Have you ever wondered why sprouts are the least favourite vegetable at Christmas? Or why a freshly brewed coffee might taste great to you but have your friend pulling a face?
IMB researcher Dr Daniel Hwang has taken a deep dive into taste perception to answer these questions and more – and he can tell us if our taste preference is inherited and by how much.
“Taste is influenced by the interplay between genetic and environmental factors. While it is inherited from our parents, it can still be dramatically changed by environmental influences – your culture, your exposure to a food, an illness causing loss of smell – many things can change your perception.”
Comparing twin tastes
Dr Hwang’s interest in the genetics of taste all started when he worked in the USA and got involved in testing the tastes of identical and non-identical twins.
“The Twins Days Festival is the largest gathering of twins in the world and is held for a few days each year in Twinsburg, Ohio – there’s opportunities for the twins to get involved in research studies. We travelled there with a big box of different taste and smell tests and compared responses from hundreds of twins.”
Twin Studies
Twin studies are used to identify if a trait has a genetic component by comparing identical twins, who share all their genes, and fraternal twins, who share 50 per cent. If a trait is found to be more similar in identical twins, it is more likely due to genetics.
Sweet, sour, bitter, salty, umami, astringent, pungent
The most heritable taste, coming in at 70 per cent inheritable, is the perception of Phenylthiocarbamide (PTC) – a very bitter taste similar to the bitterness found in Brussels sprouts.
“We call people who find PTC extremely bitter super-tasters and they make up 20 to 25 per cent of the population,” Dr Hwang explains.
Everyone has two copies of the bitter taste receptor gene TAS2R38 – one from each parent, and the copies can vary. ‘Super-tasters’ have two functional copies, ‘tasters’ have one and people with no functional copies are ‘non-tasters’.
“Being a super-taster determines your preference for Brussels sprouts and cucumbers – you are also less likely to put salt on your food.”
But in studies of older people, the super-tasters were less likely than their younger counterparts to fuss over the vegies in their roast dinner.
“As we get older, we lose taste buds so Brussels sprouts taste less bitter. We could also get used to the taste, or get to like bitter tastes more or cook our Brussels sprouts differently.”
Youth are more fussy?
To explore this phenomenon more, Dr Hwang studied the tastes of younger Australians, serving up tests to over 2000 people aged 13 to 25 years.
“Young people are less influenced by the environment, so we find that most of the super-tasters respond to the tests as we’d expect – they really don’t like Brussels sprouts.
But why do our genes direct our taste preferences so much?
“The way we perceive food is actually a way for humans to survive,” Dr Hwang explains.
“Humans naturally like sweet because foods that taste sweet are often high in energy – it’s an evolutionary consequence that we look for sweetness to survive. Meanwhile, we don't like bitter, because most of the bitter stuff in nature is toxic and our bitter taste has evolved as a defence system to prevent us from swallowing poisonous foods.”
The danger of bitter
The potential danger of bitter seems to outweigh the lure of sweet, which is only 30 per cent inherited.
Nintendo has harnessed this distaste, using a bitter-tasting agent called denatonium benzoate on Nintendo Switch game cards to stop kids putting them in their mouths.
Other bitter substances include quinine, the source of bitterness in tonic water, and caffeine – your bitter taste perception can determine how much coffee you drink.
When you lose taste
One of the ways Dr Hwang is using his rich treasure trove of taste data to help people is studying how the loss of taste caused by radiotherapy affects cancer patients.
“We’re studying the effects of radiotherapy on taste and appetite – does your sense of taste return more quickly if you are a non-taster, taster or a super-taster?
“It’s hard to eat when you can’t taste, as you can’t be bothered, and we want patients to be eating as healthily and as well as possible during their treatment.”