We use green coffee beans as the source of our caffeine.
When coffee beans are picked and removed from the fruit they're inside, they're a pale to light green in color.
It's only after they're roasted that they take on a dark or light shade of brown and develop that wonderful aroma that we associate with comfort and feeling alert.
But that cooking process creates byproducts. One of the chemicals formed when coffee is roasted is acrylamide, a substance discovered in 2002 by Swedish scientists.
Acrylamide is considered "probably carcinogenic" by the International Agency for Research on Cancer, and California considers it a substance that's "known to cause cancer."
3. Live Science