I recently had an armchair expert tell me that french press style coffee vs a filtered coffee preparation method increases your risk of cancer. [Don't confuse french press coffee for the biological apparatus]. This person was foggy on the details but indeed got rid of their Bodum(tm). Personally I find coffee from a french press tastes superior, but then again, I'd drink it off a dog some mornings. Some googling revealled one source of the idea that unfiltered coffee increases your risk of cancer the source they cite is an article that shows increased homocysteine levels in drinkers of unfiltered coffee vs NO COFFEE. (no coffee?!?!) Homocysteine itself is not directly derived from your diet, however, high levels in the blood are indicators for high risk of heart attack and stroke, and possibly cancer. The thought was that filtering coffee removed what the authors assumed was causing the rise in homocysteine levels. Turns out filtering coffee doesn't change the fact that drinking coffee raises homocysteine levels.
To me this is a good example of something I see often, that is, cancer research NOT serving the public who funds it. If this is the crappy way that the public is informed about cancer research I'm surprised it still is funded. Someone gets rid of their french press because their concerns for their health based on the mainstream medias reporting of an incorrect assumption in the literature. What is also strange is that the damage is done. I think I would have a hard time convincing this person that their french press coffee is no worse for them.
Also I think there is a leap of logic here that I have heard is similar to the leap in logic made for the statin class of drugs. That is that since higher homocysteine levels correlate with higher risk of cancer (let's assume the one article I found linking the two is correct), then homocysteine is a cause of cancer. An indicator is not necessarily the cause but is merely associated with increased risk.
Also it may be that coffee raises cancer causing homocysteine levels by an appriciable amount, however, other factors associated with coffee drinking may result in an overall reduction in cancer incidence. So again even if homocysteine causes cancer, coffee may not.
Of course, perhaps coffee has so taken over control of my thought processes that I am in denial.