Then perhaps the earlier statement denying the existence of evolution was referring to the popular definition that new species arrive from other ones, such as slime to monkeys. Since you also have doubts about that part, then perhaps you don't need to be so harsh about someone else expressing doubts.

The core part of evolutionism, that species change into other species, is something you said you are not convinced about. Is that due to religious conviction? Is religion the only valid reason to have doubts about evolutionism?

Blobbles, I know there are adaptations and changes within species such as you describe, but that is not evolution. Evolution is a theory that claims species mutate into different species, so you can't claim that intra-species variations prove or are part of the theory of evolutionism that claims species change into other species.
By the way, when the dog-breeders design a new breed, are they intelligent designers or unintelligent designers? :)
As for the food issue, perhaps we are now debating nature vs nurture. Personally I think it is about what food we are accustomed to eating in our own lifetime, the type of bacteria we acquire in our own stomachs, rather than bacteria inherited from our ancestors' stomachs. I suspect your friends in Malaysia first ate & still preferred their mother's cooking, even if later they ate it less often. But it is true that research would be needed to verify.

Blobbes, certainly adaptation is a valid concept. Even what Darwin in his excursion to the Galapagos observed was merely adaptation. But evolutionists make extrapolations, claiming that evolution consists of species mutating into different species, which as you said is less provable. Breeding a new breed of dog is not a new species; it's still a dog.
But applying adaptation to food and calling it evolution is ridiculous. If a Chinese baby is born in China but adopted out to the West while still on milk, that child growing up in the West and eating western food, are they evolved through Chinese ancestors to only like Chinese food? If as an adult they return to China and suddenly start eating the food here, would their stomach be genetically less likely to get laduzi than us? I hardly think so.
Let's keep evolutionism out of it.

It's not just Chinese on vacation; I mentioned earlier that I have seen Chinese people living in the West who still just eat Chinese food. But I think that is a cultural difference, that in the West for quite a long time we have had the custom of travel & trying new experiences and cuisines, whereas in China that has only become popular comparatively recently with the rising upper-middle class with disposable income and attitudes a little more open to new things.
And any of us are somewhere on that spectrum, between gastronomically timid and adventurous. Hopefully wherever we're at currently, we can all keep moving up the spectrum.
But talk of individual gastronomic evolution after an expat arrives in China gives me pause. Is that micro-evolution? Or if for example through their diet someone acquires diabetes, is that an evolutionary change? I admit I am a sceptic on evolution, not convinced by creationism/intelligent design nor evolutionism, but this thread has made me even more sceptical!