Why do we have body odour?

Why do we have body odour? Can weeds be useful? Could marine animals learn not to eat plastic in the ocean? How does your body warm up when you're swimming in cold water? Why does my dog twitch to a particular sound? If an aeroplane followed the path of a laser beam, would it end up in space? Is time just an illusion? Plus, the science behind a possible insulin pill. Chris Smith joins Eusebius McKaiser to answer your science questions...

Eusebius - Now, our science story this morning is a really really fascinating one, particularly for people who are scared of needles and stuff. Scientists, apparently, have been producing insulin that possibly could be available in pill form...?

Chris - Yes. This is a very exciting breakthrough. For many years we've managed diabetes, where people don't have enough insulin - either they can't make any, or their body doesn't have sufficient insulin for their needs - by injecting it. And the reason you have to inject insulin is it is a protein, and this means that if you were to swallow this chemical then your digestive juices in your stomach and small intestine would break it down before any was able to be absorbed, and that means your blood sugar wouldn't be affected and you need insulin to control blood sugar. So what researchers at Harvard University have done, and published this week in the journal PNAS, and this is Samir Mitragotri, who is the lead author on this work. They have managed to find a way of embedding insulin into what we call an "ionic liquid," and the ionic liquid is made by taking two common chemicals. One is called choline and one's called geranic acid, and when you bring these chemicals together they form a cage, which they literally call it CAGE for choline and geranic acid, around the insulin and it does several things. One, it protects the insulin by stabilizing the protein against the effects of stomach acid. Two, it can burrow through the mucus that lines the intestine and would normally stop the insulin being able to be absorbed. And three, it can prise open these junctions that hold the cells of the intestinal wall together so that the insulin molecule can slip through. And when they administer this to rats, they can show that the blood sugar drops in the same way it would if the rats were injected with insulin but the effect is longer lasting and much more physiological, more natural because the insulin goes in via the intestine rather than from the skin. And so they have high hopes for being able to extrapolate this to what will go on in human. Now, obviously, it's very early days, and it needs safety trials, and needs to be proven that you can do this in a way that's safe for the person's blood sugar, but also is not going to have other untoward effects. But this is really exciting because for years, decades diabetics have had to inject themselves and this carries all kinds of problems. This might be one way that you could turn this into a disease managed by a pill rather than an injection.

Eusebius - Fascinating. Ronald, good morning to you and welcome to the show. What is your question for the Naked Scientist.

Ronald - Good day Eusebius. Good day Chris. I've got aquestion in terms of let's say for argument's sake you set up a laser beam and you ensure that this beam is absolutely level, and then you fly a plane alongside this beam, let's say for 1000 kilometres. Taking in consideration that the surface of the Earth is curved, would that mean then that you would assume the plane would ascend exponentially? That is my question.

Chris - Well, if you were to fire a laser beam in a straight line, then the light doesn't have any mass so the light is not going to be affected, I mean in an appreciable way, by Earth's gravity in the same way that your aeroplane is. But if the aeroplane were to follow the line of the laser beam it would also go in a straight line. It wouldn't go exponentially. I think that an exponential thing is a curve. It would go in a straight line from the Earth's surface out into space.

Ronald - That's actually what I was asking is. So in other words what I'm saying is is that if you fly level and not following the curvature of the Earth you would actually start to ascend?

Chris - Yes, you absolutely would. The thing is that a plane when it's flying, of course, will follow a curve. It won't fly in a straight line and go into space forever for all kinds of reasons of physics. But if you were to fly in a straight line following your laser beam, a laser beam fired from the Earth's surface, for all intents and purposes, would go in a straight line out from the Earth away into space.

Eusebius - Thank you Ronald. Thank you so much for calling. Bafana, good morning.

Bafana - Good morning Eusebius. Good morning Naked Scientists. My question is around weeds. I see that weeds always overtake good crops. So why are the weeds so called and why can't we use [**] as a food source just as they seem to be so in abundance?

Eusebius - Chris?

Chris - Yeah, that's a good question. When I look at my vegetable patch I can see all too clearly how aggressive and invasive the weeds are compared to the things we do want. And the thing is we notice that the weeds are invasive and intrusive because they outgrow the thing we want for the very reason that they do that. It's not that weeds per se have got some special characteristic, it's just that because we like them less than we like the thing we are trying to grow we regard them as more of a nuisance. But there are lots of very productive plants that we do like to eat and grow which are very prolific, and if you put them in the right environment they will grow extremely well. It's just that we tend to notice when things that we don't like outgrow the things that we do like. Scientists are trying to learn from this though and use this to our advantage. Because if you take as an example cereal crops, so wheat and barley and so on, those ancestral cereals did not look like the modern counterparts we have today. The versions of these crops that we have today have been produced by selective breeding. And what we've done is to choose varieties that seem to have a very good yield, they seem to be quite resilient, and they can tolerate weather and drought and so on. They look nothing like their historical counterparts. Now, actually, some of the things that we've bred into the crops are very beneficial like the things I mentioned, but at the same time when you breed for these traits sometimes you can actually lose something. Tomatoes is a good example. The tomatoes we have today are bred to be huge, high productivity, nice looking fruit but they taste rubbish compared to these very much smaller ancestral varieties. People are now realising that actually we've lost something in trying to make something better. So what they're now doing is going back into the history books and back to nature, finding the original ancestral varieties of these things and trying to bring some of the traits that they have back into the modern equivalents. So, in other words, you take the weed equivalent or a distant relative and to try and do selective breeding to bring some of those traits into the modern counterparts so that you can have better disease resistance or faster growth and better flavour more than anything. So weeds can be good too and they're not just a nuisance. There's a good set of genetic diversity in there that we can sometimes tap into.

Eusebius - Laurel, good morning. Welcome to the show.

Laurel - Good morning. Thank you for taking my call. You know how whales and all the mammals are eating plastic and dying from consuming the plastic. I just wondered if there's any chance, what are the chances of mammals eventually learning that it's not nourishing and that it's going to do them harm? They've learnt from other things, you know they don't eat other things like sand in the sea and rocks and shells and things like that. So I just wondered what the chances of them ever learning that plastic isn't good for them?

Eusebius - Thanks Laurel.

Chris - There's a number of aspects to this, and thank you for raising an important issue. The probably most worrying aspect is the amount of plastic in the ocean is huge. It's adding up to millions of tons and millions of particles, and the thing about plastic is it's very long lived. And when plastic pieces rub against each other they don't disappear, they turn into tiny bits of plastic - micro plastics. And these micro plastics have a very big surface area but a very tiny volume and this means they're rubbing up against a lot of water. Because plastic is oil based it can pick up from the water things that much prefer to join up with oil compared with water. So you end up with these tiny micro plastic particles carrying a toxic cargo of all these oil soluble things that are also in the water. Various pollutants, other things such as insecticides, other persistent chemicals which are really not good news. Now those micro plastics then get absorbed by creatures that filter water, so shellfish for example and filter feeders, and they take these plastics in because they're too tiny for them to discriminate against. And they bring them into their body and the toxic cargo clinging to these micro plastics then dissolves in the body of the thing that's eaten the plastic. The thing that's eaten the plastic then poos out the old plastic again but it's now picked up the toxic cargo. Over a long time, those toxic things are going to build up in that filter feeder. But then along comes a fish and eats the filter feeder. Now you've got a fish which has got all of the toxic cargo in the fish. And then along comes a bigger fish and eats the smaller fish and it's got all of the toxic cargo that was in all the small fish it was eating. And in this way these chemicals can accumulate through the food chain. And then along comes your big top predator mammal like an elephant seal or something, and he or she eats a big fish which is full of all of these things that have accumulated up the food chain. So the animal hasn't had to learn to discriminate against plastic or not, it's just going about its business and it's eating things tit would normally eat, but it's having an indirect effect of the plastic brought to bear on it. And this is the big problem that although there are some bits of plastic we can see, there are lots of effects of plastic that we can't. And the lifetime of plastic in the ocean is incredibly long which means we're going to have to live with the legacy of this for a really long time and it's really hard to do something about it, which is why people are campaigning. Let's try and stop it getting any worse now so that at least the problem won't continue to explode. Because if we carry on at the present rate, and we've already got a big problem, we'll have a ginormous problem.

Eusebius - Judy, good morning.

Judy - Hi. Good morning. I want to know when I swim in winter, as I did today. When you're out in the pool it's freezing. Well after 50 metres, you know when your arm comes up out of the water into the air it doesn't get cold. It feels nice and warm. How does your body just get warm so quickly?

Chris - Mine doesn't.

Eusebius - Judy's in the Republic of Hout Bay in Cape Town.

Chris - That's cold water. I don't have this problem. I have a real problem getting into really really really cold water. And in fact we did a program on the Naked Scientist for our Christmas show a few years ago where there is this group of people who go ice swimming in many countries - Russia they do it. In London, there is an open air pond that people break the ice in winter to go swimming, and we sent one of our staff and she did go swimming. And most of the interview consisted of bleep noises actually because she hardly uttered a word that wasn't unbroadcastable.

But the bottom line is that your body is very sensitive to change and your nervous system is programmed to detect change. Because, at the end of the day, when things change that could be a change for the better, but it could be a change for the worst. You need to know when things are changing so you can attend to them. So your nervous system is exquisitely sensitive to something suddenly departing from what it's used to, and then it gets used to the new state of affairs and it signals that change to you. So when you first put your hand in very cold or very hot water, then you're going to have a barrage of sensory information coming to your brain saying Wow, something has changed. And superimposed on that is the whole sensation of is it hot or is it cold and whether or not we find that unpleasant. Now once you get used to something, a number of things happen. One your body goes into defense mode, so it actually replumbs the route the blood is taking through the body withdrawing the circulation from the surface of the skin to cut down the rate of heat loss. You also increase your metabolic rate to generate more heat so that you don't get so cold. And your nervous system adapts to the fact that you are in a cold environment so it doesn't keep on reminding you it's cold because things aren't changing you're now cold, so you have got used to the situation. So I think in this situation you have adapted your nervous system to the ambient temperature of the very cold water and so your body temperature has stopped plummeting because you've directed blood more towards your core than your skin and, therefore, your rate of heat loss has slowed right down. And, under those circumstances, you're able to tolerate it for maybe 10 minutes or so before you might become dangerously cold.

Eusebius - Thanks for that question Judy. Much appreciated. Paul you've been holding on. Thank you for your patience. Get straight into your question.

Paul - Yeah, hi. I've got two Jack Russell - one male one female. The male's a little different as in from a puppy he would watch television, bark at National Geographic etc. But my question now, which I discovered recently, was I've got a cell phone body glove. A heavy duty one so the plastic's quite thick. If I take my fingernail and I strum like a guitar a  littletune, it makes clicking sound, his lower jaw moves instantaneously in exactly the same rhythm as my clicking. Now what's interesting about this is that obviously for the human eye I can't see a time lapse at all. There obviously is one but it's very very small. The other day I did it while he was asleep and his jaw still moves when he's sleep. It actually wakes him up. So you explain to me. I've gone to 20 other dogs and it's the only dog that does this

Chris - Animals are very sensitive sound, and dogs have exquisite sense of hearing. A friend of mine had a budgie that used to dance to Meatloaf she used to play. It was only Meatloaf, right. She could play other things. I don't know what was special about Meatloaf but a Bat Out of Hell II, it really liked. Bat Out of Hell I, it didn't care. And it would Bob its head in time to the bass beat of Bat Out of Hell II from Meatloaf. And we did the experiment, we'd try other things, very similar genres of music didn't have an effect. So the bird, obviously, was exquisitely sensitive to that particular frequency. Dogs do have very good ears and there are connections in the nervous system that elicit reflexes, so when you when you are present a stimulus then you can get a response, and some humans do this. You can you can make a sound or you can have an unexpected thing happen and someone would twitch in response to it. And it's probably because that there is a certain set of connections in the brain that when you present that particular sound stimulus, or it could be a visual stimulus or whatever, it then elicits a certain pattern of nerve activity that, in certain individuals, will result in a certain muscular movement. I suspect that's what's going on that the clicking noise of a set of frequencies to which the dog is sensitive and, at the same time, is eliciting the response in the hearing parts of the brain. There might be some additional connections onto those motor areas that correspond to the dog's face muscles and it's eliciting that twitch, but also it's when it's processing the sound that is then getting aroused and woken up by it.

Eusebius - Was your friend's bird committed to doing Anything for Love?

Chris - It would do anything for love actually. It would do anything for birdseed. There was a very funny comedy actually where they made a song called I Would Do Anything for a Shag. That's another kind of bird. They had a guy dressed up as Meatloaf driving around on a motorbike with a big barbecue, you know a brai on the back of the motorbike and they changed the words I'd Do Anything for Grub. Because they were saying he's a little bit on the large side, of course.

Eusebius - Paul, welcome to the show. What do you want to ask Chris?

Paul - Yeah, It's regarding body odour. And I know the lazy answer would be it's caused by sweat. I have an 8 year old who has a terrible body odour. I've tried a number of things but they're not working. Is there any scientific reason why she has this terrible body odour? I don't know if there is.

Chris - Well, there's a number of reasons why this happens. The reason we do have odour, for the average person, is because when we sweat then the water that's in the sweat feeds bacteria, which are living on the skin surface quite naturally. And those bacteria use the water, the moisture, they use other chemicals and oils which are secreted from apocrine glands which are in the sweaty bits, and dead skin, and other things that they can eat. And they take that banquet and turn it into bacterial burps, which are body odor - whiffy volatile chemicals and, therefore, having a decent wash can help. Using an antiperspirant deodorant can help, because antiperspirants don't just mask smells. Antiperspirant deodorants have various substances in them that form a gel when they get wet and they effectively clog up your sweat glands, so they reduce the amounts of water coming out onto the skin in the sweaty places and that can cut down the dampening effect, but also the growth of the microbes. So hygiene and antiperspirant deodorants can help.

Some people do have a condition which means they produce a lot of sweat. And this can be a nerve situation, and some people can be helped with this by actually activating the part of the nervous system called the "sympathetic nervous system" that drives the production of sweat. In some people it's pathologic; they get very sweaty hands, for example, and it's a real problem for them and this can be sorted out. Now there's a rare condition which is called "trimethylamine urea," and this is where people have a fishy smell and it is because of a metabolic problem. It's not really a problem, but it's that they can't break down certain molecules and those molecules have a fishy smell - this is trimethylamine urea.  And trimethlamines, they end up in your sweat because they can build up to higher levels in the bloodstream and they get filtered out into the sweat, and they do make people have a fishy odour. And these for these poor unfortunate people, through no fault of their own and it's not through bad hygiene, their body just produces these smells. They can end up with a fishy whiff and there's not much we can do about that apart from perhaps change their diet a little bit to reduce the production of these molecules but you make them for your metabolism. And this is rare but it's something that perhaps could be excluded.

Eusebius - Our final question for the morning comes from you, Mena. What is it?

Mena - Hey, good morning. My question is Einstein said that time is just an illusion and that the past, present, and future exist simultaneously. So if I extrapolate that to the universe itself and say that the death of the universe exists simultaneously at this moment, and then the death of time exists simultaneously with this moment. Then I can't get my head around why does anything exist at all if the death of the universe and time itself doesn't exist?

Eusebius - Okay. Thanks Mena. That sounds enormously complicated for our final minutes. Chris?

Chris - Well, if there's no time then why is there a time limit. I'll talk forever!

Eusebius - Touché!

Chris - The programme is already finished. Mena, you know you say you can't get your head around it. I can't get my head around this concept either. The bottom line is that we know that time is ticking. We can put a date on the origin of the universe, and we know how old the universe is - about thirteen point eight billion years. So we know that basically that there is an arrow of time and we know that the universe is growing and inflating. We know that it may have an ultimate death. It may have no end. We just don't know. I don't pretend to understand the physics. I don't think Einstein would have been able to say for sure what was going on because when he came up with all of his theories, he fiddled some of them because he thought he'd got something wrong. In fact he hadnt, he wanted the universe to be static. He didnt want it to be growing and he couldn't reconcile the fact so he put a fiddle in the fudge into his equations. Actually, the universe is growing and now we realize he shouldn't have fudged his equations, you're absolutely right. But we don't really know and we don't understand how a lot of this works, which is why we need physicists. So everyone go to university and study quantum mechanics because this is going to have the answer for us.

Eusebius - Chris, a wonderful segment. Thank you so much and we'll do it again next week.

Chris - I'm looking forward to it. Thanks everyone. Take care. Bye bye.