Ever thought about the lack of tomato leaves in markets and their absence on our dining tables? I thought about this the other day, when the vines of tomatoes that I planted in a vase reached up to the windowsill and began producing teeny red tomatoes.
The tomato vines with their bright green leaves made me think of how unfairly they are treated despite having such a sharp, pungent, essentially ‘tomatoey’ smell. The conventional wisdom is that tomato leaves are not edible; but why so?
While it is true that many members of the nightshade family, Solanaceae, to which tomatoes belong, contain large amounts of alkaloids that make them highly toxic, inedlible and indigestible, this is not true of tomatoes or their leaves.
In fact, the Aztecs and Pueblo (Native Americans) people of Central America, where tomatoes were originally cultivated, believed tomatoes were invested with magical properties and that those who ingested tomato seeds were blessed with powers of divination.
However, not just tomato leaves, even tomatoes were for long considered inedible in Europe and elsewhere. In Florence and in several other areas of Italy, tomatoes were earlier used solely as a tabletop decoration before it became incorporated into the local cuisine in the late 17th or early 18th century.
Today, we know that though tomatoes belong to the very large and diverse nightshade family, they definitely are not of the deadly nightshade variety. In fact, many cultures eat different varieties of nightshades, in some cases as staple food, including potatoes, eggplants or aubergines and capsicum, both chili peppers and bell peppers.
The levels of tomatine (the toxic glycoalkaloid) in foliage and green (unripe) tomatoes are generally too small to be dangerous unless they are consumed in large amounts as greens. In fact, small amounts of tomato foliage are sometimes used for flavoring without any ill effects, and the green fruit is often used for cooking, particularly as fried green tomatoes.
The amount of alkaloids in tomato leaves and the green fruit is so negligible that both have the same level of edible safety. In addition to that, glycoalkaloids are so poorly absorbed by the gastrointestinal tracts of mammals that they pass out quickly through urine or feces. The maximum that excessive consumption of glycoalkaloids could do is to cause mild stomach irritation.
According to a food safety study by The Journal of Nutrition, which compared the potential toxicity of glycoalkaloids found in tomatoes, potatoes, and eggplants, tomatine is a relatively benign glycoalkaloid. The study revealed that there was no significant change to liver weight or body weight when tomatine was fed to mice, and it is now not considered adverse to human health.
Tomatine itself is found to kill or suppress human breast, colon, liver, and stomach cancer cells. The US Department of Agriculture's research shows specific benefits of tomatine and suggests developing ‘high-tomatine’ red tomatoes to study their potential in treating cancer and as an anti-carcinogenic and anti-viral agent.
Although some organic gardeners make anti-pest sprays from chopped tomato leaves soaked in water, this does not imply that the leaves are harmful to humans. The tomatine present in the leaves serve as a self-defense mechanism to ward off pests and is of no harm to anyone except those allergic to tomatoes.
But despite all the science behind it, tomato leaves are still not seen in markets and mainstream cuisines, not because they are necessarily toxic but because many people just do not know what to do with them.
True, if you tried to Google recipes for tomato leaves, you are unlikely to come across any. Former Chez Panisse chef, Paul Bertolli is known to infuse his tomato sauces with tomato leaves, but aside from that, not many people have stepped up and confessed to their culinary use.