It is no longer a secret that synthetic chemical pesticides, insecticides, fungicides, fumigants have a definitive link to chronic dis-orders including various forms of cancer .
The other day while browsing, I came across a very interesting paper by Dr. Ames (famous for Ames test for carcinogenesis) work published in 1990 on Dietary pesticides . According to this paper; 99.9% of the pesticides by weight in American diets come directly from plants – that produces them naturally to defend themselves. Out of which about 27 are found to be carcinogens on rodents!! The authors estimated that an average Americans consumes about 1.5g of natural pesticides every day which is 10,000 times that of the artificial pesticide they consume. This is a startling revelation. The paper further argues that cooking food causes production of few more carcinogenic materials starting from polycyclic Hydrocarbons, heterocyclic Amines, furfurals, Nitrosamines, Notoaromatics. All these really sound scary isn’t it? The paper tells us that nutritious vegetables such as Broccoli, cabbage, cauliflowers and other crucifers can be carcinogenic.
I decided to take a dig on few phytochemicals that have been labeled as carcinogens in this paper:
Glucosinolates (Found mostly in cruciferous vegetables etc.)
Chlorogenic acid(Found in Apricot, Cherry, peach, plum etc.)
Caffeine(Found in Apple, Carrot, Celery, Eggplant etc.)
And majority of Phenolics(Found in Coffee, lettuce, grapes etc.)
From this list, it mainly appears that the vegetables and fruits we considered most beneficial are labeled as potent carcinogens in rodents. There are a very large number of papers published over a period of time, that vows on beneficial effects of the above mentioned fruits and vegetables on cancer. For example:
“Epidemiological studies suggest that brassica vegetables are protective against cancers of the lungs and alimentary tract. Cruciferous vegetables are the dietary source of glucosinolates, a large group of sulfur-containing glucosides. These compounds remain intact unless brought into contact with the enzyme myrosinase by pests, food processing, or chewing. Myrosinase releases glucose and breakdown products, including isothiocyanates….” 
“Epidemiological studies indicate that human exposure to isothiocyanates and indoles through cruciferous vegetable consumption may decrease cancer risk, but the protective effects may be influenced by individual genetic variation (polymorphisms) in the metabolism and elimination of isothiocyanates from the body…” 
“Plant-derived phenolic compounds manifest many beneficial effects and can potentially inhibit several stages of carcinogenesis in vivo. In this study, we investigated the efficacy of several plant-derived phenolics, including caffeic acid phenethyl ester (CAPE), curcumin, quercetin and rutin, for the prevention of tumors in C57BL/6J-Min/+ (Min/+) mice…” 
Chlorogenic acid, caffeine: “Many research investigations, epidemiological studies, and meta-analyses regarding coffee consumption revealed its inverse correlation with that of diabetes mellitus, various cancer lines, Parkinsonism, and Alzheimer’s disease…” 
So, these studies clearly contradict what Ames said in his classic paper. What Ames paper did not touch upon was the bioavailability of the carcinogenic materials derived from natural resources. Moreover, Phytochemicals are not assimilated in the body as pure chemicals. However, somewhere in the middle of the paper, the authors coyly agree that vegetable consumptions do reduce the risk of cancer. When majority of people just read the title and abstract, will definitely get a wrong signal from this paper. I would like to hear more from the readers on this issue.