Betel nuts are carcinogenic and many Asians have developed cancers because of chewing that. I haven't heard any evidence to suggest that chillies are carcinogenic.
There are diseases and cancers that are more common in certain population groups. Some of these increases are because of genetics, such as the prevalence of breast cancer in the Ashkenasi Jews.
South African Asians have a tendency to develop kidney stones. Carribean blacks have increased prevalence of Sickle Cell disease (which affects the blood) and the Japanese have an increased risk of stomach cancer (I haven't verified whether that is genetic or because of some dietary component. Next time I do studies for the Nippon Club I'll find out. Should have asked while I was there).
Now that I think of it, I have noticed increased occurence of kidney stones amongst the UK Asian patients I have seen too.