If you eat sensibly now don't add to your worries - go on eating sensibly. Not too much red meat, no ground and grilled meat, lamb more often, beef less frequently, organic meat if you can afford it. FAR more fresh vegetable and fruit - not less than 5 portions a day.
Increase fluid intake, minimise coffee and tea, erradicate spirits and avoid toxins like Coke and trans fats.
NEVER add salt to anything and reduce sugar intake. Avoid ALL narcotics, eschew tobacco in any form.
Careful not to take yourself too seriously or you will die young of stress, ulcers or boredom.
I'll stand by theory - yes the theory is backed in some instances by statistical probability. Beer is a generic that varies from the chemically produced fizzy canned drinks called beers and lager through massively mass produced beers shipped in aluminium kegs to beers in burnt oak barrels and those that complete fermentation in glass. Yep Theory!
Whether the beer is in some way profilactic or the increase in fluid intake is the beneficial aspect is completely unknown.
You condemn tap water!
Tap water varies dramatically what aspect of tap water concerns you?
Bottled water of course has its own problems as much of it is in plastic bottles where with some plastic bottles leachate of softners have been found to be carcinogens!
Most water supplied publicly is mildly chlorinated - life is all trade offs would you rather die, for certain, of the bugs in tap water or consider the theory that tap water MAY give you cancer!
One must be careful not become yet another false cancer statistic where the FEAR causes such stress that you push your BP so high you blow your pump or one of the pipes [coronary or annurism - you choose].
A very high percentage of Cancer survivors kill themselves by creating FEAR and STRESS for themselves.
Consider for a moment King Henry VIII, rumoured to have died of syphilis due to the massive ulceration on his legs that first crippled him and then meant he stank of gangrene, this was NOT syphillis. It is now known that because, as King, he had to display his wealth this he did by eating great quantities of meat - he died of mal nutrition as he NEVER ate any vegetables or fruit!
We must be very carefull that we do not metaphorically study our cancers such that we pay so much attention to the latest report we receive that we walk under the front wheels of a bus due to concentrating on reading the report! ;D