On Food and Cooking

particular sulfur compound (a thiazole).
Because tomato leaves have a pronounced
fresh-tomato aroma thanks to their leaf
enzymes (p. 273) and prominent aromatic oil
glands, some cooks add a few leaves to a
tomato sauce toward the end of the cooking,
to restore its fresh notes. Tomato leaves have
long been considered potentially toxic
because they contain a defensive alkaloid,
tomatine, but recent research has found that
tomatine binds tightly to cholesterol
molecules in our digestive system, so that the
body absorbs neither the alkaloid nor its
bound partner. It thus reduces our net intake
of cholesterol! (Green tomatoes also contain
tomatine and have the same effect.) It’s fine,
then, to freshen the flavor of tomato sauces
with the leaves.