Tag Archive for lab

The bitter truth – now in genotype form!


Isn’t this a fantastic scenario: you’re sitting at your desk and a mysterious white powder floats through the air and lands on your face. Some of it lands on your lips and, being the risk-taking individual that you are who is apparently not averse to putting unidentified powders in your mouth, you taste it and immediately complain to your colleagues about how disgustingly bitter it is. The powder has landed on their faces too and they taste it too and… no, it doesn’t taste of anything, actually. It’s not bitter in the least, they say to you with suspicious eyes and 50% of their eyebrows raised. Well then, aren’t you quite the weirdo? Please take your imaginary bitter taste and go sit in the corner.

This is how they discovered that people can experience tastes quite differently from each other. It was only 1930 when A.L. Fox accidentally released some phenylthiocarbamide into the air in his lab while trying to create an artificial sweetener and it landed on the faces of his colleagues (good work!), and while some of them complained of its bitterness (you’d think that would be the least of their problems if they’re working in a lab where chemicals routinely drift onto their faces and into their lungs), Fox himself couldn’t taste the bitterness. It turned out that about 30% of people find phenylthiocarbamide tasteless, whereas the rest find it moderately to intensely bitter.

It’s not exactly uncommon knowledge now that the ability to taste bitterness varies from person to person and that this is down to genetics. A whole heap of studies over the years have looked at how genetic variants within the TAS2R family of genes mean that some people taste bitterness of particular substances more easily than others. For TAS2R38, the gene that codes for the protein that allows phenylthiocarbamide to be tasted, you can have one of three possible combinations of variants, allowing you to be either a non-taster, a medium taster, or… a supertaster, in which case you can taste that phenylthiocarbamide better than about 75% of the population! Well done, you.

So, like I was saying, we know bitterness perception varies from person to person due to genetics, but it’s kind of boring if you just look at that within the scope of “Oh, Person X can taste this very specific chemical really easily whereas Person Y can’t taste it at all”. Pretty limited relevance. The interesting part is how it affects behaviour — how well you can taste bitterness can affect how much you like particular foods, and that can have a reasonably big impact on eating behaviours.

Studies have been a bit inconclusive when it comes to bitterness gene variants and liking for somewhat bitter vegetables (such as broccoli, spinach, Brussels sprouts, kale and cucumber), with high-tasters of bitterness sometimes liking these vegetables more than low-tasters, and sometimes less. However, sensitivity to bitterness changes with age, so maybe you need to look at these things in particular age groups to get a clearer picture. Certainly, some studies have found that in children, non-tasters who aren’t so sensitive to bitterness find these vegetables more pleasant to eat than the tasters who are sensitive to bitterness, and non-tasters generally eat more vegetables than tasters. Some studies have found the same in adults.

Consumption of bitter fruits can also be affected by genes, with female adult supertasters finding a drink containing naringin (a compound from grapefruit peel) less pleasant, and the same went for just plain grapefruit juice. It looks like the intensity of the bitterness matters too, since taster children were no different from non-taster children when drinking a mixture of 25% grapefruit juice and 75% orange juice, but then the tasters disliked a more bitter mixture of 50% grapefruit juice and 50% orange juice compared to non-tasters.

So it all sort of makes sense — people who are more sensitive to bitterness kind of dislike things that are a bit bitter. However, the intrigue continues with research that has found that genetic variants for bitterness are also associated with different perception of sweetness and saltiness and sourness, the detection of the pungency or flavour of food, and also the ability to discriminate fat content in food and drinks.

But I will go into detail for those in future posts, and for now, you can make some Pimm’s Cup cupcakes. Complete with whipped lemonade and simulated cucumber! It’s a bitter orange and cucumber gel, cut into sticks, to which I attached real cucumber skin. Don’t you want to do something so convoluted and arduous too?

Read on for the recipe for Pimm’s Cup cupcakes.

Sweet sounds

These yuzu chocolate mud cakes with fizzy yuzu icing may be my favourite thing I’ve baked in a long time. The texture of the cakes is ridiculous (it’s kind of like peanut butter, in that it sticks to the roof of your mouth in a delightfully and irritatingly luxurious way). And yuzu, well, I currently pay $40 for a 300ml bottle of yuzu juice (weep!) but I’ve just tracked down Australia’s only yuzu grower, who just happens to be about a 2-hour drive south from here, so if I had a car I would probably be there right now (and possibly passed out amongst the rinds of the dozens of yuzu fruit I had gorged on) but I’ll have to wait a little longer until I can beg/borrow/win a car. Then… everything I cook will have yuzu in it.

Ev-er-y-thing.

Alright, so. Enough yuzu, more science.

Eating food is a multisensory experience. (Hurr durr derp derp that’s pretty obvious.) It’s all pretty damn important when it comes to the perception of food and the enjoyment of eating: the look, the smell, the taste, the texture. But who’s the lonely sense who’s been left out of the party? It’s hearing! Poor, neglected hearing. He wants to come to the party too. He wants to consort with the other senses with reckless abandon. Why won’t you let him? Why won’t you letttt himmmm?

We might not think much about hearing’s contribution to food (beyond the pleasing crunch of crunchy things — more on that in a future post) but it turns out that the brain doesn’t exclude hearing from the party completely. In fact, our brains make implicit associations between tastes and sounds. We might not be aware of them on a conscious level (is a sweet taste high-pitched or low-pitched?) but with the right sort of task, as provided by experimental psychology, we can get a look at the furtive, illicit dalliance between hearing and taste. How thrilling.

So the task is like this. You sit at a computer with your hands on the keyboard. Words are going to flash up one after another on the screen, and they’ll either be sweet words (words like sugar, honey, maple syrup) or salty words (words like salt, crisps, pretzel). Sometimes you’ll also hear sounds played over some headphones (2 seconds of sound played on an instrument such as a violin, piano or bassoon). The sounds will either be high-pitched or low-pitched. You and some other participants start off the experiment on Condition 1, then change to Condition 2 (while other participants will start on 2 and change to 1).

Condition 1
Press the A key if: you see a sweet word or hear a high-pitched tone.
Press the L key if: you see a salty word or hear a low-pitched tone.

Condition 2
Press the A key if: you see a sweet word or hear a low-pitched tone.
Press the L key if: you see a salty word or hear a high-pitched tone.

You as a participant probably won’t notice anything amazing during the experiment. But when the researchers look at your reaction times (i.e. how fast you were at pressing the correct key after you saw a word or heard a sound) they’ll notice something very interesting. You responded significantly faster in Condition 1 than in Condition 2.

For some reason, you’re faster when a sweet word and a high-pitched tone are associated (Condition 1) than when a sweet word and a low-pitched tone are associated (Condition 2). Likewise, you’re faster when a salty word and a low-pitched tone are associated (Condition 1) than when a salty word and a high-pitched tone are associated (Condition 2). Somehow, the sweet-high and salty-low combinations just make more sense to your brain, enabling you to react and identify them more quickly — and more accurately, since participants made fewer errors in Condition 1 (although the error rates in Condition 1 and 2 weren’t significantly different statistically).

Another study using the same kind of experiment found a significant association between sour words and high-pitched sounds, and between bitter words and low-pitched sounds. However, these researchers have also tested sweet, sour, salty and bitter altogether using a different task, and the pitch associations for salty and bitter disappeared, although the associations between sour words and high-pitched sounds and between sweet words and high-pitched sounds were still there. Hmm.

And it seems like we don’t really have a good explanation for why the brain does this. There are plenty of ways of drawing parallels between properties in different senses — for example, when comparing hearing to vision, the loudness of a sound might be thought of as the equivalent of the brightness of a colour, since increased loudness and increased brightness are both experienced by us as being more “intense”. So maybe we just don’t have a good enough grasp of the properties of taste to be able to figure out something like why sweet is somehow a parallel for high-pitched. Is there a biological basis to the association? Or is it cultural somehow? Do people from different cultures experience the same associations? Would the results be any different if actual tastes were used (e.g. a bit of sugar on the tongue) instead of taste-related words?

And… and… can we influence the perception of taste by using sound? If the basis of the association is biological, maybe closely connected or overlapping brain regions are responsible for sweet tastes and high pitches. There certainly is overlap between the hearing and taste sensory pathways, not just at later stages of cortical processing but in the early stages too, as the primary taste cortex (which I discussed in my previous post) is located partly in the insula, which also plays a pretty big role in auditory processing (Bamiou et al. 2003).

So it’s a big and tenuous jump, but… can we influence the perception of taste by using sound? If the association is due to neuronal connectivity, would something taste sweeter if we played high-pitched music compared to low-pitched music? Or would something just taste wrong somehow if sound that wasn’t associated with it was played? Intriguing possibilities…

Recipe for yuzu chocolate mud cakes with fizzy yuzu icing under the cut. Recommended serving suggestion: high-pitched sounds, naturellement.

Of beer and butterbeer

So, you’re a research participant and you’ve signed up for a “verbal styles” experiment in your local university psychology department. Good on you! Those guys always need participants, so thank you for being so generous with your time. In this experiment, you’re given a list of words and you just have to read each word, think of a synonym, then write the synonym down. Pretty simple.

Ok you’re done. Awesome. How easy was that? We’ll be able to analyse your verbal styles now. And now that you’re finished, just wait around for half an hour or so because we’ll need to take some follow-up measurements in a bit.

Actually — oh. Oh no. There’s been a cancellation in another study and a participant in that one has dropped out and we need a replacement. It’s just a taste-testing experiment about beer. It’ll only take 10 minutes. Can you do it? Yes? Brilliant!

So you’re taken to another room where that experiment is being conducted. There are three different beers* — A, B and C — in non-descript disposable cups and you just need to drink some of each and rate them using a questionnaire about how sweet or dry they are, how carbonated they are, etc.

Ok now you’ve done that, we’ll go back to the other room for the follow-up measurements for the other experiment. Cool.

Well, then. Have you guessed what’s happened? Did you have an inkling that all of that, from the word lists to the beer tasting, was part of one big experiment? Maybe you did, but the participants who went through that exact scenario in a study by Zack and colleagues sure didn’t.

The important thing here is that during the word list part of the experiment, different participants were given different kinds of words to come up with synonyms for. Some people had lists with words related to negative mood and emotion, some were given lists with words related to positive mood and emotion, and some people had lists with just neutral words.

And the interesting thing was this: participants exposed to lists of negative words (e.g. anxious, sad) during the list experiment consumed significantly more beer during the tasting than those who were exposed to lists of positive words (e.g. happy) or neutral words (e.g. frequent). Simply priming people with negative words is enough to make them drink more.

(Oh god, don’t look up “sad” in a thesaurus!)

It seems that maybe negative words and their associated moods are tied in closely enough with the consumption of alcohol that just being exposed to the words primes drinking behaviour — mentioning these negative words incidentally activates the brain’s representation of alcohol consumption, although not at a conscious level. And this is in young university students, not in problem drinkers who regularly use alcohol to cope with negative situations (although everyone in the experiment did complete a questionnaire about drinking behaviour and some participants were classified as having some problem drinking symptoms).

This association between negative mood and drinking is interesting because you would kind of think that, for a lot of people at least, drinking is associated with positive times (celebrations, parties, etc.) so exposing people to positive words would prime their drinking behaviour because positive mood and drinking are associated. But it didn’t — maybe because positive mood is associated with the context of celebrations and parties generally (e.g. having a lot of people around and socialising), so alcohol doesn’t factor in directly in that case. Yet somehow, perhaps through cultural constructs and influences, the brain seems to unconsciously think that being in a negative mood calls for alcohol! So…

Cheerful! Joy! Puppies! Happy fun ball!

Now that you’ve read those words and don’t feel like drinking… make some butterbeer curd to go with salty, buttery, delicious madeleines. I came up with butterbeer curd just the other day, given that I’ve already made proper butterbeer before, based originally on a charming Tudor recipe from 1594. My next post will be about the actual butterbeer recipe itself! Ooooh, ooooooh, the intrigue.

Recipe for butterbeer curd and salted madeleines after the cut.

KNOW YOUR CHOCOLATE

(Epic post ahoy!)

Hello, come in, come in, please, come in and make yourself comfortable. How are you? Good? Good. Are those new mittens? They’re lovely. Can I offer you a drink, maybe a Pimms No. 1 with over-sized cucumber garnish? No? Would you like a delicious biscuit? Ok, here’s a delicious biscuit.

Now that you’re comfortable and have a delicious biscuit…

… we need to talk.

Please assume the brace position, as this is heavy news.

Chocolate is probably not that good for you. The antioxidants and all that good-for-you-heart stuff, well… it’s not all it’s made out to be.

There’s been a gargantuan 18-wheeler truckload of stuff in the media about how eating chocolate is good for you. Why is it good for you? It’s got antioxidants! Antioxidants that, well, they stop your body from ageing… and stuff. They stop your cells from getting attacked by, um… nasty things! They prevent cardiovascular problems. Chocolate is full of antioxidants so chocolate prevents cardiovascular problems! Right? Right?

Well, maybe, maybe not. I’m sorry, but it’s just not black and white like that. (It so rarely is with science. Sigh.) There is plenty of research being conducted into the cardiovascular-protective properties of chocolate consumption, and it’s been going on for a fair few years now. Unfortunately, the evidence is not conclusive, and we’re starting to realise that the research that’s gone on so far isn’t anywhere near detailed enough to tell us about whether we should eat chocolate for its cardio-protective qualities, and if so, how much.

It’s true that a fair few studies have found results like “consumption of dark chocolate is correlated with a reduction in blood pressure”. But! (There’s always a but in science, damn it.) When you look at the studies overall, there are a lot of problems.

The number of people in a lot of the studies is quite small, so that increases the chances that we might be seeing false positives in the results, i.e. we think we see a relationship between chocolate consumption and cardiovascular health but actually there isn’t one. The results we have so far just don’t allow us to reliably conclude that chocolate consumption definitely does (or does not) improve cardiovascular health in any specific way.

Some of the studies are conducted over a pretty short time period. These are acute intervention studies that only look at the effects of dark chocolate consumption over a few days (and for those few days, maybe people in the study are paying better attention to their health and stress levels purely by virtue of being in a study that draws attention to those aspects of their lives). These short studies don’t tell us much about the long-term effects of chocolate consumption on either cardiovascular health or other important aspects of health. Need more info.

The amounts of chocolate that should be consumed to achieve any reported improvement in blood pressure or whatever are all over the place. Some studies say you need to eat 2 squares a day to improve blood pressure, but don’t have more than 2 because that doesn’t improve blood pressure. Some studies say you need to eat a few squares daily, whereas others say you only need 10 square per month. It’s a big confusing mess, really. In fact, we’re not even sure if there are enough antioxidants in chocolate to have any impact on overall antioxidant levels in the body — studies that show antioxidants improve cell health in cell cultures in a dish in a lab have used antioxidant concentrations many many times greater than what could be achieved in the human body by eating chocolate. Basically your stomach would be exploding in chocolate pyrotechnics if you ate enough chocolate to get the same concentrations as the cells in the lab were being dosed with. I’d prefer not to explode, quite frankly.

And something that’s emerging as a major flaw in this research is that we don’t know the exact levels of antioxidants in different chocolates. We know dark chocolate is probably highest in antioxidants, but there’s a huge range of variation in the amounts depending not just on percentage cacao, but also how the cacao was treated and processed and where it originally came from. For example, some processing methods can radically reduce the key antioxidant compounds such as catechin and epicatechin. So essentially, when a study is done to see whether chocolate consumption results in improved health measures, we don’t actually know what sort of dose of antioxidants these people in the study are getting!

The upshot of this is that we can’t possibly recommend a particular amount of chocolate to consume in order to get health benefits — we don’t know what amount of antioxidants is in any given chocolate, and we don’t know what the ideal dose of antioxidants is anyway.

Alright, so antioxidants play an undeniably important role in the health of the human body. But here’s the thing: just because something is necessary for health, doesn’t mean that big amounts of it are good for you, and that even bigger amount are better. In fact, it’s usually quite the opposite.

If there’s one thing you learn this year about science and health, make it this: a lot of things are on what’s called an inverted-U curve. It’s not a linear trend of more = better. It’s more like not enough is bad, enough is good, too much is bad again. However, we have to do an enormous amount of research to establish what “enough” actually is. At the moment, we’re trying to work out what “enough” is for antioxidants, but it’s safe to assume that too much is probably a bad thing.

In fact, an enormous review was done of the antioxidant research. Bjelakovic and colleagues did a systematic review and meta-analysis of studies that looked at what happened when people were given antioxidants supplements. This means that they looked at a whole heap of studies, kicked out the ones that weren’t rigorous enough, then tried to figure out the bigger picture that the well-conducted, rigorous studies were painting. They looked at 68 of these good-quality studies, which altogether tested the effects of antioxidant supplementation (in the form of beta carotene, vitamin A, vitamin C, vitamin E or selenium) in 232,606 people. With that many people, surely you’ve got the ability to detect even tiny little relationships between the antioxidant supplementation and health outcomes.

And the results of this enormously powerful meta-analysis? Some antioxidant supplementation might cause bad health outcomes, whereas others still have an unclear effect. Still! After all those studies and all those people! There was no clear benefit to taking extra antioxidants. This could be because: (a) there’s no relationship between extra antioxidants and the health variables being measured, (b) the relationship is so small and subtle it’s difficult to detect or (c) the effects are dependent on other variables that we aren’t taking account. My money’s on (c).

So it’s kind of scary when you think about how frequently the media and various companies (with a financial interest in getting us to buy their products) tell us we should be indiscriminately cramming antioxidants every which-way into our bodies. (Goji berries! You need goji berries! Or was it acai berries that were the latest superfood du jour? Oh god just get some pomegranate before it’s too late! Don’t you want to live forever?) It’s entirely unsurprising that most of us have absorbed the inaccurate message that antioxidants are always good for us and we need as big a dose as we can get.

But even though we don’t know what the right amount of antioxidants is for optimal health benefits (yet), and even though we don’t know what precise levels of antioxidants are in various products, and even though we’re surrounded by products with labels zealously screaming “FULL OF ANTIOXIDANTS!”, and even though we don’t know if we’re getting too little or too much, don’t despair! What should you do? It’s old and tired and not that interesting, but it’s the truth: eat a balanced diet and eat things in moderation. If you do that (along with some exercise) you’ve got a very good chance of getting pretty much everything you need to achieve very good health. If you’re eating tomatoes and carrots and that sort of thing and maybe a bit of dark chocolate here and there, you’re probably getting the antioxidants you need. Don’t fret!

So maybe, eventually, research will be able to pin-point exactly what daily dose of antioxidants we should aim to get, and whether we can eat chocolate to get some of that dose. Until then, don’t use “it’s good for me!” as an excuse to eat chocolate. If you’re leading a generally healthy lifestyle, you can eat it chocolate just because you enjoy it — you don’t need much more justification than that, right?

Thank you for your time. And now: a recipe.

Recipe for not-actually-superfood cookie sandwiches under the cut.

Taste in the face

There’s no art
to find the mind’s construction in the face.

Macbeth, Act 1 Scene 4

I might be going out on a limb when I suggest that Shakespeare probably wasn’t a neuroscientist. I’m sure I can find some Shakespeare conspiracy theorists to tell me how wrong I am and that Christopher Marlowe was also a talented geneticist in between writing Shakespeare’s work, but for that line in Macbeth to suggest that our faces do not betray our thoughts and feelings and intentions indicates clearly that Shakespeare had a very poor understanding of modern social neuroscience research between the 1970s and 2010. How embarrassing for him.

These are “Old Fashioned” snickerdoodles, based on the sweet and bitter taste combination of the Old Fashioned cocktail. (This recipe is from the book The Boozy Baker, which Dan bestowed upon me after returning from a social cognition workshop via NYC and San Francisco — thanks, Dan!) One interesting bit of research looking and both sweet and bitter tastes found some very intriguing results about how our faces react to those tastes, and also how changing our emotional state changes our ability to perceive tastes. Who would have thought — eating is tied in with feelings! (Hi to all the other emotional eaters out there. Let’s have a piece of cake to celebrate how interesting neuroscience research is!)

In a study by Greimel et al., researchers video-recorded people’s facial expressions as they were drinking either a sweet chocolate drink, a bitter quinine drink, or a bitter-sweet carbonated drink. (The chocolate drink was Müllermilch Schoko and the carbonated drink was Schweppes Bitter Lemon, if you’re planning on replicating this experiment in the comfort of your own home or laboratory.) The researchers later watched these videos and scored a range of particular facial movements (brow lower, lip press, upper lip raise, etc.) to see what people did with their faces when they tasted a bitter or sweet taste.

In a not highly surprising result, sweet and bitter tastes elicited different facial expressions. Bitter tastes warranted brow lowering and lip raising just prior to swallowing, then brow lowering and mouth opening after swallowing, and on the odd occasion, a smile, presumably by the people cynically amused by their unfortunate situation of having to drink something gross like quinine. Sweet tastes reliably resulted in lip sucking before swallowing, lip wiping after swallowing, and of course, smiling (including the Duchenne smile, which is when you smile with your eyes as well as your mouth — yes, it has a name!).

So the specifics are interesting but overall, none of this is all that surprising — we all make the faces too and we’ve all seen other people make the faces. But the other thing the researchers did was that after people had tasted all the different drinks, they were shown one of two movie clips. One group was shown a clip that was intended to make them feel happy, whereas the other group was shown a clip that was intended to make them feel sad. Then — they tasted the different drinks again.

And what did this show? It showed that changing someone’s emotional state makes them perceive tastes differently. More specifically, people who had watched the happy clip then found the sweet chocolate drink even sweeter and more pleasant. People who had watched the sad clip then found the sweet chocolate drink less sweet and less pleasant. How nice this chocolate drink tasted was dependent on whether the person was a bit happier or a bit sadder.

This was not the case, however, for the bitter-tasting drink. Watching the happy movie clip or the sad movie clip didn’t change people’s ratings of how bitter or unpleasant the drink was. A potential explanation of this is that sugary sweetness plays with the neural wiring of our emotions a bit more because the brain wants to reward us for seeking out energy-rich sugar by giving us a pleasant, hedonic experience after we eat something sweet. Bitterness, on the other hand, doesn’t really need that kind of emotional involvement. It might play a role in telling us what foods to avoid, since bitterness can be associated with toxins in the things that our ancestors might have been jamming in their mouths to see if they were any good for eating — but if something is bad for us, and it tastes bitter when we eat it, and then we get physically sick from it, that association between the bitter taste and physical sickness is an association that doesn’t need more subtle emotional prompting from the brain to make us realise to not eat the bitter berries next time or we’ll end up with our stomach contents on our feet. Bitterness also doesn’t reliably tell us much about nutritional value of food. So if we want to learn to avoid something that could potentially kill us, probably better to not just have our brains’ perception of that bad taste be susceptible to our emotional state (and probably better to have a more emphatic response to bad food, rather than our brains just making us a feel a little bit sad after eating something potentially deadly).

So the next time you’re on a hedonic quest for enjoyment through the wonders of cake, chocolate, ice-cream, whatever, pre-emptively enhance your experience by watching something heart-warming or hilarious. If you wish to adhere to the rigours of scientific research, you can even use the exact movie clip used in the experiment in elicit the happy state. It’s this one.

References
Greimel et al. (2006). Facial and affective reactions to tastes and their modulation by sadness and joy. Physiology & Behavior, 89, 261-269.

Recipe for “Old Fashioned” snickerdoodles under the cut.