So this wasn't formerly a problem for me until quite recently. I've noticed that generally deli meat (roast beef or pastrami) is the typical culprit that does this to me. Symptoms include: foul smelling gas and abnormal b.m. post digestion (next day evacuation), and general abdominal pain. Chicken, pork, even fried foods don't generally do this to me. Is it something with beef that just doesn't agree suddenly? I generally eat pretty well (well balanced). One relative (great-grandmother) had celiac, but I thought that meant food just was treacherous no matter what for someone who has that.
Evil smelling flatus is caused by a high sulfate content in the diet. Meat is high in methionine and cystine, and some gut bacteria metabolise these releasing sulfide gases. If these bacteria can be reduced in number, the amount of sulfide gas in flatus can be reduced.
Prebiotics feed some bacteria in the large bowel creating healthy short chain fatty acids which acidify the lower intestinal environment and make it less hospitable for sulfide producing bacteria, thereby reducing the foul smell.