Confession time: I’m just a tad partial to chocolate. I blame my Dad who also qualifies as a chocoholic. But I’ll never forget a chocolate experience I had almost 20 years ago when I was given the opportunity to try some Gymnema sylvestre. Some what you say? It’s a herb, native to Indian and Sri Lankan forest that suppresses your ability to taste sweetness. And eating chocolate straight after the herb was extremely offputting. The chocolate had virtually no taste but had the texture of wax, or maybe soap. I could feel it coating my tongue and teeth and I couldn’t imagine ever wanting to eat chocolate again. That’s the power of our taste buds.
The famous five
You didn’t know it, but you were already developing preferences for particular flavours before you were even born. The food flavours you were introduced to in the amniotic fluid you were surrounded by before birth influenced you, as did the diversity of flavours in breast milk if you were breastfed.
These days you probably take for granted that you can taste a massive variety of flavours. But in fact, you have only taste buds that respond to five distinct tastes: sour, bitter, salty, umami (savoury) and sweet. Some researchers argue that fat should be considered a sixth primary taste.
At a basic level, your taste buds are there to make sure you eat nutritious things and avoid poisons. Each of your taste buds contains a group of 50 to 150 taste receptor cells that look a bit like a tightly-closed bunch of bananas. Taste receptor cells sample the food molecules in your mouth and report a sensation of taste to your brain. The complex flavours you taste are a result of both the taste and smell of food.
If you have a close look at your tongue in the mirror, you’ll notice lots of little pale bumps all over the surface. These are called fungiform papillae. Your taste buds are too small to see without a microscope but they can be found on these papillae. There are also taste buds on the roof of your mouth and on your throat. And you’ve got somewhere between eight and ten thousand taste buds which are replaced about every two weeks.
Are you a super-taster?
We used to think different parts of the tongue handled different tastes – for example that receptors for sweet were located on the tongue tip and the bitter region was at the back of the tongue. But we’ve known since 1974 that all taste buds can detect each of the five basic flavours.
What does differ though is the number of taste buds each person has. If you’ve got a particularly picky eater in your family, consider there may be something more than fussiness going on. Some people have many more taste buds than others and therefore have much stronger likes and dislikes of foods. These people are termed ‘super-tasters’.
If you’re one of the 15 to 21% of people who can’t bear to eat coriander and say it tastes like soap you can blame it on your genes. Researchers have identified several genes involved in taste and smell that seem to be responsible for peoples’ complete hate of the herb.
Of birds and cats
You are most likely accustomed to enjoying the full range of tastes but recent research has shown that not all animals get to enjoy the same diversity of flavours.
It seems penguins can only taste sour and salty and have completely lost the ability to detect sweet, bitter or umami flavours. Researchers worked this out when studying penguin DNA. They were looking for the genes that enable taste buds to pick up each of the five different tastes and found a number were missing. It’s possible this ability was lost as a result of penguins living in very cold environments. Research suggests receptors for these three tastes don’t work at very cold temperatures so over evolutionary time the genes have been lost. It was probably important that penguins maintained their ability to taste salt so they could keep track of their salt intake from the ocean and being able to taste sour would help a penguin avoid rotten food. But beyond that it seems a penguin’s palate is not tuned to fine dining.
In fact, research suggests all birds have lost their ability to taste sweetness. But in a fascinating twist scientists have found that hummingbirds, specialist nectar feeders, have repurposed their umami receptors so they can taste sweet.
And it isn’t just birds that have lost the capacity to taste sweetness. Unlike almost all other mammals studied to date, cats don’t have the ability to taste sweetness. Presumably being able to taste sweet is of little value if you never eat any fruit or vegetables. Tigers, lions, panthers, your tabby at home, none of them can taste sweetness.
Being able to taste the delicious sweetness of chocolate brings me so much joy I’m glad I’m not a cat. Because as I discovered all those years ago, chocolate without sweetness just isn’t chocolate. No thanks.
Links and stuff
- Find out if you are a ‘Supertaster’
- Our ability to taste fat and links to obesity
- Ask Smithsonian video: how do taste buds work?