother of getting a licence for its use in pain relief. You could take the example of aspirin, which serves many functions, it's an anti-fever drug, it's an anti-arthritic drug, an anti-inflammatory drug, an anti-blood clotting drug - does lots of different roles but it's not called all these different names, whereas amitriptyline unfortunately is labelled an antidepressant and that's what everybody thinks it's being prescribed for. McCartney So basically the drug amitriptyline works as a pain drug in people who are not depressed, so it's not being used as an antidepressant, it's being used as a drug for pain - how come, what's happening in the brain when we take it? Serpell Well pain mechanisms rely on signals and certain chemicals play a role in that and the two big chemicals are nortriptyline and serotonin and it just so happens these chemicals can be involved in depression but a lot of antidepressants although they modulate those systems don't work for pain, whereas amitriptyline and a few other select small number of antidepressants actually do modify the balance in the correct way that allows pain relief to come about. McCartney It's almost that you're choosing the pain in the brain rather than actually in the bit of tissue in the leg or the ankle or arm or whatever that's affected. Serpell That's right, so what these drugs is do is actually enforce the body's own pain suppression and they go straight to the chemicals that are responsible for suppressing pain. So they basically help the body's own pain suppression pathway to get stepped to start putting the brake on pain. But because it is an old drug it does have a lot of side effects. McCartney And the kind of side effects that you could expect to get with amitriptyline? Serpell Well just because it does work on the nerves the main side effects are on the central nervous system which is the brain so that includes drowsiness, tiredness, cloudy thinking, sedation - these are the main ones that affect the brain. McCartney And does it matter that it's described as an antidepressant on the packaging rather than as a painkiller? Serpell I think as long as the patient is aware it shouldn't make any difference. There is the stigma, obviously, of being prescribed antidepressants but if the patient is aware of why they're getting the medication and they can explain to their colleagues or family then the misunderstanding should be cleared. Porter Dr Mick Serpell talking to Margaret McCartney at the Science Museum. Just time to tell you about next week's programme when, among other things, we will be answering a listener's query about dry mouth and having a closer look at sunbeds. We are not convinced by recent claims that sunbeds don't increase the risk of serious forms of skin cancer, or that Manchester United has installed one solely to boost players vitamin D levels. Join us next week to find out if our scepticism is justified. ENDS