From earliest time people have been aware that some plants are poisonous and should be avoided as food. Other plants contain chemicals that have medicinal, stimulatory, hallucinatory, or narcotic effects. In the past 50 years, great strides have been made in understanding nutrition and the role it plays in human health. Federal agencies, such as the Food and Drug Administration, Department of Agriculture, and Enviromental Protection Agency, as well as many state and local agencies, are charged with interpreting and enforcing laws dealing with the safety of the food we eat and the water we drink. The food supply in the United States is widely recognized as safe, economical, and of high quality, variety, and abundance.
             Despite these efforts, concerns remain that some dietary components may contribute to the problem of cancer in humans. Cancer-causing chemicals that occur naturally in foods are far more numerous in the human diet than synthetic carcinogens, yet both types are consumed at levels so low that they currently appear to pose little threat to human health. The greater cancer threat in the human diet today comes not from minor chemicals in food, but from diets too rich in calories and fats, or alcohol. (NRC Report 1)
             Since the 1930's, scientists have recognized that the occurrence of certain cancers may be related to substances in the diet or to patterns of food intake. They have also recognized that some chemical components of food either initially present in the food, formed during preparation (more likely in cooking), or added for preservation or presentation are capable of generating tumors in high-dose rodent tests. Early studies on chemicals that cause cancer were carried out to determine what levels of exposure to specific chemical, such as polycyclic aromatic hydrocarbons (PAHs) and certain food colors, such as butter yellow, resulted in the formation of cancers in the liver and gastrointestinal tract o...