6. Hormone-filled milk
Thanks to genetic engineering, cows can produce twice the amount of milk when compared to 50 years ago. This is done by a synthetic hormone called recombinant bovine somatotropin, or rBST that stimulates the production of more milk. The hormone is banned in Europe as it has been linked to prostate, breast and colon cancers. It is still legal in the USA, although dairy farms are being pressured to stop using this hormone.