This very topic recently came up in conversation between myself and a friend who is deeply plugged into the orthodox medical system via the US Army. During a car ride various topics of discussion came up. Along the way I had mentioned the medicinal benefits of Cayenne. Friend replied that the USGov has been studying it as a cause of cancer. At first thought, and in consideration of the causes of cancer that USGov expressly will not study, I was taken aback by the notion. So, I asked "of all the places that need somebody to be looking for causes of cancer, why and how did they end up targeting cayenne peppers?" Details were sketchy but the answer given was that somebody somewhere had informally noticed a trend occurring with people from south of the border where meals cooked with hot peppers is a staple of their culture/diet. This then was enough to give rise to a study (study? studies?... details were sketchy) that in turn linked hot peppers to stomach cancers. This was all impromptu conversation. Details were sketchy and the conversation soon died off.
Under the circumstances, it is important to have some relevant perspective on this "hot peppers might cause cancer" notion. From a historical perspective, the circumstances include various natural food items that, one by one, have been targeted by USGov and the various and often nefarious forces they can bring to bear when they are so motivated to demonize a natural substance. The classic case is Sassafras. It is not exaggeration to say that during the 50's and 60's, the FDA was commissioned to send a few of their hired scientists into lab with the mission to determine how much Sassafras was required to kill a rat. It was eventually discovered that the dose lethal to the rat in question turned out to be literally over a thousands times the quantity that a sane person would ingest during period in which it was administered to the rat...... poor rat :( Of course once the rat succumbed, the FDA then alerted the media "Sassafras kills!" and subsequently set about enacting strict regulations therein.
From a different angle, there are all kinds of relevant questions that arise upon considering the notion "does cayenne pepper cause cancers?". For instance, it would be important to know it the kind of cancers the USGov found by study were due to typically cooked peppers, raw, both, and were they raised using truly legitimate organic methods or via modern methods of big agriculture and new-science science? Lets say for instance that USGove was able to derive cancers from cooked peppers. In this case, all bets are off. In other words, people who cook food, including hot peppers, might still consider that they are eating hot peppers, but this is definitely not a safe assumption. I realize it is well ingrained in many cultures that people cal the foods they eat the same thing as the foods were known to be prior to cooking them. However, cooking tends to drastically alter the forms of items cooked. This is especially the case when food items are cooked using microwaves.
Lets pretend a person puts some actual, real, raw food items - like some rice and beans and cayenne - in a microwave, and then turn on the microwave to cook for several minutes. When they remove the food stuff, they might think it is the same thing that they put into the microwave, which is nice as far as that goes. However, as far as that goes, stuff that comes out of the microwave is no longer the same as what was put into it. Observant people might actually notice that stuff coming out of the microwave visibly bears little resemblance to what it looked like prior. For instance, people who cook hot peppers in a microwave might think they are still hot peppers when they come out of the oven. The aroma might also confirm "yep, MMMMmmm good, cooked peppers", and after they have eaten, it, they might even think they just consumed a fine meal of hot peppers. The thing is, whatever they ate, it wasn't what they thought they ate. To be honest, I do not know that anyone has ever taken the time to formally and officially name the food stuffs cooked in a microwave. The de facto standard seems to be that people have been conditioned to think of / call it the same as what went into the microwave. This standards sort of helps to keep people from discovering the truth involved. Microwaves alter the molecular structure of substances that come in contact with the microwaves (the invisible beams of RF energy oscillating in the range known as "microwave". This is true with other means of cooking, from open fires, to electric ovens to frying pans, but the effect is much more prominent with modernized methods, such as cooking with Radio Frequencies.
Even the USGov and their regulatory agencies, to include FDA and USP, identify substances based on their unique molecular structures. Under a microscope, all natural substances have a known molecular structure; even cayenne peppers. Guess what? Even the USP will not call something "cayenne pepper" if it does not have the known molecular structure of cayenne pepper. What do they call it? I dunno. To repeat, I don't know that they are really interested in this being a topic for public conversation. I suspect they would prefer that people not think about it anymore than they already do and as such they will probably be happy if people continue to call this kind of food stuff the same as what it started out as when raw.
Long story short: there are literally a million and one refined and or synthetic food items that USGov should be studying to as to subsequently report to the public the causes of numerous cancers from many, many common items that have become part of the overall food supply. There are enough of these substances to keep the USGov and their study industry busy from now till doomsday. There are so many of these substances that one really needs to wonder how and why USGov got the idea to study a natural food item when it already has so many, many unnatural items that it is not studying.
Do not fear the humble "cayenne" variety of peppers, especially in their natural state; raw, non-GM'd and preferably organic. Eat them, drink them, put them on your body and in your body as necessary, often and repeatedly. You can even use them in unnaturally kicked up forms; tinctures. Meanwhile, live well, live healthy, live long and do not fear the pepper. If anything, fear those sowing fear of things like peppers. This you can take to the bank. Better hurry while you can find a bank that is still open. Perhaps you have noticed that banks too have recently been observed as trending towards developing cancers, but as far as I know, these kind are not being blamed on harmless natural substances like peppers.... that would be quite a stretch, but as far as I know, official studies have shown the cause to be "credit crunch". LOL!