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Reality bites: Does eating bananas repel mosquitoes?

Posted on January 20, 2010 by Wendy

It was a lovely, balmy night. A couple of my friends were sitting outside enjoying a meal as the buttery sun began to set. Suddenly, I could feel something moving on my arm. I knew what it was straight away, and without a second thought WACK! With great satisfaction I looked at my arm: a squished insect and a smudge of blood, the little bug-ger got me already. I whined with disgust, mosquitoes always get me. My mate offered a friendly suggestion: “You should eat bananas, it repels mosquitoes.” Really? I wondered. Does it?

While I am more than happy to chug down bananas any day of the week, I’d rather not be under some impression that I’ll be saved from the wrath of the mossy, if it just ain’t true. After checking the facts about this myth – it seems that reality bites.

Meet the mossy

Our mini rival weighs about two milligrams. And while they are simply annoying little critters to the Western World, mosquitoes are responsible for millions of deaths worldwide. Their bite can carry lethal diseases, such as malaria, dengue, and West Nile encephalitis. Consequently, mosquitoes have been dubbed the world’s most dangerous animal.

Only female mosquitoes need blood because they use it to feed their eggs (mosquitoes’ mainly get their nutrients from plant nectar). As a result, it’s only female mosquitoes that are attracted to humans. Human attraction is also specific to different mosquito species, which is why in some areas of the world you might be a mossies favourite meal, but in other regions they glide right past you – ready to bite a neighbouring cow or donkey.

Why are mosquitoes attracted to humans?

It’s all in the nose. Mosquitoes use smell to find mates, food and blood meals. There are human-specific molecules on your body that give off a particular smell, and mossies can recognise them. These molecules waft through the air until they reach a mosquito, and bind to special receptors on its antennae. When this happens it begins a chemical change in the mosquito, activating their nervous system and alerting them to your presence. Now the mosquito knows who you are, and where you are. Any minute she’ll be on your skin, feeding on your arm. So what are these human specific molecules?

There’s a lot. Carbon dioxide is on the list. IT’s one of the most universally recognized mosquito attractants and can draw in mosquitoes from up to 35 meters. Some compounds in sweat also attract mosquitoes to humans, as do lactic acid, body heat, and odours produced by skin bacteria.

What repels mosquitoes?

Since it’s smell that attracts mosquitoes to human, it’s also smells that repel mossies. Mosquito repellents that can be bought at the supermarket all work by interfere, directly or indirectly, with the mosquitoes’ sense of smell. Some repellents bind to those smelling receptors, which means they are blocked and can’t detect other human specific smells (kind of like a finger up your nose to stop you smelling). Other repellents are just stinky, so the mosquitoes avoid the smell. The most effective, and popular repellent, DEET, might do both; scientists are still debating this one. But onto another debate – do bananas repel mossies?

The Banana Myth

Word on the streets is that eating bananas repels mosquitoes. But the myth isn’t consistent. Others say eating bananas attract mosquitoes. And others still say that it’s not bananas but vitamin B12, which is jam-packed into this fruit, that is making the mossies come our way.

According to the American Mosquito Control Association (a scientific/educational, not-for-profit service), it doesn’t matter what the myth is – they are all wrong. Vitamin B12 has no impact on mosquito biting, and nor does eating bananas. Dr Cameron Webb, an entomologist at Westmead Hospital’s Institute of Clinical Pathology and Medical Research agrees. He says eating vitamin B also won’t help the mossies get off your back.

But there is some new science giving this myth a leg to stand on. A study published in Nature magazine in 2009 from the University of California, noted that mosquitoes have very similar smelling receptors to the Drosophilia fly. And studies in the past have found that the drosophilia avoids smells from a certain chemical found in bananas (3-octanol). This chemical is also found in grapes and strawberries. So, it’s possible that mossies might also be repelled by this chemical as well.

There’s more that needs to be studied. It’s not enough that the smell of bananas repels some mosquitoes – that smell has to waft out of our skin, or breath, or bum, when we eat it.

According to the American Mosquito Control Association, laboratory studies asking people to eat bananas have been conducted, and no repellent action has been found. The only problem is: I couldn’t find these studies! (Can you?)

Okay, so it looks like eating bananas probably won’t affect how attracted mosquitoes are to you. It’s your breath and sweat that is mainly alerting them to your presence. But there is a possibility that some chemicals in food will make a difference. In the meantime, while the experts keep searching for the conclusion, I’d pop on some good old fashion repellent. Just to make sure those mossie bites don’t make you go bananas.

More mosquito matters!

- Why are some people more attractive to mosquitoes than others?

According to Webb, it’s not that people are more attractive to mosquitoes; it’s that some people have a stronger reaction to mosquito bites than others. The itchy red lump from a bite is our immune system reacting to the mosquito’s saliva, and some people have a smaller immune response to the mosquito salivas.

- What’s the best repellent?

Recently investigators at New England Journal of Medicine compared 16 mosquito repellents, including (DEET), soybean oil, and citronella. They tested how effective they were by timing when the first bite took place – after people applied the repellents. Soybean oil was effective for 94.6 minutes. But DEET was best. Only after 112 minutes (almost two hours) was a person bitten when wearing a DEET-based repellent of 6.65% concentration.

Posted in Disease: bugs and grubs | 4 Comments

Burping: putting it down to a science

Posted on January 12, 2010 by Wendy

It was social suicide: “I can’t burp!” yelped little Suzie at the College party. There was howling and nasty finger pointing, as the peeps at the shin-dig filled their glasses with beer and downed it in record time. Burping and belching erupted in a gas filled night of fun and debauchery. Poor little Suzie, was something wrong with her schooling that meant she couldn’t belch? Or was there something wrong with everyone else that was making gas rise from their bellies and out of their mouths?

Why do we burp?

Burping or belching, scientifically called eructation, happens when swallowed air is released from your throat or stomach through your mouth. As the stomach expands to let food in, it relaxes the lower part of your oesophagus and this allows air to be sucked into your stomach. Once the lower part of your oesophagus relaxes it triggers your upper oesophagus to relax and expand too. This means that air gets vacuumed up the throat, and out of your mouth in a big ol’ BURRP!

So, there was nothing wrong with the people at the party, because swallowing air is perfectly normal when you eat, and burping is a normal way to release that gas. In fact, scientists reckon that around 30mL of air is ingested every time we swallow.

Why can’t Suzie burp?

After much scientific searching, I couldn’t find any papers describing people who can’t burp, or explaining why some people can’t do it. Now this is not to say that some people don’t have difficulty burping, it’s probably more the case that not being able to burp isn’t a big enough problem for biologists and medical doctors to spend some hard earned funding trying to solve the conundrum.

From first principles, it seems that if little Suzie can’t burp, a few things could be happening. Perhaps the food and way that Suzie eats means that she doesn’t swallow very much air as she eats. Or maybe her lower or upper oesophagus doesn’t naturally expand to such a great extent to let air in – so it doesn’t vacuum pump a burp out of her mouth.

What if I burp too much?

Funnily enough, the real problem in the scientific burping community related to burping is people who burp too much. Outside of a college frat party, excessive belching can be quite embarrassing. And indeed if you do find yourself in front of the queen with such a condition, you might want to get acquainted with the word: Aerophagia, which literally means to eat air.

Aerophagia describes an array of conditions related to eating air, including excessive belching, abdominal pain, bloating and abdominal distension. According to studies describing the condition, it’s somewhat common – “every gastroenterologist occasionally encounters patients who consult primarily because of excessive belching” says one paper. Aerophagic patients often find themselves frequently belching at times unrelated to meals.

Quite interestingly, the vast majority of these aerophagic belches come from air sucked into the oesophagus and expelled out immediately, before it reaches the stomach. These supragastric belches are different to most burps, which enter the stomach and then get burped out.

What would cause excess belching?

Other gas-related symptoms that form aerophagia, such as bloating and abdominal distension are commonly associated with gastrointestinal disorders, like the irritable bowel syndrome. But since the excessive loud burps of aerophagia come from air that doesn’t reach the stomach, it’s difficult to say whether gastrointestinal disorders are to blame for this condition.

Studies have shown that patients with aerophagia swallow the same amount of air as patients without the condition. This removes excess air in the throat as a possible cause. In fact, even the air bubble size of the gases are the same for aerophagic and non-aerophagic people. This has left scientists rather confused about the condition, and an expert’s best guess at this point is that excess burping is caused by the mind, not the body.

There are a couple of reasons that researchers pinpoint psychological issues as a cause of aerophagia. For one, most patients don’t have the condition forever – in fact the median duration of symptoms is 24 months. Plus, in a large analysis of aerophagic patients there was a high prevalence of anxiety and depression. Repetitive belching has also been spotted in the initial representation of some neuro-psychiatric disorders.

To study if belching was somehow related to the mind rather than the body researchers took 10 patients with excessive belching and distracted them to test if distraction reduced the number of burps the produced. Amazingly – it did! When patients were told that their burping was being measured, the frequency of belching was more than doubled. But during the distraction period, when patients were asked to fill in questionnaires, the belching rate substantially decreased. Why stress and psychology might lead to excessive belching is currently unknown.

So it seems that it’s not little Suzie at that frat party that we should be worried about. Suzie is doing just fine. It’s the stressed, confused Sammy, that hasn’t drunk any beer, and is belching loudly and frequently that is a cause for concern. And to this day, with all of our scientific knowledge, the cause for his excessive burping remains an anomaly.

Posted in You and Your Body | 1 Comment

Anti –oxidants: Are they all they are cracked up to be?

Posted on December 9, 2009 by Wendy

A few moments ago a friendly neighbour told me to eat some antioxidants to get rid of a cold that I’ve had for over a month. Jeesh, it really seems that antioxidants have truly become the be all and end all to health! Not only do these guys fight against cancer and aging, but now, apparently they can also fight viruses and bacteria. I didn’t really know what to say to him. He was just trying to be friendly. But still, I couldn’t help but ask – “Why would antioxidants that protect DNA, help to kill the viral infection that is making me cough?”

I got a blank stare in reply. This was promptly followed by an awkward silence; and a slow retreat. I promptly went to my computer; sat down, and wrote this article. It’s time to explain what the devil anti-oxidants are and why they are not the key to killing my cold.

What are anti-oxidants?

When our stomach breaks up things in the body that we need for energy, like food, it also makes free radicals. They are a kind of by-product of metabolism. Free radicals are very reactive, and they like to bind to anything they can get their hands on. This includes DNA, proteins and fats. Once they bind to these things, especially DNA, they can damage them, which this can lead to cancer. As free radicals are naturally produced in our body we also have a natural defence mechanism to protect against them … anti-oxidants!

While our body naturally makes anti-oxidants, we can also get them from external sources, like fruits and vegetables. Famous anti-oxidants you may have heard of include: vitamin E, vitamin C, selenium, and B-carotene. Less famous anti-oxidants include glutathione. (It’s less famous, because the body naturally produces it, so pharmaceutical companies don’t often sell it to you.)

Both internal and external antioxidants get rid of the dangers of free radicals by attaching to them. This means that the free radical’s hands are full, so they can’t bind and destroy our DNA.

Most of the time there is a nice equilibrium between the free radicals and the anti-oxidants. But disease, smoking, pollutants in the air and radiation can increase the amount of free radicals that our bodies are exposed to, and that’s when trouble can strike. Studies have shown that as some cancers progress, the amount of free radicals in our system increase. This tells us that, in some cancers, there is a very close link to free radicals and cancer.

When it comes to cancer are anti-oxidants all that we dreamed they would be?

Studies using cell cultures (putting cells into a dish and watching the effects) have confirmed that antioxidants have anti-cancer qualities. Plus, more than 250 studies show that the more fruits and vegetables jam-packed with essential antioxidants that we eat, the lower our risk for getting cancer is. But there is some inconsistency. While cancers of the mouth and throat, lung, stomach, colon, and rectum show a pretty consistent reduced risk with high fruit and vegetable consumption, data for breast and prostate cancer, are less consistent.

And, studies also tell us that not all anti-oxidants are created equal. Different anti-oxidants help with different conditions. Selenium and vitamin E reduce the risk of colon and throat cancer. Foods rich in lycopene, such as yellow vegetables, and tomatoes, are linked with reducing the risk of prostate cancer. Garlic and onions, which have high levels of the antioxidant organosulfur, reduce gastrointestinal cancer risk.

Green, but not black tea, has been shown to reduce the risk of breast cancer by 20 percent. Eating foods rich in carotenoids, like carrots and green vegetables, can help reduce breast cancer risk, but don’t do much for reducing lung cancer.

So, they are all we dreamed they would be!?

No. Studies are telling us that antioxidants are not always good. B-carotene, while linked to reducing breast cancer when you consume it as a vegetable, is also linked with increased cancer-related deaths when consumed in supplement form. So how could they be good and bad? Well, we aren’t entirely sure, and that’s because we don’t exactly know what all of the different anti-oxidants do in the body, and why they affect different cancers in different ways.

All we know is that out of a whole bunch of people who ate a whole bunch of B-carotene in vegetables, some had a reduced chance of getting breast cancer, while another study found that when B-carotene was eaten in a supplement, they had an increased risk of dying from cancer.

Some scientists think that when we have a lot of B-carotene it increases free radical production, but at lower levels it is an anti-cancer fighter. Plus, there is a little more confusion because when B-carotene hangs around free radicals that have been made from cigarette smoke we know that B-carotene is cut up into many different unstable products. These products could trigger more free radical production, adding a whole new level of confusion. It seems that anti-oxidants act different around different free radicals and at different quantities. Vitamin A and E have also been shown to act like free radicals at higher doses and under different conditions.

While fruits and vegetables definitely deserve their place at the bottom of the food pyramid, it’s important that we don’t get sucked into the world of bigger is better when it comes to anti-oxidants. 200grams ain’t necessarily better than 1. Nature is pretty clever, and if fruits and vegetables have low quantities of particular anti-oxidants, maybe it’s better they stayed in those quantities.

Can anti-oxidants kill my cold?

And just in case there was confusion, anti-oxidants cannot protect us against colds and the flu. These diseases are caused by viruses or bacteria that get into our bodies, and start making a little home for themselves. Anti-oxidants can’t really bind to these buggers and kill them. In fact it’s quite the opposite. When our body tries to kill viruses and bacteria it will often make special kinds of free radicals that can fight against them.

I guess the war between anti-oxidants and free radicals isn’t one of good and evil. We need to make free radicals to break down energy, and kill bacteria, but we sure don’t need it to damage our DNA. And we need anti-oxidants to control the free radicals, but too much of a good thing can cause damage. Moderation is the key, and nothing is the be all and end all to health. So don’t trust the media, or any friendly neighbours. Trust me.

Posted in Food: finding the proof in the pudding | 2 Comments

Does stress give you dandruff?

Posted on November 8, 2009 by Wendy

When we stress it can feel as if our body is in meltdown – our heart is permanently racing, it’s difficult to sleep, and to make matters worse, when stress has hit its peak, sometimes our head gets itchy and dandruff flakes dance from your scalp to your shoulder. So why is it that when we are stressed we get dandruff? Is it just because we don’t bathe, or wash our hair when we are busy? Or is there something more?

What is dandruff?

Dandruff flakes are dead skin cells on the scalp. Naturally, skin cells die and fall off to make way for new cells, but we usually don’t notice because there aren’t too many of them and they wash out when we wash our hair. It’s only when scalp skin cells die off excessively that we notice. It’s estimated that more than 50 percent of the adult population have had dandruff. So why do the skin cells on our head shed excessively?

The major cause of dandruff is a fungus, called Malassezia fungi that can live on the scalp. Scientists are getting close to understanding precisely why this fungus gives us dandruff, but we are sure we have the right culprit because anti-fungal treatments work best to remove the symptoms of dandruff. Plus, when animals are inoculated with the fungus, they often get dandruff-like symptoms (skin flaking etc.).

Aren’t you gland scientists are working on this issue?

In 2005 scientists from the USA and Korea found an important clue to explain why this fungus causes dandruff. They showed that when a gland in our body, called the Sebaceous Gland, was active, people were more likely to have scalp flaking disorders. The Sebaceous Gland becomes active during puberty, and stays active in our 20s and 30s. It produces stuff called sebum which is found on our scalp, face and back. Sebum maintains the structure of skin, and protects it from bacteria, fungus, and ultraviolet irradiation. Ironically, while sebum is supposed to be protecting our scalp from fungus, it is actually one of Malassezia fungi’s favourite meals.

The fungus is a very fussy eater, and while it loves sebum, which is made up of saturated and unsaturated fatty acids, it only eats the saturated fatty acids. This means our scalp is left with too much unsaturated fatty acids. It’s thought that excess unsaturated fatty acid leaves our skin vulnerable to flaking, and dandruff. However, the dandruff debate isn’t all cleared up (and neither is my dandruff). The Malassezia fungus is found on healthy scalps as well as dandruff sufferers. This tells us other factors must be involved. Could one of these factors be stress?

Does stress increase our risk of dandruff?

Possibly. While studies of general stress are hard to come by (because stress is so subjective), in 2007 a study of 82 patients suffering from depression and anxiety found that 82% had an excessively flaking scalp. When we are stressed, our body makes substances called glucocorticoids which calm us down. Glucocorticoids can change the make-up of the cells on our scalp, possibly leaving us susceptible to Malassezia and the dandruff it causes.

The good news is: while scientists don’t know exactly how stress increases our chances of dandruff, we do know that most dandruff can be cured using anti-fungal shampoos and conditioners. Now if only we had time to wash our hair during stress then all our problems would disappear!

Posted in Getting emotional | 2 Comments

What are butterflies in our stomach?

Posted on October 27, 2009 by Wendy

He’s so gorgeous; you want to ask him out on a date, but you’re having trouble saying the right words. Your stomach is churning and fluttering. You feel a little sick, and you might have had a little diarrhea (of course he doesn’t need to know that). What is happening to you is perfectly normal: you’re nervous, and you’ve got butterflies in your stomach. But that’s hardly a scientific explanation for what is going on. After all, you don’t really have insects fluttering around your belly. Do you?

Stomaching the brain

Of course not! But what you do have is a second brain hiding in the human stomach. This brain houses around 100 billion nerve cells in our digestive tract (which is more than those found in the spinal cord).

While the Central Nervous System is made of your brain and spinal cord, the gut’s brain is called the Enteric Nervous System (ENS). It is found in the tissue that lines the oesophagus, stomach, small intestine and colon. It’s called a system because it is a complex network of neurons, chemicals that help neurons communicate with each other (neurotransmitters) and support cells. All of these ingredients are also found in the brain in our heads. In fact, nearly every substance that helps run and control the brain (in your head) is also found in the gut, including serotonin, dopamine and adrenaline. Plus, like the brain in our heads, the complex circuitry in the ENS allows it to act independently, learn and even remember.

Brainy development

Here is some food for thought (ahem): in foetal development the two nervous systems originally came from the same clump of tissue called the neural crest. When a foetus is developing inside the womb this crest forms very early, and then it splits. One section goes to the head and spine, and becomes the Central Nervous System, and the other section becomes the Enteric Nervous System. These two systems then become connected when a large nerve, called the vagus nerve, develops between them.

Stress head

When the brain (in our heads) is in a stressful situation it releases stress hormones, such as adrenaline, throughout the body. The lining of the stomach (like our brains) has many adrenaline receptors. When adrenaline surges through our body, it is picked up by the receptors in the stomach. This leads to butterflies and cramps. (This also explains why some women get period pain… the hormones are going out of control, and the stomach picks up on it.)

Fear also incites the vagus nerve to ramp up its production of serotonin in the gut. This over-stimulation can cause the gut to digest food faster than usual, leading to diarrhea.

The second brain also explains a lot of common phenomena that happen to us when we are stressed or emotional. When people get “all choked up” with emotion it’s often due to nerves in the oesophagus being highly stimulated, leaving people with difficulty swallowing.

Plus, we now know why drugs such as antidepressants can give people a physical reaction like gaining weight, nausea and cramping. Since similar chemicals and receptors for those chemicals are found in the head and gut, when you make a drug to have an effect on the brain, it’s very likely to affect the gut too.

And finally, ever had a gut reaction that you followed for no rational reason at the time, and only afterward realized it made sense? Well, the Enteric Nervous System has a memory, and can learn, so this bunch of nerves in your stomach is probably the answer for this marvel too.

Of course it might be a little hard to swallow, a brain in your stomach, but why not? We tend to plan our lives around our next meal, and our next coffee break. Perhaps it is time that we gave our stomach’s a little more credit.

Posted in Getting emotional | 4 Comments

Stretching the facts: Should you stretch before playing sport?

Posted on October 14, 2009 by Wendy

It’s often thought that stretching before exercise is a great way to prevent sports injury, and reduce muscle soreness. Some textbooks even suggest that stretching before exercise can improve physical performance. But the science isn’t so sure. In fact, a whole bunch of recent reviews on the topic suggest that stretching right before exercise does nothing to reduce injury and muscle pains, and it might even reduce athletic performance! Sounds like a bit of a stretch, but let’s look at the facts.

Muscles: 101

Skeletal muscles are muscles that attach to the skeleton, and are responsible for moving your body. While it might look like your muscles are making a huge range of movements – they are just doing two things: contracting and relaxing.

A muscle is made of many cells called fibres. These muscle fibres are long cylinders. Inside the muscle fibres are myofibrils, or muscle proteins. Within these proteins are sarcomeres, which are the power engines that actually contract the muscle. When we think about moving a muscle, a signal is sent from the brain to the muscle fibres which fire up the sarcomeres. This contracts the muscle.

When we stretch, we are actually contracting different muscles on the opposite side of the limb. To stretch my hamstring, I am actually contracting my back-leg muscles, called the biceps femoris.

So why did we ever think that stretching could reduce sports injury?

There are two factors linked to sports injuries – muscle stiffness and range of motion, which is related to flexibility.

One popular theory says that stretching the muscles increases the number of sarcomeres in muscles, which lengthens the muscle, and increases flexibility. Since injury is related to range of motion, and stretching increases this, it didn’t seem like too much of a stretch, that stretching reduced injury.

But a paper published this year from Brazil pointed out that there is no definitive evidence that stretching physically lengthens the muscle. And in their study of 45 undergrad students, they found that stretching programs didn’t actually increase muscle length. But they still found that stretching increased flexibility, which they proposed happened for other reasons. So it looks like the science about stretching isn’t so clear.

When scientists aren’t 100% sure about what is happening deep inside things, they look at statistical evidence.

Two large studies, which together used over 2600 army recruits, tested whether stretching reduced their sports-injuries. In the first study one group of trainees stretched their calf muscle twice for 20 seconds on each limb before exercising, while a control group didn’t stretch. In the second, more rigorous, study one group of trainees were asked to stretch six muscle groups in the lower limbs before exercising, while another group didn’t stretch. In 2002 researchers from the University of Sydney carefully combined these results and found that stretching did not reduce injuries in the recruits.

Does improved flexibility reduce muscle injury?

Well, most injuries actually happen in the normal range so having extra flexibility might not help.

On this, research suggests that because stretching increases flexibility beyond what is needed for physical activity, it might actually cause injury because it allows your body to make movements that it shouldn’t.

This might seem ground breaking, but the Australian Institute of Sport has already cottoned on to the new findings, and their policy on stretching gives less emphasis on static-stretching during the warm-up.

What about Muscle soreness?

Surprisingly, just like scientists don’t know precisely what is happening to the muscle when we stretch, they also aren’t so sure about what happens when muscles get sore after playing sports. This is different to the pain we feel during sport, which is caused by a build up of lactic acid.

One theory says that delayed muscle soreness, 24 to 48 hours after exercise, happens due to small injuries in muscle fibres that lead to inflammation, swelling and increased free radicals throughout the body. This inflammatory response excites things called nociceptors, which can transmit information about pain.

Three very recent reviews looking at all the studies worldwide on stretching and muscle soreness concluded that exercise does not prevent muscle soreness. And the most recent of these reviews notes that this isn’t too surprising considering contemporary ideas about what causes muscle soreness don’t have anything to do with the possible effects of stretching.

And what about performance? Can stretching before exercise make me run faster?

This one gets a no as well. In fact 20 studies on the topic found that a stretching session before exercise diminished performance for power workouts, like running and jumping. Considering that stretching increases flexibility, it also changes the tension we need to put on our muscle to get a fast contraction.

So there you have it – when it comes to stretching before exercise the science says – don’t worry about it!

But studies have shown that regular stretching, at a time unrelated to exercise, might improve performance, flexibility and help you relax. Let’s save that for another day. For now, I’m off for a run – and thanks to science – I’m not going to bother stretching.

Posted in Uncategorized | 2 Comments

Will you need glasses after sitting too close to the Computer?

Posted on October 5, 2009 by Wendy

You’ve been looking at the computer all day. You have a slight headache and your eyes are blurring. You look around and have trouble focusing the book shelf, which is only three metres away. Sounds familiar?

You start thinking: This can’t be good for my health, before I know it my 20:20, naturally perfect, vision will decline. I’ll need glasses and children will pick on me and call me “four eyes”.

But, will they?

Fortunately, the answer is no. Children no longer refer to people with glasses as four eyes. Plus, according to the science there is no definitive link between staring closely at a computer screen and short sightedness. So what is happening to your eyes when they go blurry? And is it actually bad for your health?

The long and short of being short sighted

“Short sightedness”, or myopia, is a condition where distant objects appear fuzzy, but objects that are close look clear. When light comes through your eye it first hits the cornea and then the lens. The cornea and lens are curved surfaces that bend the light to make it hit the retina. A person with myopia has a longer eye than usual, or their cornea is too curved. As a result the light bends, but doesn’t hit the retina in the correct spot. This means that you can’t focus on objects that are far away without corrective glasses. (Glasses bend the light so it hits the retina correctly).

Could this happen to me when I stare at the computer?

Probably not. “Near work” is the technical term for visual activities that happen about 40 centimetres (16 inches) from the eye. This includes reading a book, knitting, and staring at a computer screen. Several studies have searched for a link between near work and short sightedness, and they haven’t found one yet.
Scientists reckon that some people are susceptible to developing myopia from near work, but it’s only a small subset of vulnerable people.

What are the risk factors for myopia?

Risk factors that have been spotted are hereditary factors (i.e. if your parents are short sighted), and the amount of time children spend in the sun. A recent Australian study compared two groups of children: both spent the same amount of time watching TV, reading and playing computer games. But the outdoor group spent two hours a day outside, and the other spent only 30 minutes outside. The results? The outside group had much fewer instances of myopia. Aussie researchers thought that the sun might help the eyeball grow and develop during childhood.

If I’m not going short sighted – why are my eyes fuzzy after staring at the computer?

After you’ve been gazing into the eyes of Google many people experience uncomfortable symptoms – like difficulty focusing on objects, and tension headaches. But, it’s not myopia developing, it’s eye strain.

The muscle around your eyes, called the ciliary muscle, is getting tired. This muscle controls the shape of our lens, allowing it to curve and focus on objects that are close and faraway. Staring at a computer screen for several hours forces our ciliary muscle to keep working, and stay contracted at the same tension for long periods of time. This is quite tiring for the muscle.

The tired ciliary muscle might give you headaches, and difficulty focusing on distant objects. While the mechanism hasn’t been proven scientifically, some researchers think that it might take a while for the muscle to snap out of its contracted state, and relax. While it’s still contracting the lens and cornea will stay curved at a particular point. This means you can only focus on nearby objects.

Another reason for the fuzzy vision is blinking. We normally blink around 10-15 times per minute. But using a computer can drop it to as low as seven times a minute. Blinking spreads tears over the surface of the eye. When we stop blinking the surface of the cornea dries out: clouding the once transparent cornea, and causing blurry vision.

Computers make us particularly susceptible to blurry vision from dry eyes because unlike when we read a paper, we are staring at the computer screen straight on. This increases the surface area of the cornea, making our eyes vulnerable to drying out. (When we read text on paper we are normally looking downwards, and the eyelid covers a large part of the front of our eye, stopping the tears evaporating.)

How long do these symptoms last?

Both the tired ciliary muscle and dry eyes are a short term phenomenon, and only last a few hours. Once we start blinking and relaxing the muscle they go away, with no long term side effects to worry about.

What can you do to prevent eye strain?

Give your eyes a rest. Take regular breaks and look around at distant objects or close your eyes.
Move your computer screen slightly lower than your eyes: this will force you to close your eye lids a little.
Make sure you blink! This prevents dry eyes and stops your cornea going cloudy – keeping your vision clear.

Posted in You and Your Body | 6 Comments

Tit for tat: Can guys lactate?

Posted on September 22, 2009 by Wendy

When it comes to rearing babies, females are given the brunt of the work. We not only hold the little bubs for nine-months while they develop. But females are also responsible for lactating the newborn after it’s born. In sharp contrast, when it comes to fellas – all they need invest is a single ejaculate.

This inequality isn’t a human phenomenon. Males directly care for offspring in less than 10 per cent of mammal species, which begs the question: why do female mammals get the lion’s share of the parental burden? And if males wanted to, could they share the load?

I’m not talking about changing the diaper; I want to know could men lactate?

Darwinian developments

Evolutionarily speaking, there are two reasons that might explain why males haven’t evolved to lactate. One: since babies grow inside the female, males can never be certain that it’s their child they’re caring for. Why expend all that milk for a child that isn’t your DNA? And two, since females are carrying the baby it might be advantageous (for the species) if the male ran off and impregnated another women instead of waiting around for the baby to get thirsty.

But, there are some good reasons that sticking around. Blokes could protect the vulnerable mother in the latter stages of pregnancy. And, it’s been noted that in dogs litter size often matches the amount of milk females can produce. If males developed to lactate, maybe larger litter sizes could develop.

Could guys do it?

We used to think that being pregnant made women lactate, and since blokes couldn’t get pregnant, we figured they couldn’t lactate either. But this isn’t true. It’s the hormones and manual suckling that gets milk flowing. It’s not surprising then that in female animals, lactation can be induced without pregnancy through injecting hormones and/ or suckling.

In theory men just need to make the right hormones, not babies, to start producing milk. And here’s the kicker: men can make the right hormones, and they can produce some milk.

Why do women make milk?

Milk is released from nipples through a hormone called prolactin. During the later parts of pregnancy, levels of prolactin rise. But women don’t release milk until the baby is born because the effect of prolactin is blocked by high levels of progesterone that a mother-to-be is making. At childbirth, levels of progesterone fall, and milk starts secreting from nipples.

According to a 2008 review on male lactation men can make prolactin and even have spontaneous surges of the hormone that reach the same level as females in late pregnancy.

Suckling Swedes

Once lactation begins after childbirth, levels of prolactin in females drop. But nipple suckling from the baby stimulates more prolactin to be released, ensuring a continuous supply of milk.

Manual nipple stimulation can also increase prolactin levels in men. This is good news for Ragnar Bengtsson, a 26 year old man from Sweden, who is currently stimulating his breasts using a breast pump every three hours for three months in an attempt to lactate.

According to the Daily Telegraph, Sigbritt Werner, professor of endocrinology at Karolinska Institutet in Stockholm, said that if he keeps this up a layer of tissue will begin forming beneath the nipple and enough prolactin will be made to release “a drop or two” of milk.

Why only a drop or two?

Milk is stored inside in little sacs inside breasts called alveoli. So to store milk, you need breasts. To make breasts (naturally) you need oestrogen and progesterone, and importantly you need to not have testosterone, which blocks breasts developing. When testosterone levels rise during puberty in males, the actions of typical female hormones on breasts is stopped, so men don’t have the milk storage capacity of women.

But guys can make some milk! So do they ever do it?

Yes! Following disease and deprivation men have actually been observed lactating. Malnourished men in World War II prisoner of war camps lactated after they were liberated and given proper sustenance. Why?

The long term starvation severely damaged their liver, testicles and pituitary gland. But when the men were given nutrition the function of the testes and pituitary gland improved quite quickly, and started doing their job – which is making hormones.

It’s usually the liver’s task to breakdown these hormones if the body doesn’t need them. But the liver recovered from starvation much slower than the other organs. This meant there was a hormonal imbalance that caused men to lactate.

For similar reasons, men with liver cirrhosis and cancers around the pituitary gland have also been observed lactating.

Is it really lactation?

US academics Racey and Racey argue that lactation can only be used to describe milk production that is used to feed offspring. So when men produce a little drop of milk following famine, disease and manual suckling it’s not “lactating”, but a condition called galactorrhoea.

Unfortunately, while men can produce and release milk, there is no male mammal species on the planet that has been shown to produce it in large enough quantities to sustain a newborn’s growth. For some reason, evolution has entrusted lactation to female mammals around the world. And I guess we ought to embrace it.

Cookies anyone?

Posted in You and Your Body | 1 Comment

Stopping the hype: Do kids get high from sugar?

Posted on September 17, 2009 by Wendy

While babysitting in my teens parents always gave me the same instructions: don’t give the kids sharp knives, don’t feed the baby the steak from the freezer, and whatever you do – don’t give the children sugar before they go to bed. The idea that sweets and red cordial makes kids go (sugar) bananas has been around for the last 30 years. But the evidence to prove it is actually pretty scarce.

In fact evidence that sugar can give anyone a “high” is also in short supply. New reviews on old data are saying that the placebo effect and some judgmental parents are to blame for kids missing out their much wanted sweets.

The 70’s: don’t blame the boogie, blame the sugar!

In 1974 a fellow by the name of Crook found that when you took sucrose out of a hyperactive child’s diet their behaviour improved. He then found that when the sugar was reintroduced, hyperactivity and naughty childlike behaviour returned. Four years later, another study showed the same effect. This led scientists and parents alike to conclude that sugar makes kids go hyper. Many smaller studies have also shown a connection between controlled, healthy diets and decrease in hyperactivity.

It was predicted that because refined sugars and carbohydrates enter the bloodstream quickly and make rapid changes in blood glucose levels it might trigger adrenaline production. Adrenaline is a hormone that increases heart rate and blood pressure, bringing more oxygen to the brain, and making kids more active and alert. But, this idea hasn’t been confirmed by rigorous investigations.

Now: don’t blame the sugar, blame the parents (and the researchers)

More recently, scientists are actually changing their tune about sugar’s effect on the body and brain. In 2004, a review on the topic published in the British Journal of Nutrition found that many of the 1970s studies used poor methods. For one, they didn’t have a control group of kids who hadn’t eaten sugar to compare against. And mistake 2: many of them used parents to judge the children’s behaviour after the parents knew their kids took a sugar hit, and know the myth about sugar. (Tainted results!)

Adding some sweetness to the 2004 conclusions, earlier this year a review on the placebo effect found that when it comes to sugar and parental expectations, parents are quite biased. One study tested this bias directly. Researchers gave one group of kids a sweet, nonsugar drink and a parent was told the child had sugar; while in another group the child was given a sweet, nonsugar drink but the parent told the child was not given sugar. On average, the parents who thought their kid drank sugar recorded that their child was more hyperactive and noncompliant than those who thought their little dears didn’t ingest any sugar. Alarmingly (and probably coincidentally) the researchers found that the children, who were expected to go hyper (their parents were told they drank sugar), actually had significantly lower activity levels as measured by a wrist actometer.

Dr. Vreeman and Dr. Carroll, two paediatricians from Riley Hospital for Children wrote in their myth busting book Don’t Swallow Your Gum: Myths, Half-truths, and Outright Lies About Your Body and Health this year (2009, St. Martin’s Press) that there are at least 12 double-blind, randomized, controlled trials (the best, most reliable kind) which examine how children react to diets containing different levels of sugar. According to them, “None of these studies, not even studies looking specifically at children with attention deficit-hyperactivity disorder, could detect any differences in behavior between the children who had sugar and those who did not.”

Sugar and the brain

It also doesn’t make much sense that the human brain and nervous system would be so sensitive to sugar that eating some chocolate or red cordial would significantly change our behaviour. All chemicals that affect our brain are tightly controlled. This makes sure that we keep a (somewhat) constant concentration of different substances in our body. Glucose supply is no different. It’s controlled by complex mechanisms, like hormones and feedback loops. So, for example, if there is too much glucose in the blood from digesting sugar, insulin will be produced to suck it up, keeping a constant concentration of glucose in the blood.

Despite tight control of the chemicals that affect our brain, studies have shown that glucose can actually improve some cognitive tasks, such as attention, information processing, and word recall.

Going red: Could it be the colouring?

If sugar isn’t to blame for hyperactive kids, what is? Maybe it’s the red in the red cordial. In 1977 Feingold hypothesized that additives, like artificial colours and preservatives, caused hyperactivity in children. To test his theory he gave kids a capsule of food dyes, or a placebo for five days and made them perform learning tasks. Some of the children performed worse after receiving the food dyes compared with placebo.

But, the study used a high dose of food dyes (much more than what a child would consume from the regular diet), so we aren’t sure that these results can be generalized to real-life situation. Although an analysis of 15 quality controlled trials of food colourings showed increase in hyperactivity.

The Sweet Conclusion

After all the hype about sugar and hyperactivity there is really not much evidence to back it up. Of course that doesn’t mean that it’s time to ply those kids with candy and cake. Sugar does lead to obesity and can harm your teeth. But no more can parents use the excuse “it’s getting close to bed time” to stop their kids enjoying a late night snack. And for my next babysitting myth? Can I feed babies steak straight from the freezer?

Posted in Food: finding the proof in the pudding | 3 Comments

Can dogs smell fear?

Posted on September 7, 2009 by Wendy

You’re in a dark alley way. You notice a wild dog barking and growling at you. You’re afraid, very afraid. A bead of sweat rolls down your cheek. Just look calm, you think. Then you remember that dogs can smell fear. With one sniff this dog will know that you are terrified, and no amount of looking calm will save you. More sweat appears on your forehead. It’s at this point you think, What if it’s just a myth? What if dogs don’t actually smell fear? Your eyes narrow, looking straight at this puppy. You open your bag and whip out this book. With eye fixed on the dog and another eye on this page, you find out for yourself if dogs, scientifically speaking, can smell fear.

The myth about dogs and their smelling abilities says that if you are afraid, a dog can smell it. It’s as simple as that really. Fear-smelling is a handy ability to have. If you can tell that another animal is scared, they become an easy target. Plus, when animals and humans are incredibly afraid, they can even freeze with fear. For example, studies of mice and rats have shown that these rodents freeze up when they smell strong cat odours. If a dog can take one look at a lilly-livered old rat, and know that he is frozen with fear, that’s dinner on the table before you can say “the only thing to fear is fear itself.” But is it true? Could Inspector Rex really be that clever?

For dogs to be able to smell fear it would mean that animals, including humans, have to make a fear smelling substance. Many animals, from ants to mice to cats, use smells to communicate with their animal buddies and fend off attackers. Weasels and skunks, for example, let out a horrible odour from their anal glands (also called a fart) when foreign intruders are around. Domestic and wild cats do the same. These smells, called alarm pheromones, ward off attackers (and any other creature that has the ability to smell). Alarm pheromones also alert other skunks to the threat to danger. In a bee hive, if a bee detects a foreign odour they will release alarm pheromones, which act like a ‘call to arms.” Bees near the hive will quickly fly to the hive, ready to fight the intruder. If bees, cats and skunks can create fear smelling odours, can humans?

The most recent and relevant study performed on the topic was done in 2002 by the University of Vienna. The researchers placed pads under the arms of females and made them watch a scary movie, Candyman, and a not-so-scary movie, Lokorama. Candyman follows the story of a serial killing clown, while Lokorama follows the journey of a train, as it calmly moves down a track. The researchers removed the pads and asked other females if they could smell a difference (the pads were unlabeled). The females were also asked to describe the smells using a multiple choice questionnaire, which included descriptions like: does it smell like sex, aggression, or fear? The researchers found that the females, for the most part, could tell the difference between the smells. Sweat from the horror film was described as stronger, more unpleasant, and more aggressive than the neutral film sweat. This tells us that we do release different smells in different environments, and that these differences can be detected by other people. But could dogs detect it?

The study didn’t venture into the canine, and no study has gone on to see if dogs react differently to the different smell. But considering that dogs have a particularly strong sense of smell, much stronger than humans, (think of drug searches) it seems that if humans can smell the difference, a dog could too.

It’s also possible that humans don’t actually have a fear scent specifically (after all, it was only one study) but we just release regular sweat when we are scared and dogs can smell it. Many studies show that when humans are afraid we sweat more. This is because our body prepares us to run away from danger, and sweat will allow us to release body heat that will build up as soon as we start to sprint. The strong smell of sweat might be what a dog detects.

Another explanation to the canine myth is that when people say dogs can “smell fear” they got their grammar wrong. Perhaps dog’s sense fears from our behaviour, and don’t smell scents of fear? Maybe they just recognise certain movements, such as backing away, and they know you’re afraid. If this is the case, their sense of fear has nothing to do with smelling skills., which is quite a disappointment.

If a grammatical error is to blame for the myth that dog’s can smell fear that takes the fun out of the whole discussion. In an instant Lassy, Bingo and Inspector Rex have been demoted from creatures with superpowers of smelling deduction, to animals, just like us, that know someone is afraid because of behaviour! No longer are we hostage to their ‘mind reading’ snouts. But, perhaps, like the bee, and the skunk, we also release pheromones of fear that dogs can smell. Only time (and a couple more studies) will tell us if dogs really can smell human fear.

What to do if you meet a growling dog in an alley way

There are many different reasons that a dog may be aggressive. One is fear-induced aggression, where the dog will be aggressive because they are actually afraid of you. A study in 2005 found that if a person approached a dog aggressively, it was more likely respond with antagonistically than if you weren’t forceful. So don’t try to fight fire with fire, and don’t be hostile toward the canine.