The science of taste, enjoyment and health

Why taste is so important to nutrition

Healthy, nutritious foods are often perceived as tasting “bland”, while discretionary or unhealthy foods are portrayed as being full of enjoyable flavour, as aptly described by American actor and film-maker Robert Redford in his famous quote: “Health food may be good for the conscience, but Oreos taste… a lot better” Redford (2023).

Throughout history, sweet cakes and cookies have been used in birthday celebrations from the ancient Egyptian Kahk cookies for the sun God Ra on birthdays to Geburstgorten birthday cakes specifically baked for children in Germany in the 1400s, a tradition that has spread globally and remains well entrenched in societal norms (Sugar.org, 2023). Beyond nutrition, taste is the main factor that differentiates healthy foods from discretionary foods. Aristotle (350BC) is credited with defining taste in terms of either sweet or bitter, and influenced by odorous characteristics like oily, pungent, harsh, sour, sharp or acidic (Polansky, 2007). Until the science and understanding of the functions of the human body was determined, our tongue has been our main guide throughout millennia, helping us differentiate safe food from potentially hazardous foods. Since the days of Aristotle, science has come a long way in understanding the tongue, the science of taste, and how taste affects food intake and hence, nutrition and health.

The fundamental reason why we come back to eating certain foods, and steer clear of eating others is taste. Hence taste has just as much importance on dietary intake and human health as nutrition because our taste-experiences largely govern our eating behaviours. Taste by definition is both the physiological “sense that perceives and distinguishes the sweet, sour, bitter, salty, or umami quality of a dissolved substance” via taste buds of the tongue, but is also used to describe the emotional attachment to “liking or a preference” for something whether it be the taste of a particular food, genre of music, style of clothes, or type of sport ("Taste," 2023a; "Taste," 2023b). Ultimately, taste preferences are influenced by cultural and societal norms. While the taste of a food is independent to its nutritional composition, nutrient rich foods are often perceived as “tasteless”, whereas discretionary foods are positioned as “tasty” which is highly influenced by the emotional sensations (e.g. pleasure, joy, disgust) that are aroused. To be clear, it is possible to enjoy delicious nutrition than endure blandness in the name of "health." The food industry focuses on understanding the components in foods that trigger taste, the role of different foods in society (e.g. cake and celebrations), and the emotional influences that drive behaviours. Fundamental to understanding the science of taste and the pleasure of eating is the tongue and its role in helping us choose or steer clear of different foods.

... our taste-experiences largely govern our eating behaviours.

Gatekeeper to taste: The tongue

Of our five senses (sight, hearing, touch, smell, taste), sight and smell affect our perception of what a particular food will taste like even before we touch or bite it. Historically, these two sense have been crucial in determining what is safe (or not safe) to eat and drink (Beidler, 1952; Lawless, 2005). Nevertheless, our tongue remains the most important gatekeeper to what we eat and drink. The tongue has two roles:

1. a motor skill muscle that helps with chewing and swallowing, and articulation of words when speaking and singing; and

2. an information sensor for our brain (Doyle et al., 2023).

The taste and texture of foods and drinks we consume is first assessed by our tongue and the information received is relayed to our brain, which in turn determines if it safe to eat/ drink, if it is an enjoyable experience, or in the case of bitter products like coffee, if we are capable of learning to enjoy it.

The tongue is lined with papillae, and it is the papillae that give the tongue its rough surface (Figure 1A) (Cenveo, 2023; Doyle et al., 2023; Lawless, 2005).

The taste papillae are split into groups at different locations on the tongue (Cenveo, 2023; Doyle et al., 2023; Lawless, 2005):

• Back of the tongue in a V-shape: Circumvallate (sometimes known as vallate) papillae

• Sides and ridges of the tongue: Foliate papillae

• Across the top surface of the tongue: Fungiform papillae and Filiform papillae.

Apart from filiform papillae which do not contain taste cells, the other taste papillae contain taste buds and essentially are clustered balls of up to 100 taste cells which are renewed weekly (Figure 1B) (Cenveo, 2023, Hadley, Orlandi, & Fong, 2004; Stańska & Krzeski, 2016). The oral cavity of the mouth (made up of the tongue, palate and epiglottis (the little flap of cartilage that appears to be hanging at the back of the mouth)) has roughly 5000 to 10 000 taste buds with over 50% of them are located on the tongue (Stańska & Krzeski, 2016). However, the number of taste buds varies between individuals, and those with higher taste sensitivity have more fungiform papillae and taste buds in general (Lawless, 2005; Miller Jr & Reedy Jr, 1990).

Miller Jr and Reedy Jr (1990) were able to categorise individuals as supertasters, normal tasters, and non-tasters based on the number of fungiform papillae on the tongue using blue food colouring dye (Figure 2). Their method has been used to create a standard test protocol where the front part of the tongue is covered in blue food dye (Figure 2).

The fungiform papillae will emerge like pink bumps against the blue filiform papillae background. A 6mm hole is placed on the dyed tongue, and the fungiform papillae are counted. If there are 33 or more, the taster is considered a super taster, 15-30 is considered normal, and less than 15 is considered a non-taster (McMahon, 2008).

At the top of each taste bud is a taste pore where microvilli (tiny hair-like structures) protrude and react with different chemicals in foods and drink (Figure 1C) (Cenveo, 2023; Doyle et al., 2023). The microvilli have special chemical channels that detect specific compounds in foods:

Salty : sodium chloride, magnesium, potassium

Sweet : glucose, fructose, lactose, certain amino acids used to build proteins, certain alcohols, artificial sweeteners including aspartame and stevioside

Bitter : a range of alkaloid and polyphenol compounds usually found in plants flavonoids (including caffeine), glucosinolates and quinine

Sour : organic acids (e.g. lactic, citric, acetic acids) and inorganic acids (e.g. hydrochloric, nitric, sulfuric acids, etc.)

Umami : amino acids, in particular glutamic acid or aspartic acid.

This information is passed to the brain via four different sensory nerve pairs located at the base of each taste bud (Figure 1C). The four nerve pairs may explain why our sense of taste is fairly robust throughout life even if our other senses (hearing, sight, touch) decrease with trauma, disease, and/or aging.

The brain assesses the chemicals on our taste buds, determining the flavour of what we tasted, and whether it is safe to consume and enjoy, or if it is unpleasant and possibly unsafe (Doyle et al., 2023; Hadley, Orlandi, & Fong, 2004; Lawless, 2005).

All sensory cells in the taste buds can detect all basic tastes. However, they differ in levels of sensitiveness. For example, one particular cell may be more sensitive to sweet, then bitter, followed by salty and acidic, then umami, and lastly fatty while another cell will have a different sensitivities.

Given “the full experience of flavour is produced only after all the sensory cells from the different parts of the tongue are combined,” we have a “virtually limitless palette of flavours” to explore in the foods and drinks we produce, design and consume (InformedHealth.org, 2016).

The sixth taste sensation: Oleogustus

We have a new taste sensation added to the list: oleogustus – the taste of fat (Doyle et al., 2023). Oleogustus has nothing to do with a fatty mouthfeel, greasiness or texture. While the actual mechanism of action in the taste bud is still being determined, current research has identified fat-specific receptors (Keast & Costanzo, 2015). It appears that the receptor responds specifically to linoleic acid, a fatty acid commonly found in sunflower, soya bean, and corn oils, as well as meat fats including beef. On its own, oleogustus is considered a largely unpleasant taste (Doyle et al., 2023). However when combined with sweet or umami tastes, it can be a tastebud delight with foods like chocolate and donuts to hot chips and steak. Recent research by CSIRO (2020) found grain fed Wagyu beef contains significantly higher linoleic acid than other beef types, which could be contributing to the pleasurable sensory experience associated with eating Wagyu.

Research into the how the fat taste sensation affects human behaviour is early. It appears that oleogustus is unappealing to both human and rat consumers when tasted alone. Yet when combined with other tastes, fat seems to enhance aspects of those other tastes (e.g. deepen the umami flavour notes in steak). Nevertheless, consumers with a high sensitivity for detecting the taste “fat” appear to have either a lower tolerance for eating large amounts of high fat foods or become satisfied faster (Keast & Costanzo, 2015; Running, Craig, & Mattes, 2015). How our tongue's sensitivities affects satiety (feeling of fullness), intake, and health outcomes is still in the early days of discovery.

The French Paradox

The 1980s was a decade marked by the collapse of the Soviet Union, Ronald Regan moved from Hollywood to the White House, the birth of internet took place and “The French Paradox” was coined by epidemiologists who could not understand why heart disease deaths and BMI (body mass index, an arbitrary measurement for determining healthy weight for height) were low in France even though the French consumed more dietary cholesterol and saturated fat than most western countries (Ferrières, 2004; Rozin et al., 2003) (Figure 3).

Despite the Americans being the most focused on health with very little focus on the pleasure of food, consumed the most “diet” (low calorie) foods, they still had the highest rates of coronary deaths, BMI and binge drinking (Rozin et al., 1999; Rozin et al., 2003). The French on the other hand focused the least on health, the most on the pleasure of eating a diverse range of good quality food, and while their portion sizes were smaller, they still spent almost 40mins longer per day eating than the Americans.

Key factors that were determined from The French Paradox include the nutritional properties of different types of fat, a role of high vegetable and fruit intake, and the importance of regular exercise, low smoking and binge drinking behaviours. However a fundamental factor that is intertwined in French culture is their attitude to food, with a major focus on savouring good quality foods that provide sensory pleasure (Ferrières, 2004).

Food, mood and pleasure

The relationship between mood, physiology and food is complex and needs to take into consideration an individual's psychological state, where they are located physically, the pressures of life they may be experiencing, and/or if they are late for an appointment and need to rush to eat, or have sufficient time to savour the moment and the meal. Assuming everything is fine, and all personality and psychological traits have been accounted for, the sensations of different tastes can be associated with different experiences – e.g. sweet and pleasant, sour and surprise, bitter and repulsive (Gibson, 2006). Nevertheless, the pleasurable attributes from different foods is entirely due to the contextual experience of the eater. For example, inmates on death row often express in their last meal choice a desire to relive a better time, a happier memory. Jones (2014) explored why so many inmates choose specific cakes, cookies, pies, ice-cream and milkshakes in their final meal on death row. Taste sensations in addition to textures, aromas and mouthfeel seem to be a physical trigger for emotional comfort that comes from pleasant memories of a happy occasion, a holiday, a first date, a childhood game, a favourite relative like grandma. The pleasurable eating experience is influenced by the memory and emotionality associated with it.

Similarly, elderly patients with dysphagia (difficulty swallowing) have benefited from 3D printed food for the same reason: foods that look like something they recognise (as opposed to slop on a plate), and tastes like foods they know and have eaten before (in addition to being easy to swallow). Tasty, visually appealing, recognisable foods created using 3D printing technology is helping decrease food refusal and prevent malnutrition in these elderly patients (Pereira, Barroso, & Gil, 2021; Smith, Bryant, & Hemsley, 2022).

“When it comes to our deepest desires, it turns out that food isn’t just about taste” (Stein, 2007). There are many other factors at play, including societal norms and nutrition. However if we have a bad taste experience with something, it’s really hard to go back for seconds. “…the sensations of when we felt happiest or most loved…if someone can hand us those memories, it’s the culinary equivalent of a big hug” (Stein, 2007). Whether you are a super taster or average, your tongue and its microscopic tastebuds have the ability to detect both possible poisons as well as an unlimited array of flavour experiences, while triggering emotions and creating memories. Let your taste buds savor each bite: your memory and health will thank you for it.

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Author: The Food Scientist, Dr Anneline Padayachee