Diet is estimated to account for 30–35% of all cancer deaths — making it the single largest modifiable cancer risk factor after smoking.

Foods associated with increased cancer risk:

• Processed meats (bacon, sausage, hot dogs) — Group 1 carcinogens. Each 50g/day increases colorectal cancer risk by 18%.
• Red meat — Group 2A (probably carcinogenic). Limit to <500g/week.
• Alcohol — Group 1 carcinogen. All types.
• Excess body fat — linked to 13 cancer types

Foods associated with reduced cancer risk:

• Cruciferous vegetables (broccoli, cauliflower, Brussels sprouts) — contain sulforaphane
• Fiber — reduces colorectal cancer risk
• Lycopene (tomatoes) — linked to lower prostate cancer risk
• Green tea polyphenols

Key insight: No single food prevents or causes cancer. Overall dietary patterns over decades are what matter.

Reference:

Wikipedia: Cancer and diet

https://en.wikipedia.org/wiki/Cancer_and_diet