Harold McGee is a noted food scientist and the author of several books including On Food and Cooking and The Curious Cook.
The tomato belongs to the nightshade family and it is widely believed that the leaves are toxic. Harold says that there is no evidence to back that claim. Instead, tomato leaves contain the alkaloid tomatine, which helps lower LDL cholesterol levels.
Harold has used tomato leaves in pasta sauces and in pestos. Read about it in The New York Times.