Many people worry about the carcinogens in their daily food. Cancer can occur when a cell divides if , when the DNA is duplicated, there is an error in transcription. A cell can then occur that reproduces uncontrollably, without contact inhibition or showing the Hayflick effect. The uncontrollable reproduction is a hallmark of all cancer cells. Thus cancer cells are truly immortal. The error in transcription can occur spontaneously, as a true mutation, or be induced by an outside process, called a carcinogen. The carcinogen can be a naturally occurring chemical, a man-made chemical, external energy (e.g.X-rays), it can be a chronically irritative process that stimulates the cell to divide, and thereby increases the chance of a mutation, or it can be a virus. To be technically correct, most carcinogens are inducers, i.e. they either increase the chance of a mutation or they increase the susceptibility of the cell to outside mutating influences. A few carcinogens directly cause cancer, but none of them will do so in 100% of the cases.
The first carcinogen was discovered by Dr. Percival Pott, a London physician (after whom Pott's Disease, aka tuberculosis of the spine, is named). He observed that London chimney sweeps (who generally started working when they were young boys, because of their size) almost invariably developed cancer of the skin of the scrotum, an extremely unusual cancer, at a very young age. Since they never bathed or could afford to change their underwear, he hypothesized that chronic contact with chimney soot was the inducer. By the simple expedient of having them wash their underwear weekly to remove the soot, he virtually eradicated this disease. His epoch discovery should be as well known as the story of the water pump handle and the cholera in London.
We all know that cigarette smoke is an inducer for lung cancer, as is exposure to radon, a radioactive gas, by uranium mine workers. Uranium workers who smoke have a synergistically enormously high rate of lung cancer. What is less well known is that 100% of smokers develop COPD, or emphysema, and sophisticated pulmonary function tests always show an abnormality in the closure of small airways in all smokers.
Radiation is considered to be carcinogenic, viz. Madame Curie, but consider cosmic rays. They are extremely high energy gamma rays reaching the earth from outer space. Denver, which is a mile high, has much less atmospheric protection from these high-energy rays than does New York City, yet their cancer rates are not significantly different.
The HIV virus is a significant inducer for Kaposi's sarcoma, the infectious mononucleosis virus for Burkitt's lymphoma, Hepatitis C virus leads to cancer of the liver (as does any process that has caused cirrhosis) and no doubt there are other cancer-inducing viruses waiting to be discovered. (Yes, I know this is not a complete list.)
However, a main human concern seems to be carcinogens in our food. Now, how do we decide that a chemical is carcinogenic? We usually assume that any chemical that causes cancer in rats, no matter at what dose, is carcinogenic. The fact that rat physiology and human physiology are different does not enter into our considerations, although their are chemicals that induce cancer in rats and not in humans , and vice versa.
Just to emphasize human-animal biochemical and physiological differences: only man and the guinea pig need Vitamin C in their diet; all other animals have the enzyme to synthesize it. Only the Dalmatian dog breed can get uric acid kidney stones, because other dogs excrete a different protein breakdown product in their urine. Many animals carry viruses that cannot affect or infect man, and some viruses that co-exist in animals can be lethal for man (e.g. swine flu).
Representative Delaney, from New York, had the Delaney clause added to a bill in Congress. This clause stated that any chemical that caused cancer in lab rats, could not be added to food. Of course, as soon as saccharine, the only available sweetener was shown to cause bladder tumor in rats, Congress immediately passed a saccharine exception to the Delaney clause.
Dr. Bruce Ames, a noted biochemist also developed the Ames test, which looked for DNA damage to bacteria in a Petri dish to determine possible carcinogens.
However, Dr. Ames also pointed out that there are many rodent carcinogens that occur naturally in vegetables, because the vegetables apparently develop these chemicals as their own pesticides. In other words, almost all vegetables contain carcinogens which, if extracted from the vegetable would be illegal to add to food, but the whole vegetable can be. How many of you remember when coffee was thought to induce cancer of the pancreas, or that preparing hot tea with lemon in a styrofoam cup liberated a carcinogen?
In any event, in the interests of completeness, the following is a partial list of everyday vegetables that create and contain their own carcinogens, even if you wash all the pesticides off:
and soy lowers men's sperm count (it contains a phytoestrogen)