ABSTRACT
Introduction .......................................................................................... 138 Natural Plant Toxins in Foods ............................................................. 138
Canavanine ....................................................................................... 138 Cyanogenic Glycosides .................................................................... 139 Allyl Isothiocyanates........................................................................ 140 Hydrazines and Other Toxins in Edible Mushrooms ..................... 141 Toxic Substances in Spices and Flavoring Agents .......................... 142 Pyrrolizidine Alkaloids .................................................................... 145 Substances in Bracken Fern ............................................................. 148 Acetylcholinesterase Inhibitors in Potatoes.................................... 149 Tannins .............................................................................................. 150 Caffeic Acid and Chlorogenic Acid ................................................. 151 Coumarin and Psoralen ................................................................... 152 Miscellaneous Flavonoids: Quercetin, Ellagic Acid, Kaempferol, and Rutin .......................................................................................... 152
Natural Chemopreventives in Plants .................................................. 153 Introduction ...................................................................................... 153 Isothiocyanates ................................................................................. 154 Indole 3-Carbinol ............................................................................. 154 Polyphenols ...................................................................................... 155 Miscellaneous Chemopreventives ................................................... 156
Conclusions........................................................................................... 157 Acknowledgments ................................................................................ 158 References ............................................................................................. 158
Our food contains, in addition to the many well-known major (protein, fat, carbohydrate, and fiber) and minor (vitamins, minerals, and nonessential compounds) nutrients, thousands of naturally present toxic plant compounds. Some are known or strongly suspected to cause cancer in laboratory animals and, thus, may be potentially carcinogenic in people. Many of these compounds are commonly termed “nature’s pesticides” because they are often toxic to predators, such as insects and animals, thereby conferring a competitive advantage to the plant that produces them. Other natural toxins in plants have no known role. Although these chemicals are in every meal we eat, they have received little attention compared to that given to minute residues of synthetic chemicals such as PCBs and pesticides. Our food contains significantly greater amounts of natural plant toxins and carcinogens than the synthetic kind, and our bodies aren’t able to distinguish between the two. Still, while popular notion remains that “natural is good,” it is clear that natural toxins pose a far greater health risk than that posed by synthetic chemicals in our foods.
