麻豆传媒

Before your Silk Road expedition, what did we know about the evolution of tastes?
We knew that there are groups of genes that respectively regulate the receptors for bitter, sweet, salty, sour and umami taste. We knew that those who have a particular variant of a gene called TAS2R38 taste bitterness more strongly than those who do not have it, for example. And we knew that some of these differences are transmitted from parents to children along genetic lines.

But there is still a lot more to understand, especially about the other four tastes. So on the one hand with this project we wanted to investigate taste genetics more deeply, on the other we were interested in seeing whether there is also a genetic basis for food preference, which is more sophisticated and goes beyond taste. This is something that no one had ever studied before.

Why choose the Silk Road, the network of trade routes between the Mediterranean and China?
Centuries ago, this was an area of incredible human biodiversity. Along this route people have traded and shared everything: cultures, ideas, knowledge, tradition and genes. Then in the 17th century, after thousands of years, trade to India moved to ships and very little exchange occurred along the Silk Road; everything froze, as in a photograph. After that these communities were isolated, they had very little interaction with other populations. So there is great biodiversity, which has crystallised into different and separated groups.

Is the isolation of these groups important for your research?
They are closed communities in which genetic and environmental factors are very homogenous, which makes it easier to see whether 鈥� and why 鈥� there are any specific gene variants that manage to survive in their DNA. The great advantage of having a network of isolated communities is that it also allows you to find rare variants for complex and multifactorial diseases, such as diabetes, that would otherwise be very difficult to detect. From a genetic point of view the Western world is a sort of jam where everything is mixed and those rare mutations get lost.

Why do we need to better understand food preferences?
They determine what we eat, and that has a huge impact on our health, especially in the long run. Conditions such as obesity or type 2 diabetes, which are so widespread today even in children, are largely related to food choices. So this is an important problem.

Of course, we don鈥檛 choose food simply according to taste. Obviously, if you are a supertaster, and can鈥檛 stand strong flavours 鈥� and bitterness in particular 鈥� you might avoid broccoli or Brussels sprouts. But why, among those with a sweet tooth, can鈥檛 some resist ice cream or cakes, when others are less easily tempted? The genetics of taste is not enough to explain these slight differences in preference that, with time, have a sort of butterfly effect on our health.

So what other genetic factors influence how we choose to eat?
Our studies, both on the Silk Road and in isolated Italian communities in the Alps, provide evidence that in addition to input from receptors for smell, sight, sound, touch and taste, food preferences also depend on some genes that trigger neuronal processes related to pleasure and reward. It is the combination of these factors that determines food preference, and so food choice. Until now it was not clear if there was a genetic basis for preference.

鈥淯ntil now, it was not clear if there was a genetic basis for food preference鈥�

Was that because we have assumed cuisine is primarily shaped by society and tradition?
We used to think of preference as being tied to cultural structures 鈥� traditions, handed down habits, the availability of food in a certain environment. For example, in the region of Calabria in southern Italy people eat a huge amount of very hot chilli pepper, while neighbouring regions do not. Why? Was chilli growing there and did the Calabrians鈥� ancestors adapt to eat it and then pass that on by tradition? Or did they start to grow it because they are genetically predisposed to like it? Is it tradition or genetics?

Has your research along the Silk Road answered these questions?
We still have a huge amount of data to process 鈥� we collected DNA samples from 1500 people and are still sequencing their genomes. We need to compare that information with data obtained from tests on perception of colours, scents and sounds, and survey results from a catalogue of 80 foods from which people chose what they like and what they don鈥檛.

But so far, running all this data through supercomputers, we have seen, for example, that there is a variation of the TAS1R2 gene related to preference for alcohol: vodka and white wine in particular. This gene also regulates a sweetness receptor, but rather than only answer the question 鈥淚s it sweet?鈥�, it also answers the question 鈥淒o I like it?鈥� We have also found what we call 鈥淚-like-genes鈥�, for lamb or turnips. In one small Italian community, we identified an 鈥淚-like鈥� gene for ice cream. And interestingly, in mice, this gene is only expressed in the brain and is involved in the reward system.

So, you have identified genes more broadly related to preference, not simply taste?
Yes. Our research on the Silk Road suggests that food preference genes only partially overlap with taste genes. Some have to do with smell. But the majority activate neuronal pathways that regulate pleasure.

鈥淢any food preference genes activate pathways that regulate pleasure鈥�

This article appeared in print under the headline 鈥淎 matter of taste鈥�