When Evidence Starts
One common meme lately has been the list of Foods Never to Eat (typical example here). In many of these lists, most of the foods in question do not have actual evidence showing shorter life expectancies or increased illness. They only have far-fetched associations (food X is associated with pesticide Y which is correlated with a syndrome in lab rats that in turn is correlated with cancer). To make matters worse, the lists ignore the fact that toxins have thresholds, below which they're harmless.
The exception is preserved meat. There appears to be actual evidence showing it's unhealthy. The good news is that there is a threshold (just like real toxins) below which it's harmless. Just keep your consumption of pastrami, sausages, etc. below 20 grams per day. (That's five ounces per week for those of us who prefer hexadecimal units.)