Sweet or savoury? 10,000 things that drive our food cravings
Our taste buds are tiny, but they have a huge impact on our flavour preferences and our enjoyment of food. Dietitian Glenn Cardwell explains how they work — and how to retrain them for your health’s sake.
Those of you who watched Australian television in the ’80s may remember the margarine ad that told you to turn your bread upside down because “your taste buds are on the top of your tongue”. Actually, they’re all through your mouth, but most of the 10,000 or so are concentrated on the top of your tongue.
Each taste bud has a taste pore, a small opening through which liquids come into contact with taste-receptor cells. This explains why you taste soup or ice cream instantly, but you need saliva to help you taste a dry food. (More on saliva later.)
The taste-receptor cells in taste buds have a lifespan of just eight to 12 days, meaning they renew themselves three times a month. So when a friend asks you what’s new, you can say “Well, since I last saw you, all my taste buds”, then watch their face.
As you may already know, we have distinct taste buds to detect the sweet, sour, salty and bitter flavours of foods. Certain areas of the tongue are more sensitive to specific tastes. At the tip of your tongue, for example, there’s a cluster of sweet and salty receptors. Even so, all kinds of taste buds are distributed throughout the mouth and over the tongue. You may be less familiar with the fifth taste — umami, which is the flavour of some common savoury foods, including parmesan, tomato paste, meat, Vegemite and mushrooms. The Japanese first used umami, which means deliciousness, to describe specific savoury flavours in 1909; Western cultures didn’t recognise umami as a separate taste until the ’80s.
Food, fragrant food
Our sense of smell is equally if not more important to our taste and enjoyment of food. Smell enables us to differentiate between, say, a peach and a mango, despite their similar sweetness.
Aromas from our food travel up the nose, where they meet olfactory receptors. In humans, these receptors are a lot more sensitive than the taste receptors, so many foods stimulate the scent receptors much more than they do the taste buds, thereby complementing the overall taste sensation. Of course, you already knew that, because when you suffer through a cold, food loses much of its flavour. Having a blocked nose dulls the scent receptors, yet has no effect on your taste receptors.
The truth about our sweet tooth
In general, sweetness comes from sugars (obviously) and small proteins. The most famous example of the latter is the sweetener aspartame, which is a very small protein made up of just two amino acids, aspartic acid and phenylalanine. Although most people consider aspartame to be artificial, amino acids are protein’s building blocks and naturally present in many foods.
Come Easter, you’ll start to feel your sweet tooth ‘twitching’ as you covet your chocolate stash. Having a preference for sweet foods is normal; in fact, we have it from the day we’re born, from our very first taste of sweet breast milk. We’re hardwired to love sweet foods because they’re pleasurable and healthy. Think of fruit and root vegetables; even prawns have an innate sweetness.
Sweet foods’ kilojoules also give us lots of energy, which was essential to human evolution as we established new homelands. These days, manufacturers take advantage of our natural sweet tooth by making most of their treat foods taste sweet.
To let your taste buds help you nibble a little less chocolate this Easter, choose a dark variety. Its high cocoa content provides not only more antioxidants, but also intense flavour, so just a few squares satisfy cravings. Some of dark chocolate’s intense flavour comes from bitter compounds in the cocoa. Similar compounds are also present in coffee and in hops (in beer). Many poisons in nature taste bitter, so scientists speculate that the bitterness is to stop us from becoming sick (as well as avoid Brussels sprouts!).
The ability to taste bitter compounds varies among individuals and can change with age, but give an infant a bitter food, and he’s likely to spit it out.
Taste buds and time
As we age, some body parts lose their strength, so what about taste buds? Researchers certainly agree that taste sensitivity weakens with age, as many a grandparent will attest. The threshold for a particular taste has to be stronger for a 75-year-old to detect than it does for a 25-year-old to recognise. Most studies agree that over a lifetime, the salty and bitter tastes decline more than the sweet and sour tastes.
As the years pass, we seem to have fewer taste buds and fewer taste-receptor cells in each, with 74- to 85-year-olds experiencing the most deterioration. Why? Well, the reason is unclear; however, scientists suspect that age may affect the stem cells involved in taste-bud regeneration. Seeing as you’ve been producing 36 new generations of taste-receptor cells in each taste bud every year for eight decades, this should come as no surprise — that’s nearly 3000 generations of taste buds!
Funnily enough, the taste for chilli doesn’t appear to fade with age. That waving-hand-in-front-of-open-mouth sensation kicks in with the same level of heat no matter how old you are.
Finally, let’s look at saliva, a critical component of taste. A quarter of a century ago, a US dentist described saliva as “not one of the popular bodily fluids. It lacks the drama of blood, the sincerity of sweat and the emotional appeal of tears”. But it’s this workaday nature that makes saliva vital to the taste of foods and to the health of your teeth.
The salivary glands are located near the rear of the mouth (at the sides) and under the tongue. Saliva production is unique to the individual. We can produce anywhere from 500 to 1500ml a day, experiencing the highest flow when we’re eating (or thinking about chocolate!).
Saliva adds liquid to foods so they can enter taste pores, enabling your taste receptors to sense foods’ flavours. Saliva also contains proteins that help these receptors detect the specific tastes of bitter, sweet and umami. In short, saliva introduces your taste buds to different flavours.
When your saliva production wanes and your mouth gets dry, your brain prompts you to drink. But if your mouth is frequently dry, you lose the protective effect of saliva.
You can develop a dry mouth when you’re on certain meds or if you’re regularly dehydrated (because you either sweat a lot, like an athlete, or you drink too much alcohol). Some common symptoms of having inadequate saliva include bad breath, mouth ulcers and tooth decay.
So at your next meal, take a moment to thank your saliva for making the food truly tasty. And why not thank it for helping you lick an envelope or blow a raspberry, too? Can’t do those without saliva either!
How to retrain your taste buds
Okay, so you love sweet foods, and an invisible, but strangely powerful force steers you into every bakery or chocolate shop.
If you’re eating too much cake, ice cream or confectionery, you’d certainly benefit from silencing your sweet tooth, and if your blood pressure is too high, dampening your desire for salty foods would be a good move. But is it really possible to teach your taste buds to fight temptation and be content with less-sweet foods?
The simple answer is yes. Eating food in its least-processed state, sprinkling less salt and avoiding store-bought sauces will help retrain your taste buds.
Tweak your diet like this…
Ensure your diet includes plenty of vegetables, legumes (such as beans and lentils, or homemade hommous made of chickpeas), mushrooms, natural yoghurt and plain milk. With a little persistence, you’ll soon enjoy natural flavours and crave fewer highly flavoured processed foods.
Eat naturally sweet fresh fruit instead of hyper-sweet canned fruit in sugary syrup.
Avoid overcooking your food. Some vegetables, such as broccoli and cabbage, can produce very unappealing odours and flavours.
Many processed foods lack flavour, so we automatically add salt, sauce or dressing to make them more palatable.
The smart approach is to add flavour with herbs and spices. (Remember: As you get older, you may need to add more spice to help you detect some flavours.)
Other processed foods’ flavour is due to added salt, sugar or fat, or to a combination of all three. If you drench your taste buds in added flavours on a daily basis, they’ll have trouble recognising the real flavour of food. (As I write this, a survey has just revealed that Aussies’ favourite snack food is salted potato chips. Fresh fruit didn’t even get a look-in.)
Eat fewer salty foods to shift your preference towards low-salt foods. Of course, taking salt off the table and away from the stove is an important first step.
How soon will my tastes change?
We’re all unique, so retraining our taste buds and food preferences could take as little as two weeks or as long as three months.
Dr David L Katz, director of the Yale-Griffin Prevention Research Center in the US, says that people can switch from full-cream milk to skim milk within two weeks and have no desire to switch back. In Katz’s words, our “taste buds can be rehabilitated”.
When US researchers at the Monell Chemical Senses Center monitored how long people took to reduce their taste for salt, they found that taste buds can change. Within four to eight weeks, study subjects’ taste buds were satisfied with 40 to 50 per cent less salt.
Monell Center director Gary Beauchamp explains that people who cut their salt consumption find it awful at first, but that they become accustomed after a while. Their taste buds simply seem to adapt, as our eyes do in the dark.
Going cold turkey is hard, so try sprinkling less and less salt over a couple of weeks. If you can’t shake salty foods, you’ll only ever be satisfied with high-salt foods or by adding salt to meals, which is bad news for your health.
Since 2005, manufacturers of breads and breakfast cereals have gradually lowered their products’ salt content, often without even telling us. This means that your taste for salt may have already diminished, and that you’re now satisfied with less salt.
Changing your food habits is never easy, but it’s definitely worth it — and age is no barrier to learning new tricks!
The sensation of taste can be categorised into five basic tastes
Sweet: Our preference for sweet foods is normal and starts from our first taste of sweet breast milk.
Sour: Our ability to taste sour foods remains strong as we age, unlike our capacity to taste salt.
Salty: Research suggests that you can halve your preference for salty foods in just two months.
Bitter: Many poisons in nature taste bitter, so an aversion to bitter foods may be protective.
Umami: Robust-tasting savoury foods, such as parmesan, tomato paste and mushrooms, are all umami.