That obviously depends on the type of cancer. Smokers are way more likely to get lung cancer but for other types of cancer with high mortality rates (prostate, breast, myeloma, lymphoma etc) there is no single attributable 'exposure' that is known to be the cause.
The link to lung cancer is the most high profile (and rightly so -- 80% to 90% of all incidences of long cancer are primarily attributed to smoking), but its carcinogenic effect can be seen all over the body.
Note: Obviously I'm not advising anyone to smoke.
* Eating red meat
* Eating processed meat
* Drinking 3+ glasses of milk daily
* Inadequate levels of vitamin D
These are all well-known to the nutrition community to increase cancer risk.
I think it's overstating it a bit so say those things are "well-known". There are some indications that those things may result in slight increases of risk for certain types of cancer.
I would seriously question the credentials of any PhD nutrition researcher at a decent university that disputed any of those factors.
Huh? There's some correlation with prostate cancer[1] but that's it.
[1] http://www.pcrm.org/health/health-topics/milk-consumption-an...
"The risks of a high-protein diet are even comparable to smoking, the researchers said."[1]
1: http://www.scientificamerican.com/article/diet-high-in-meat-...
http://www.marksdailyapple.com/will-eating-red-meat-kill-you...