tag:theconversation.com,2011:/africa/topics/sweet-6873/articlesSweet – The Conversation2022-01-05T20:01:54Ztag:theconversation.com,2011:article/1731972022-01-05T20:01:54Z2022-01-05T20:01:54ZA taste for sweet – an anthropologist explains the evolutionary origins of why you’re programmed to love sugar<figure><img src="https://images.theconversation.com/files/438857/original/file-20211222-48250-15eo0z2.jpg?ixlib=rb-1.1.0&rect=724%2C155%2C4914%2C3466&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Being able to perceive sweetness can guide foragers to the most calorie-rich picks.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/close-up-of-child-picking-blackberries-royalty-free-image/582364588">Elva Etienne/Moment via Getty Images</a></span></figcaption></figure><p>The sweetness of sugar is one of life’s great pleasures. People’s love for sweet is so visceral, food companies lure consumers to their products by adding sugar to almost everything they make: yogurt, ketchup, fruit snacks, breakfast cereals and even supposed health foods like granola bars.</p>
<p>Schoolchildren learn as early as kindergarten that sweet treats belong in the smallest tip of the food pyramid, and adults learn from the media about <a href="https://doi.org/10.3390/nu8110697">sugar’s role in unwanted weight gain</a>. It’s hard to imagine a greater disconnect between a powerful attraction to something and a rational disdain for it. How did people end up in this predicament?</p>
<p><a href="https://scholar.google.com/citations?user=zhY22GQAAAAJ&hl=en&oi=ao">I’m an anthropologist</a> who studies the evolution of taste perception. I believe insights into our species’ evolutionary history can provide important clues about why it’s so hard to say no to sweet.</p>
<h2>Sweet taste detection</h2>
<p>A fundamental challenge for our ancient ancestors was getting enough to eat.</p>
<p>The basic activities of day-to-day life, such as raising the young, finding shelter and <a href="https://doi.org/10.1086/jar.40.4.3629795">securing enough food</a>, <a href="https://www.nationalgeographic.com/foodfeatures/evolution-of-diet/">all required energy in the form of calories</a>. Individuals more proficient at garnering calories tended to be more successful at all these tasks. They survived longer and had more surviving children – they had greater fitness, in evolutionary terms.</p>
<p>One contributor to success was how good they were at foraging. Being able to detect sweet things – sugars – could give someone a big leg up.</p>
<p>In nature, sweetness signals the presence of sugars, an excellent source of calories. So foragers able to perceive sweetness could detect whether sugar was present in potential foods, especially plants, and how much.</p>
<p>This ability allowed them to assess calorie content with a quick taste before investing a lot of effort in gathering, processing and eating the items. Detecting sweetness helped early humans gather plenty of calories with less effort. Rather than browsing randomly, they could target their efforts, improving their evolutionary success. </p>
<h2>Sweet taste genes</h2>
<p>Evidence of sugar detection’s vital importance can be found at the most fundamental level of biology, the gene. Your ability to perceive sweetness isn’t incidental; it is etched in your body’s genetic blueprints. Here’s how this sense works.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/438841/original/file-20211222-15-1ytc1o3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Microscopic view of cells just beneath tongue's surface." src="https://images.theconversation.com/files/438841/original/file-20211222-15-1ytc1o3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/438841/original/file-20211222-15-1ytc1o3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=399&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438841/original/file-20211222-15-1ytc1o3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=399&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438841/original/file-20211222-15-1ytc1o3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=399&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438841/original/file-20211222-15-1ytc1o3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438841/original/file-20211222-15-1ytc1o3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438841/original/file-20211222-15-1ytc1o3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">Microscopic cross section of the tongue’s surface. Taste buds are clusters of cells embedded beneath the tongue’s surface, facing into the mouth through a small pore (top). Here, the taste bud is the round cluster of cells at center.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/shows-a-single-taste-bud-with-a-taste-pore-facing-royalty-free-image/139826481">Ed Reschke/Stone via Getty Images</a></span>
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<p><a href="https://www.scientificamerican.com/article/making-sense-of-taste-2006-09/">Sweet perception</a> <a href="https://doi.org/10.1038/nrn.2017.68">begins in taste buds</a>, clusters of cells nestled barely beneath the surface of the tongue. They’re exposed to the inside of the mouth via small openings called taste pores.</p>
<p>Different subtypes of cells within taste buds are each responsive to a particular taste quality: sour, salty, savory, bitter or sweet. The subtypes produce receptor proteins corresponding to their taste qualities, which sense the chemical makeup of foods as they pass by in the mouth.</p>
<p>One subtype produces bitter receptor proteins, which respond to toxic substances. Another produces savory (also called umami) receptor proteins, which sense amino acids, the building blocks of proteins. <a href="https://doi.org/10.1007/s12031-020-01642-4">Sweet-detecting cells produce a receptor protein</a> called TAS1R2/3, which <a href="https://sitn.hms.harvard.edu/flash/2013/the-bittersweet-truth-of-sweet-and-bitter-taste-receptors/">detects sugars</a>. When it does, it sends a neural signal to the brain for processing. This message is how you perceive the sweetness in a food you’ve eaten.</p>
<p>Genes encode the instructions for how to make every protein in the body. The sugar-detecting receptor protein TAS1R2/3 is encoded by a pair of genes on chromosome 1 of the human genome, conveniently named TAS1R2 and TAS1R3.</p>
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<a href="https://images.theconversation.com/files/438911/original/file-20211222-21-iuhc43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="black bat hangs upside down from branch, holding fruit" src="https://images.theconversation.com/files/438911/original/file-20211222-21-iuhc43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/438911/original/file-20211222-21-iuhc43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/438911/original/file-20211222-21-iuhc43.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/438911/original/file-20211222-21-iuhc43.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/438911/original/file-20211222-21-iuhc43.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/438911/original/file-20211222-21-iuhc43.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/438911/original/file-20211222-21-iuhc43.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">A fruit bat enjoys a sweet treat.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/one-fiji-flying-fox-isolated-on-white-background-copy-space-news-photo/1095489104">Avalon/Universal Images Group via Getty Images</a></span>
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<p>Comparisons with other species reveal just how deeply sweet perception is embedded in human beings. The TAS1R2 and TAS1R3 genes <a href="https://www.discovermagazine.com/planet-earth/accounting-for-taste-why-a-bear-but-not-a-seal-will-steal-your-cupcake">aren’t only found in humans</a> – <a href="https://doi.org/10.1007/s11434-013-5811-5">most other vertebrates have them, too</a>. They’re found in monkeys, cattle, rodents, dogs, bats, lizards, pandas, fish and myriad other animals. The two genes have been in place for hundreds of millions of years of evolution, ready for the first human species to inherit.</p>
<p>Geneticists have long known that genes with important functions are kept intact by natural selection, while genes without a vital job tend to decay and sometimes disappear completely as species evolve. Scientists think about this as the use-it-or-lose-it theory of evolutionary genetics. The presence of the TAS1R1 and TAS2R2 genes across so many species testifies to the advantages sweet taste has provided for eons.</p>
<p>The use-it-or-lose-it theory also explains the remarkable discovery that animal species that don’t encounter sugars in their typical diets have <a href="https://doi.org/10.1073/pnas.1118360109">lost their ability to perceive it</a>. For example, many carnivores, who benefit little from perceiving sugars, harbor only broken-down relics of TAS1R2.</p>
<h2>Sweet taste liking</h2>
<p>The body’s sensory systems detect myriad aspects of the environment, from light to heat to smell, but we aren’t attracted to all of them the way we are to sweetness.</p>
<p>A perfect example is another taste, bitterness. Unlike sweet receptors, which detect desirable substances in foods, bitter receptors detect undesirable ones: toxins. And the brain responds appropriately. While sweet taste tells you to keep eating, bitter taste tells you to spit things out. This makes evolutionary sense. </p>
<p>So while your tongue detects tastes, it is your brain that decides how you should respond. If responses to a particular sensation are consistently advantageous across generations, <a href="https://doi.org/10.1016/j.cub.2017.11.016">natural selection fixes them in place</a> and <a href="https://doi.org/10.1038/007417a0">they become instincts</a>.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/r2aMf3oTxss?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Even newborns have a preference for sweet and an aversion to bitter.</span></figcaption>
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<p>Such is the case with bitter taste. Newborns don’t need to be taught to dislike bitterness – they reject it instinctively. The opposite holds for sugars. Experiment after experiment finds the same thing: <a href="https://doi.org/10.1097/MCO.0b013e328346df65">People are attracted to sugar from the moment they’re born</a>. These responses can be shaped by later learning, but they <a href="https://www.npr.org/sections/thesalt/2014/03/19/291406696/why-a-sweet-tooth-may-have-been-an-evolutionary-advantage-for-kids">remain at the core of human behavior</a>.</p>
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<h2>Sweetness in humans’ future</h2>
<p>Anyone who decides they want to reduce their sugar consumption is up against millions of years of evolutionary pressure to find and consume it. People in the developed world now live in an environment where society produces more sweet, refined sugars than can possibly be eaten. There is a destructive mismatch between the evolved drive to consume sugar, current access to it and the human body’s responses to it. In a way, we are victims of our own success.</p>
<p>The attraction to sweetness is so relentless that <a href="https://doi.org/10.3389/fpsyt.2018.00545">it has been called an addiction</a> comparable to nicotine dependence – itself notoriously difficult to overcome.</p>
<p>I believe it is worse than that. From a physiological standpoint, nicotine is an unwanted outsider to our bodies. People desire it because it plays tricks on the brain. In contrast, the desire for sugar has been in place and genetically encoded for eons because it provided fundamental fitness advantages, the ultimate evolutionary currency.</p>
<p>Sugar isn’t tricking you; you are responding precisely as programmed by natural selection.</p>
<p></p><hr> <p></p>
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<img alt="" src="https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/439239/original/file-20220103-48418-1p7tcpi.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p><em>This article is part of a series examining sugar’s effects on human health and culture. <a href="https://theconversation.com/us/topics/sugar-2022-114641">You can read the articles on theconversation.com.</a></em></p><img src="https://counter.theconversation.com/content/173197/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Stephen Wooding does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>If you ever feel like you can’t stop eating sugar, you are responding precisely as programmed by natural selection. What was once an evolutionary advantage has a different effect today.Stephen Wooding, Assistant Professor of Anthropology and Heritage Studies, University of California, MercedLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1134552019-04-23T20:13:23Z2019-04-23T20:13:23ZSickly sweet or just right? How genes control your taste for sugar<figure><img src="https://images.theconversation.com/files/270320/original/file-20190423-15218-9to8i9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Genes not only influence how sweet you think something is, but also how much sugary food you eat.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/123816682?src=AXenF6GhIp4jrizZ5_Awdg-1-14&size=medium_jpg">from www.shutterstock.com</a></span></figcaption></figure><p>You might love sugary doughnuts, but your friends find them too sweet and only take small nibbles. That’s partly because your genes influence how you perceive sweetness and how much sugary food and drink you consume.</p>
<p>Now our <a href="https://academic.oup.com/ajcn/advance-article-abstract/doi/10.1093/ajcn/nqz043/5475742?redirectedFrom=fulltext">recently published study</a> shows a wider range of genes at play than anyone thought. In particular, we suggest how these genes might work with the brain to influence your sugar habit.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/fact-or-fiction-is-sugar-addictive-73340">Fact or fiction – is sugar addictive?</a>
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</em>
</p>
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<h2>What we know</h2>
<p>When food touches our taste buds, taste receptors produce a signal that travels along taste nerves to the brain. This generates a sensation of flavour and helps us decide if we like the food.</p>
<p>Genetic research in the past decade has largely focused on genes for sweet taste receptors and whether variation in these genes influences how sensitive we are to sweetness and how much sugar we eat and drink. </p>
<p><a href="https://doi.org/10.1017/thg.2015.42">Our previous study</a> showed genetics accounts for 30% of how sweet we think sugars or artificial sweeteners are. However, at the time, we didn’t know the exact genes involved.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/curious-kids-how-do-tongues-taste-food-103744">Curious Kids: how do tongues taste food?</a>
</strong>
</em>
</p>
<hr>
<h2>What our latest study found</h2>
<p>Our new study looked at data from 176,867 people of European ancestry from Australia, the US and UK.</p>
<p>We measured how sweet 1,757 Australians thought sugars (glucose and fructose) and artificial sweeteners (aspartame and <a href="https://pubchem.ncbi.nlm.nih.gov/compound/neohesperidin_dihydrochalcone">neohesperidin dihydrochalcone</a>) were. We also looked at how sweet 686 Americans thought sucrose was and whether they liked its taste. </p>
<p>We also calculated the daily intake of dietary sugars (monosaccharide and disaccharide sugars found in foods such as fruit, vegetables, milk and cheese) and sweets (lollies and chocolates) from 174,424 British people of European descent in the <a href="https://www.ukbiobank.ac.uk/">UK Biobank</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/270326/original/file-20190423-15221-1hw5opp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/270326/original/file-20190423-15221-1hw5opp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/270326/original/file-20190423-15221-1hw5opp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/270326/original/file-20190423-15221-1hw5opp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/270326/original/file-20190423-15221-1hw5opp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/270326/original/file-20190423-15221-1hw5opp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/270326/original/file-20190423-15221-1hw5opp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/270326/original/file-20190423-15221-1hw5opp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">How many lollies do you eat a day? The researchers combined these types of questions with genome analysis to find links between sugar intake and people’s genes.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/1092965624?src=cL9zC9-ie-rJm9Emlw2ZFw-1-29&size=medium_jpg">from shutterstock.com</a></span>
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<p>Then we looked at the associations between millions of genetic markers across the whole genome and the perception of sweet taste and sugar intake, using a technique known as <a href="https://doi.org/10.1371/journal.pcbi.1002822">genome-wide association analysis</a>.</p>
<p>After a 15-year study, we showed that several genes (other than those related to sweet taste receptors) have a stronger impact on how we perceive sweetness and how much sugar we eat and drink.</p>
<p>These included an association between the <a href="https://ghr.nlm.nih.gov/gene/FTO">FTO gene</a> and sugar intake. Until now, this gene has been associated with obesity and related health risks. However, the effect is possibly driven <a href="https://www.cell.com/cell-metabolism/fulltext/S1550-4131(15)00475-1?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS1550413115004751%3Fshowall%3Dtrue">not by FTO but nearby genes</a> whose protein products act in the brain to regulate appetite and how much energy we use.</p>
<p>We believe a similar situation may be influencing our sugar habit; genes near the FTO gene may be acting in the brain to regulate how much sugar we eat.</p>
<p>Our study suggests the important role the brain plays in how sweet we think something is and how much sugar we consume. That’s in addition to what we already know about the role of taste receptors in our mouth.</p>
<h2>Why we love sweet foods</h2>
<p>Our natural enjoyment of sweet foods could be an evolutionary hangover. Scientists believe being able to taste sweetness might have helped our ancestors identify energy-rich food, which played a critical part in their survival.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/our-ancient-obsession-with-food-humans-as-evolutionary-master-chefs-42899">Our ancient obsession with food: humans as evolutionary Master Chefs</a>
</strong>
</em>
</p>
<hr>
<p>However, being able to taste sweetness doesn’t always mean you prefer to eat lots of sweet-tasting food. </p>
<p>So it looks like there are genes associated with the consumption of sweet foods, but not how sweet we think they are, such as FTO. There might also be genes that influence our perception of sweetness but not how likely we are to eat sweet food.</p>
<h2>Regional differences</h2>
<p>We were surprised to find genes for sweet taste receptors had no effect on either the ability to taste sweetness or on the amount of sugar consumed in our study, which looked only at large populations of European descent.</p>
<p>But by comparing people of different ancestries in the UK Biobank, we showed there was some variation between different populations that variations in genes for sweet taste receptors might explain. For instance, we found people of African descent tended to eat more sugar than people of European and Asian descent.</p>
<h2>So, how can we use this?</h2>
<p>Just like genetics can help explain <a href="https://theconversation.com/why-you-like-coffee-and-i-choose-tea-its-in-the-genes-106854">why some people choose tea over coffee</a>, our latest study helps explain why some people prefer sweet food. That could lead to personalised diets to improve people’s eating habits based on their genetics.</p>
<p>However, genetics is not the only factor to influence your taste for sugary foods and how much of these you eat or drink. So you can’t always blame your genes if you’ve ever tried to quit sugary drinks or snacks and failed.</p><img src="https://counter.theconversation.com/content/113455/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Daniel Liang-Dar Hwang is affiliated with The University of Queensland and QIMR Berghfoer Medical Research Institute. </span></em></p>People with a sweet tooth can (partly) blame their genes for their sugar habit. New research shows how the brain also gets involved.Daniel Liang-Dar Hwang, Postdoctoral Researcher, The University of QueenslandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/314862014-09-09T14:31:02Z2014-09-09T14:31:02ZMost birds can’t taste sugar – here’s why the hummingbird can<figure><img src="https://images.theconversation.com/files/58571/original/t5c8zg4h-1410262572.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Other birds are missing out</span> <span class="attribution"><span class="source">Maude Baldwin</span></span></figcaption></figure><p>Chickens are not fussy eaters. Any object resembling food is worth an exploratory peck. But give a chicken the choice between sugary sweets and seeds, and they will pick the grains every time. This is odd. Many animals, including our own sugar-mad species, salivate for sugar because it is the flavour of foods rich in energy. New research suggests that many birds’ lack of interest in sugar is down to genes inherited from their dinosaur ancestors.</p>
<p>Most vertebrates experience sweet taste because they possess a family of genes <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2721271/">called T1Rs</a>. The pairing of T1R1 and T1R3 detects amino acids and gives rise to the savoury “umami” taste, and the T1R2-T1R3 pair detects sugars and gives us our sweet tooth.</p>
<p>Maude Baldwin, a postgraduate student at Harvard University, searched the genomes of ten species of birds from chickens to flycatchers. She found that insectivorous and grain-eating birds possess the gene pair that detects the amino acids present in insects and seeds, but none had the T1R2 gene responsible for the ability to taste sugar. These modern birds <a href="http://evolution.berkeley.edu/evolibrary/article/evograms_06">evolved from carnivorous theropod dinosaurs</a> whose diets were rich in proteins and amino acids, but lacked sugar. So Baldwin reasoned that without a need to detect sweetness, ancient birds lost their T1R2 gene.</p>
<p>Hummingbirds appear to have bucked the trend. Every day they consume more than their own body weight in nectar. They can taste the difference between water and a sugar solution within a quarter of a second. And they also like the flavour of non-sugary artificial sweeteners like erythritol and sorbitol. How is this possible if they have no gene for sweet taste?</p>
<p>To answer this question, Baldwin cloned taste receptors from the sugar-insensitive chicken, from hummingbirds, and from the hummingbird’s closest relative, the insect-eating chimney swift. Her results have been published in the journal <a href="http://dx.doi.org/10.1126/science.1255097">Science</a>. She discovered that while the t1r1 and t1r3 receptors in swifts and chickens only respond to amino acids, the same receptors in the hummingbird fire in response to sweet-tasting sugars, sugar alcohols and the artificial sweetener sucralose, but not to amino acids.</p>
<p>Baldwin found that mutations in the hummingbirds’ T1R1 and T1R3 genes have switched them from savoury to sugar detectors. These mutations appear to be under positive selection, that is the proportion of protein-altering mutations is greater than we would expect by chance.</p>
<p>Hummingbirds have co-opted genes that originally allowed dinosaurs to savour the taste of flesh, and transformed them into the sugar detectors most modern birds live without.</p>
<p>Charles Darwin, <a href="http://darwin-online.org.uk/content/frameset?pageseq=31&itemID=CUL-DAR126.-&viewtype=image">scribbling in the rough notebooks</a> to which he would later refer when writing the Origin of Species, pondered how animals in new environments learn which foods are worth eating and which should be avoided. He concluded that this problem drove the evolution of a sense of taste: “Real taste [in] the mouth, according to my theory must be acquired by certain foods being habitual – hence become hereditary.”</p>
<p>Baldwin’s results show that Darwin was spot-on. Perhaps ancestral hummingbirds that lacked the sweet receptor frequented flowers to catch insects. On occasion they accidentally consumed some nectar. Small mutations in T1R1 and T1R3 would have allowed them to taste this sugary liquid, giving them access to a vital source of energy. This could have given nectar-sipping individuals the evolutionary upper hand compared to insect-eaters.</p>
<p>Future research may focus on other nectar-eating birds such as sunbirds and lorikeets, and frugivores like tanagers, and whether they have undergone the same mutations as hummingbirds, or if a different mechanism explains their penchant for sugary foods.</p><img src="https://counter.theconversation.com/content/31486/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hannah Rowland has received funding from NERC, The Royal Society, The British Ecological Society, and The Winston Churchill Memorial Trust.</span></em></p>Chickens are not fussy eaters. Any object resembling food is worth an exploratory peck. But give a chicken the choice between sugary sweets and seeds, and they will pick the grains every time. This is…Hannah Rowland, Lecturer in Ecology and Evolution, University of CambridgeLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/285502014-07-01T05:00:22Z2014-07-01T05:00:22ZHow to make strawberries sweeter without adding calories<figure><img src="https://images.theconversation.com/files/52641/original/s869zpkx-1404126709.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Sugar is not the secret to sweetness.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/settme3/4748421253/sizes/l/in/photolist-8eAUcX-2CCufX-2CBWnK-8eAUm2-5uap9w-8aFL71-8VyMeN-5GZFew-4sdY8m-4X8M3J-8aCwrR-8uXp7e-9NsCqJ-2CC4YV-8uXpKZ-4X4tLM-6SxJt6-6geSQD-5kTZKV-4X4tQZ-5rYJUY-7TT1Xh-4oi9rU-8v1rXs-6xmo9u-7Utg4V-cC3aD3-9kgVnF-abCzyH-3bWhGq-s2pUD-eiNo6k-8vfWTJ-9GKvD1-iXpH1F-4SvD7D-MGAa8-7Kmxq1-ECGmA-6dXLLd-9FGqY-5SP4x2-5RFfFs-4SzRN1-eBf4k-eBf2n-65HWDq-5RFfpQ-4SzREq-2guV5/">Yodatheoak </a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-sa/4.0/">CC BY-NC-SA</a></span></figcaption></figure><p>Strawberries and cream are symbolic of Wimbledon and appreciated worldwide for their oh-so-sweet flavour. Researchers at the University of Florida, including myself, studied more than 30 varieties of strawberries and found that what makes them so sweet is not just sugar. We have identified a handful of chemicals that can make strawberries sweeter, without needing to increase the amount of sugar in them.</p>
<p>The sense of smell depends on our interaction with thousands of chemicals that we are surrounded by every day. We interact with them when we stop to smell a rose or when we take a drink of lemon juice. These are volatiles – chemicals which diffuse in the air – that are responsible for fragrance and flavour. Volatiles that increase perception of sweetness without adding sugar will have far-reaching effects in food chemistry, and also provide targets for breeding improved flavour in strawberry and other fruits. </p>
<h2>It’s all about ingredients</h2>
<p>The sense of taste allow humans to take a chemical inventory of food or drink in the mouth. When we consume we qualify these chemicals in terms of savoury, salty, bitter, sour and sweet. Smell enriches these flavours. And it does so when we chew and swallow food or drink, because volatile chemicals are forced up the back of the throat to the nasal cavity, which triggers smell upon exhalation. This is called the “retronasal” path.</p>
<p>In the brain, different areas receive different sensory information. In the case of taste and smell, there is some overlap. For instance, sensory information from the tongue and retronasal smell overlap, whereas “orthonasal” smell, which is inhaling through the nostrils, acts independently. It is the integration of taste and retronasal smell that gives rise to how we perceive flavour. </p>
<p>Genetic distinctions between varieties of strawberries create different flavours through levels of sugars, acids and volatile chemicals. There are thousands of varieties of strawberry available today. Much of this genetic diversity exists as a result of more than 250 years of breeding. </p>
<p>At the University of Florida Plant Innovation Program, we wanted to capture this diversity of strawberry flavours and determine the sensory effects on consumers. Perhaps we could find that ingredient which results in a more preferable strawberry. So, over two years, we cultivated more than 30 genetic varieties of strawberries and tested them. </p>
<p>We recorded the amount of different types of volatile chemicals, sugars and other chemicals in each type of strawberry. Then we asked 100 consumers to score each sample for its hedonistic and sensory properties. Our results have been published in the journal <a href="http://dx.doi.org/10.1371/journal.pone.0088446">PLOS ONE</a>.</p>
<h2>Making strawberries sweeter without adding sugar</h2>
<p>We found, not surprisingly, that the total sugar content in strawberries is the most predictive of sweetness intensity. However, we were surprised that, among the potential 300 volatiles, only a handful contributed to the intensity of strawberries’ flavour.</p>
<p>The volatile linalool, for instance, was found to be associated with strawberry flavour intensity, and is also found in orange blossoms and blueberries. Another volatile, mesifuran, is strongly associated with strawberry flavour and has been focus of research strawberry research for a while.</p>
<p>The best part of the study was that we identified specific volatiles in strawberry that make contributions to perceived sweetness independent of sugar concentration in the fruit. These sweet enhancing volatiles, such as 1-penten-3-one, had been overlooked in the past. </p>
<p>Our research has identified these individual volatile chemicals which greatly enhance the perceived strawberry flavour and sweetness intensity independent of sugar. These effects are happening in a retronasal manner rather than orthonasal. The sensory integration of retronasal smell and taste happening in the brain allows certain volatile chemicals to influence perceived sweetness.</p>
<p>These findings are being used by the University of Florida breeders to develop more flavourful and sweeter varieties of strawberries. Screening volatile chemicals in strawberry selections can ensure that newly developed varieties offer the best “recipe” to consumers. Also, the identification of genes responsible for the presence or quantity of specific volatiles will allow for the development of molecular markers, a type of genetic testing. Maybe in the near future the Wimbledon strawberry tart will not need extra sugar.</p>
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<p><em>Next, read this: <a href="https://theconversation.com/its-fruit-but-not-as-we-know-it-how-bubbleberries-can-look-like-strawberries-and-taste-of-gum-26247">These strawberries taste like bubble gum</a></em></p><img src="https://counter.theconversation.com/content/28550/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael Schwieterman is a postdoctoral researcher at the University of Florida for the Department of Environmental Horticulture and Plant Innovation Program. This work is supported by grants from USDA Specialty Crop Block Grant.</span></em></p>Strawberries and cream are symbolic of Wimbledon and appreciated worldwide for their oh-so-sweet flavour. Researchers at the University of Florida, including myself, studied more than 30 varieties of strawberries…Michael Schwieterman, Postdoctoral Research Fruit Flavor Biochemistry and Genetics, University of FloridaLicensed as Creative Commons – attribution, no derivatives.