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NUTRIDATE

Volume 33, Issue 2 2022

NUTRIDATE

Volume 33, Issue 3, 2022

Why Do We Favour Some Flavours?

Stephanie Osfield: Counsellor, Teacher and Health Journalist

Every time you eat or drink, your genes and evolution are influencing the flavours you like and also how intensely you taste them.

Figure 1: People taste food and drinks differently, and this is impacted by genes and evolution.

Say you’re buying food to take to a movie marathon with friends, but you only have enough money for chips or chocolate. What do you choose – the sweet or salty snack? This may seem like a random decision, but the flavours you most often crave can be impacted by surprising factors.

Back when we lived in caves and food was scarcer, people hunted and gathered to survive. Sense of taste developed over aeons to protect humans from eating a poisonous berry or rancid meat from a mammoth found yesterday. It also helped keep people alive by making energy-providing foods the most appealing, so that they would seek them out and have more body fuel to survive. That is why, millennia later, we crave and desire sweet foods.

In this modern world, our brain still quickly discerns when we should throw milk out because of harmful bacteria growth that could make us sick. It may also save the life of a child who tries to eat a plant but spits it because it tastes bitter, which their brain codes as dangerous.

Figure 2: Evolution taught us to be wary of bitter food that could be poisonous, like these berries, although many bitter foods are good for us.

Flavour Detection

The tongue is wrapped top and bottom in tiny little bumps called ‘papillae’ (the Latin word for ‘pimple’). Just below the surface of these bumps are your taste buds and each person has between 2,000 to 10,000 of them in their mouth. Taste buds are also found on the throat and soft palate (or roof of the mouth) and recently, some have been discovered in the gastrointestinal tract.

Just as a smoke detector is alerted when it senses smoke from burned toast, taste buds rapidly kick into action the moment any substance enters the mouth. Each taste bud houses 50 to 150 special receptor cells with nerve fibres that connect to the brain. Working like culinary detectives, they rapidly analyse all the food or drink that is consumed. Then they fast-track messages to the brain to report whether the substance is safe to chew/drink, swallow and digest. If your brain sends back an alert, it may also send messages to direct you to spit the food out straight away in case it is poisonous.

Figure 3: The tongue is covered in taste buds that connect to the brain.

While eating or drinking, these messages are sent from the taste buds along two different brain pathways. One leads to the limbic system or ‘lizard brain’ which is the first area of the human brain that developed. It is wired for survival, so it imprints memories about flavours in food and drink that made us feel unwell in the past so that we quickly recognize them and do not consume them. The other brain pathway leads to the ‘gustatory cortex’, which identifies and processes information about tastes and recognizes different flavours in food. Though complex, this dual pathway taste detection process happens within moments and it involves:

1. Microvilli: These super-sensitive hairs help the taste buds do a quick analysis of the food’s flavour and send a very fast message which tells the brain if the food or drink is safe to swallow.

2. Saliva: The process of chewing food makes the mouth produce more saliva, which is released by saliva glands and contains chemicals that start breaking food down. This changes a salad sandwich or spaghetti Bolognese to a more liquid state and as this process is happening, the taste buds immediately start to analyse the flavours in this saliva soup.

3. Taste-Sensing Cells: These are clustered together in the taste buds and they do a quick check of any new flavour – whether from a medicine or a product like toothpaste. These cells can wear out and may become damaged if we eat or drink something too hot that burns our tongue, so the body makes new receptor cells every 10 to 30 days. On their surface, some receptor cells have proteins and they bind to some of the chemicals in food, which assists the taste-sensing process.

4. Sense of smell
Together, our tongue and nose enhance the taste experience. The tongue tastes food chemicals using taste buds, while airborne molecules which arise from the aroma of food strongly influence how that food tastes. These odours actually create tiny particles in the air that are ‘sensed’ by special sensory cells in the mucous membranes of the inside roof of each nostril in the nose. At the same time, smells from food are also sensed at the back of the mouth, where they then pass retronasally, (up the back) into the nose. The nose then forwards these electrical signals on to the olfactory (smell) centre of the brain. This is the reason why you can’t detect the flavour of food when your nose is blocked due to a cold or flu.

The Five Primary Flavours

Evolution – which involves a process where bodies and brains adapt and change to survive – has hard-wired human brains and taste buds to prefer some flavours over others. These main flavours fall into two different categories described below.

Figure 4: Taste buds are attuned to different flavours

Tastes We Are Hardwired To Prefer:

Sweet

Food Examples: Sugar, honey, fruit (such as grapes, bananas and apples) and sweet vegetables (such as pumpkin, corn and sweet potato), sweet snacks such as lollies, ice cream and sweet biscuits.

Have you ever wondered why people tend to crave chocolate rather than kale? Back when people lived in caves, they had little access to sweet energy-boosting foods, so when they stumbled across some honeycomb or a patch of wild strawberries, they ate more of these foods to give their bodies an immediate boost of energy. Eating one or two serves of sweet foods while people had access to them also provided additional energy reserves to sustain them for the coming days in case they could not gather or catch enough to eat.

Figure 5: Naturally sweet food used to be hard to come by so our ancestors developed a taste for them to provide a boost of energy.

So, humans developed a sweet tooth to help stay alive and ensure the survival of our species. Unfortunately, in the present day, this sweet tooth can be a liability for our health because processed, sugar-laden foods such as lollies and chocolate bars are highly concentrated and readily available 24/7. When too much sugar or corn syrup or similarly sweet ingredients are consumed, the body may store the excess as fat, which can lead to weight gain and increase the risk of conditions such as diabetes Type 2 and heart disease.

Salty

Food Examples: Eggs, cheese, fish, shellfish, seaweed, beef and snack foods such as salted crisps, almonds and corn chips.

Sodium (commonly known as salt), is essential for many body processes, which is why we innately enjoy this flavour. It helps us maintain the right level of fluid in our body and bloodstream, can stabilise blood pressure and assists the relaxation of certain muscle fibres in the heart and blood vessels so that blood can be pumped around the body more efficiently.

Figure 6: Salt is an important mineral that we need for the body to function well, so it is healthy to have salty food in moderate doses.

Body salts need to be replenished daily as they are lost through bodily functions such as perspiration. Without regular salt intake, we would not survive – so when our body gets low on salt it sends a message to the kidneys and sweat glands to hold on to fluid to ensure there is enough sodium for the body to function.

Unfortunately, salt deficiency is now rare. Our taste buds are bombarded with hidden salt in processed foods, including canned soup, breakfast cereal and snacks. At the dinner table, we shake more salt on our meals. This over-consumption is hurting many people’s health. While it’s important, excess salt intake can stiffen blood vessels, cause high blood pressure and increase risk of heart attack and stroke.

Umami

Food Examples: Meat, mushrooms, soy sauce, Parmesan cheese, anchovies.

The umami flavour was first given a name in 1908, by a Japanese chemist called Kikunae Ikeda, who worked at Tokyo University. He identified umami as a dominant flavour in foods like cheese, meat and asparagus as well as a Japanese food called kombu.

Umami is an appealing savory taste that comes largely from amino acids in food, especially a natural chemical called glutamate. We are hardwired to like the umami flavour because protein is broken down into amino acids. We use amino acids to build and repair muscles and bones and produce important hormones and enzymes that help our bodies function every day.

Figure 7: Umami is an appealing savoury taste that is found in mushrooms, soy sauce, Parmesan cheese and other tasty foods.

Fat

Though it is not officially listed as one of the primary five flavours, some scientists now believe that fat should be considered the sixth main flavor, because receptors for fat have recently been found on the tongue. Research suggests that evolution has hardwired our brains to like the flavour of fatty foods such as hot chips, full cream milk and the crispy skin on baked chicken.

Fats provide energy in the body and essential fatty acids such as omega 3 fatty acids found in fish and are important for healthy functioning of all the body’s cells. Recent research at Rutgers University also suggests that stress, depression and anxiety may dull the ability to taste fat, making people crave more fatty foods to satisfy that taste perception in their taste buds.

Figure 8: Some scientists think fat should be considered a sixth taste as receptors for it have been found on the tongue, and healthy fats are very important.

Tastes We Acquire And Learn to Like

As the following flavours are often found in poisonous plants or contaminated, spoiled foods, we enjoy them less and are more wary of them in our food:

Sour

Food Examples: Lemons, limes, vinegar, yoghurt, wine, grapefruit and pickled foods.

When we taste sour foods, our taste buds act a little like a chemical pH tester and respond to the hydrogen in the acids contained in the food. As sourness is often a sign of food spoiled by bacteria, we are not hardwired to love sour foods and many people take years before they enjoy them. Yet in recent times, sour fermented foods have become very popular because of their health benefits.

Foods like yoghurt, sourdough bread, kimchi (a Korean fermented vegetable dish) and sauerkraut (pickled cabbage) contain active healthy bacteria (such as Lactobacillus in different strains, for example, Bulgaricus and planatarum, which benefit gut health, immunity and physical and mental wellbeing).

Figure 9: Fermented foods have a sour flavour that some people don’t like, but they are very healthy for you.

Bitter

Food Examples: Broccoli, cocoa, beer, eggplant, rocket, Jerusalem artichoke, kale, dark chocolate, endive, dandelion tea, daikon radish, coffee beans.

To protect themselves from being eaten by bugs, animals or humans, plants often contain bitter chemicals in their leaves, stems and flowers or buds, which warn predators that they may be poisonous. This information has been hard-wired into human brains, making bitterness the least appealing flavor.

Figure 10: Foods like broccoli and Brussels sprouts and some leafy greens like kale have a bitter flavour and are full of healthy nutrients.

Yet research shows that some bitter foods such as coffee have a wide range of health benefits. They may also boost bile production in the pancreas, an organ that is very important for processing fats from food. Bitter, cruciferous foods such as Brussels sprouts and broccoli also have health benefits. They contain phytonutrients including sulfates and soluble dietary fibres, which can help stabilize blood sugars and boost good bacteria in the gut where many important hormones are made.

Are Your Taste Buds Firing or Cruising?

Just as some people are naturally faster at running, some are naturally more sensitive when tasting food. This is due to genes inherited from our parents. So, if although everyone may be eating the same sausages and salad at a BBQ, the food will taste different to each person depending on which one of the following categories they belong in:

Supertaster or Hypertaster:

Supertasters have a larger number of taste buds in their mouth, which means the different flavours in food may often taste more intense to them. In particular, they taste bitter flavours more intensely, so they often dislike foods such as dark chocolate, broccoli, cabbage, coffee, grapefruit and bitter lettuces such as rocket and radicchio. Because they receive a stronger burst of flavour from food, supertasters often steer clear of overly sweet or spicy flavours – some find eating curry almost painful.

The term ‘super-taster’ was originally coined by an expert in food science called Professor Linda Bartoshuk, when she was at Yale University. Using a bitter chemical called PROP (6-n-propylthiouracil), she found that 25% of the population are extremely sensitive to the taste of this chemical, and that women are more likely to be hyper-tasters (35%) than men (15%).

On the up side, hypertasters may be less likely to overeat because their many taste buds send strong signals their brain, which then triggers the release of leptin – a hormone that switches off appetite. Unfortunately, some supertasters may steer clear of numerous vegetables because they find them a little bitter, reducing their intake of some healthy nutrients, vitamins and minerals.

Figure 11: Some people have more taste buds than other people, which makes food and drink taste very strong.

Low/Mild/Non-Taster or Hypotaster

In her research using the PROP chemical to test sensitivity to taste, Professor Baroshuk found that around 25% of people can’t taste PROP or can only barely taste its bitter flavour – so there are roughly the same number of non-tasters in the general population as supertasters. These hypotasters have less than the average number of taste buds. To compensate for their lack of taste sensitivity, they enjoy and seek out strong flavours, such as chilli and pepper. They might add lashings of seasoning to meat or pour a large amount of dressing on their green salad without finding the taste strong or too tart.

Unlike supertasters, hypotasters don’t have as many strong food likes and dislikes and are far less fussy eaters. However, they may be more prone to overeat because their taste buds send a weaker signal to the brain. This means that after a snack or a meal, their brain may release less leptin to tell their stomach it is full.

Studies suggest low tasters have a higher preference for high-fat, high-kilojoule foods, such as fast food and snack foods and that they tend to eat more sweet foods than supertasters, increasing their risk of dental cavities and possibly, weight gain. As they are less sensitive to the bitter taste of nicotine, they may also be more likely to become smokers.

Aside from this, research suggests that people who are deficient in two important neurotransmitters in the brain, called serotonin and noradrenaline, may have less ability to distinguish between bitter, sour, and sweet tastes.

Figure 12: Other people have fewer taste buds and can develop a preference for food high in salt and sugar and be prone to overeating.

Medium/Average Taster

Around 50 percent of the population fall into this category. When exposed to the PROP chemical, they can distinctly taste that it is bitter, but do not mind this. Medium tasters generally do not find the bitter flavour in food so intense that they feel a strong aversion to bitter foods or drink. Average tasters tend to enjoy all the main flavours without finding any of them too overwhelming. As they can discern different flavours, they are less likely than low-tasters to over-salt or over-sauce their food and are more likely to receive a robust release of the hormone leptin after meals to switch off their appetite. They are more open than super-tasters to trying new foods and eating a variety of different cuisines, and do not need to have their coffee as strong as low tasters or add more sugar because they are trying to mask the bitterness, like supertasters.

Figure 13: Whatever taste buds you have, you can train yourself to enjoy healthier options.

Did You Know
Research shows that we can manipulate our own taste buds to prefer healthier options. This process may require some patience. It can take 3-6 months to alter your preferences to like healthier food and up to 10 exposures to a new food or taste you don’t like before you accept or actually start to enjoy it.

Student Activities

1. Name the five primary food flavours and give three food examples for each.

2. Draw a diagram of your mouth and show where your taste buds are located.

3. What are papillae and what do they look like?

4. Explain why we evolved to like sweet foods.

5. Why does having a cold affect your sense of taste?

6. Write a short ‘just in’ news bulletin explaining why fat may be the sixth main food flavour.

7. Keep a food diary over a week. Divide the page into columns for each flavour – sweet, salty, umami, fat, sour, bitter. After each meal or snack, tick which flavours it contained. At the end of the week, tally up which flavours you consumed the most.

8. Research amino acids found in umami flavoured foods. List five important things they do in the body.

9. Devise a print media ad promoting the health benefits of broccoli.

10. Count your taste buds: This can be done in class or at home. For this experiment you will need:

– Food dye and a small container to pour it into

– A cotton bud

– A small piece of cardboard roughly the size of your tongue with a hole cut in it by a hole punch.

– A hand mirror

– A mobile phone

– Divide into pairs and both wash your hands with soap. Then you should both:

– Pour a little food dye into a non-porous glass or plastic container and dip your cotton bud into the dye.

– Hold up your hand mirror so you can see your tongue and use the cotton bud to cover your tongue with dye.

– Place the cardboard with the small hole over your tongue, pressing it firmly so that a little bit of your tongue pokes through the hole. Ask your partner to take a photo with your mobile phone then count the number of large bumps on the section of tongue that is poking through the hole.

Results:

– Less than 15 bumps means you are a non-taster

– 15 to 30 bumps means you are an average taster

– 30 bumps or more means you are a supertaster.

References and Resources

ABC News. Super Tasters, Non Tasters and How Your Tongue’s Bumps May Affect Your Appetite:
https://www.abc.net.au/news/science/2018-08-21/supertaster-non-taster-test-your-tongues-bumps/10139528

Australian Academy of Science. Take A Tour Of The Tongue. https://www.science.org.au/curious/people-medicine/how-do-our-tastebuds-work

Australian Academy of Science: Accounting For Taste: How Does Our Sense of Taste Work and Why Do We Have Different Tastes?

https://www.science.org.au/curious/people-medicine/accounting-taste

Cambridge University Press Genetic Variation in Taste Perception: Does It Have A Role In Healthy Eating?

Duke Sanford World Food Policy Centre. E29: Linda Bartoshuk on Supertasters, Yuck, and The Future Of Food Nutrition
https://wfpc.sanford.duke.edu/podcasts/linda-bartoshuk-supertasters-yuck-and-future-food-nutrition

Harvard. T.H, Chan. School of Public Supertasters and Non-Tasters Is it Better to Be Average?

https://www.hsph.harvard.edu/nutritionsource/2016/05/31/super-tasters-non-tasters-is-it-better-to-be-average

Live Science: Tip Of the Tongue: Humans May Taste at Least 6 Flavours:

https://www.livescience.com/17684-sixth-basic-taste.html

National Centre for Biotechnology Information: How Does Our Sense Of Taste Work?

https://www.ncbi.nlm.nih.gov/books/NBK279408/

Scientific American: How The Sense of Taste Has Shaped Who We Are. https://www.scientificamerican.com/article/how-the-sense-of-taste-has-shaped-who-we-are/

Smithsonian Magazine: A Matter Of Taste: https://www.smithsonianmag.com/science-nature/a-matter-of-taste-180940699/

The Conversation. A Taste For Sweet – An Anthropologist Explains the Evolutionary Origins of Why You’re Programmed To Love Sugar.
https://theconversation.com/a-taste-for-sweet-an-anthropologist-explains-the-evolutionary-origins-of-why-youre-programmed-to-love-sugar-173197

Bartoshuk, L. M., 2002. Comparing Sensory Experiences Across Individuals: Recent Psychophysical Advances Illuminate Genetic Variation in Taste Perception. Chemical Senses. 2000 Aug;25(4):447-60. doi: 10.1093/chemse/25.4.447.

Breslin, P. A., 2013. An Evolutionary Perspective On Food and Human Taste

Supertaster experiment. Current Biology. https://doi.org/10.1016/j.cub.2013.04.010

Diószegi, J., Llanaj, E., Ádány, R. 2019. Genetic Background of Taste Perception, Taste Preferences and Its Nutritional Implications: A Systematic Review. Published online 2019 Dec 19. doi: 10.3389/fgene.2019.01272

Depoortere, I., 2014. Taste Receptors of the Gut: Emerging Roles in Health and Disease. Gut, (BMJ) 2014; 63:179-190.

Keast, R. S. J., Costanzo, A. Is Fat The Sixth Taste Primary? Evidence and Implications. Flavour 4, Article number: 5 (2015) 

Klok, M. D., Jakobsdottir, S., Drent, M. L. The role of leptin and ghrelin in the regulation of food intake and body weight in humans: a review. 2007 Jan;8(1):21-34. doi: 10.1111/j.1467-789X.2006.00270.x.

Spence, C. 2015. Just How Much Of What We Taste Derives From The Sense Of Smell. Flavour volume 4, Article number: 30 (2015) 

Eldeghaidy, S., Thomas, D., Skinner, M., Ford, R., Giesbrecht, T., Thomas, S., Hort, Joanne., Francis, S. An automated method to detect and quantify fungiform papillae in the human tongue: Validation and relationship to phenotypical differences in taste perception. Physiology & Behaviour. 2018 Feb 1; 184: 226–234. 

doi: 10.1016/j.physbeh.2017.12.003

Sollai, G., Melis, M., Pani, D., Cosseddu, P., Usai, I., Crnjar., Bonfiglio, A., Barbarossa, I. T. 2017. First Objective Evaluation Of Taste Sensitivity To 6-n-propylthiouracil (PROP), a Paradigm Gustatory Stimulus in Humans. Scientific Reports. 7, Article number: 40353 (2017) 

Tepper, B. J., Barbarossa, T, I. 2020. Taste, Nutrition and Health. Nutrients, 2020 Jan; 12(1): 155. doi: 10.3390/nu12010155

Vennerod, F. F. F., Nicklaus, S., Lien, N., Almli, V. The development of basic sensitivity and preferences in children. Appetite. 2018 Aug 1;127:130-137.

doi: 10.1016/j.appet.2018.04.027. Epub 2018 May 3.

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