A 2013 study published in the British Journal of Cancer, revealed that natural redheads had a reduced risk of developing prostate cancer compared to all other hair colours. The reduced risk was roughly half of that of all other hair colours.
This is a one of a kind study and the results need to be interpreted carefully. The study was conducted on the back of a larger study of Finnish men aged 50-69, all of whom were smokers. The original study was looking at the effect of various supplements on cancer incidence. The results relating to hair colour came from a follow-up questionnaire, which ascertained a number of character traits from the participants. The total number of men involved in the study was almost 21000.
The mechanism for why the reduced risk occurs in redheads is not well understood. It is believed to be linked to changes in the MC1R gene, which is associated with having red hair colour.